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luseboy

Running cool (maybe?)

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Alright so I haven't been on here much lately because I've been busy sorting out all the little issues with my car after getting it on the road.  It's been having a weird thing happen where it runs at 150 degrees even though it's got a 180 degree thermostat in it.  It also seems to take awhile to warm up.  Even still, if I'm sitting in traffic or whatever it will creep up to 205 or so and hold there.  I suspected that the thermostat was stuck open, so today I replaced it and tested the old and new thermostats, both of which seemed to work fine although the old one didn't close back up till about 170 degrees while the new one was closed at 178.  With the new thermostat it runs at maybe 155-160, slightly warmer, but still too cold.  The engine is an L28 (F54/P79), it's got a 240z thermostat housing on it, with a universal 3-core aluminum radiator, dual electric fans (one set to turn on at 185 degrees, the other on a toggle switch), and an auto meter water temp gauge/sender.  The sender is tapped into the same location it would be on a stock 240z (right behind the dizzy).  One thing I just remembered is that the temp sender is 1/8 NPT while the Z housing is 1/8 BSPT, so there is an adapter between them which makes the sender stick a little further out than it would normally.  I'm fairly sure I have the cooling system well bled, but not positive.  Anyone have any ideas what else could be causing my car to run cool?  Is it possible that the radiator is cooling too well for normal street driving?  Does anyone have any experience with temp senders being weird if they're on an adapter? I'm stumped, any other ideas what rabbit hole I should try and crawl into next? I should note too that the temp fan only comes on when the gauge reads over 185, so it seems that the gauge is at least somewhat within the range of accurate.  Also I should mention that even when the gauge is at 150 the heater still blows quite warm, just as warm as I would expect in any stock car really.

Thanks!

Edited by luseboy

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1 minute ago, HuD 91gt said:

How are you getting your temperature readings?

Using an Autometer temperature gauge with the sender in the thermostat housing on the end of a BSPT to NPT adapter.  I don't have an infrared thermometer to confirm the readings with but I should probably get one.  

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Well a really long adapter might can act as a heat sink, but it shouldn't cause that much of a difference unless it is sticking way out there or getting a lot of air or something to keep it cooler then the coolant.

How's the fuel mixture? Oil smell like gas? If you are running really rich all the time that may be a small factor.

Does the fan have its own temp probe? Or is it taking the signal from the one sender?

A well sorted system can stay pretty cool. I know my intercooler is cold to the touch on hot days if I've been running for a while. If you got an oversized radiator with a high FPI count you just might be cooling it a bit more then you expect. I think when I had my L28 it sat around halfway on the gauge which looks like it is at 180 or so. That was with a champion 2 row radiator with e-fans and no shroud. I could imagine with a shroud and an extra row of cooling with more FPI it might have sat lower.

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35 minutes ago, seattlejester said:

Well a really long adapter might can act as a heat sink, but it shouldn't cause that much of a difference unless it is sticking way out there or getting a lot of air or something to keep it cooler then the coolant.

How's the fuel mixture? Oil smell like gas? If you are running really rich all the time that may be a small factor.

Does the fan have its own temp probe? Or is it taking the signal from the one sender?

A well sorted system can stay pretty cool. I know my intercooler is cold to the touch on hot days if I've been running for a while. If you got an oversized radiator with a high FPI count you just might be cooling it a bit more then you expect. I think when I had my L28 it sat around halfway on the gauge which looks like it is at 180 or so. That was with a champion 2 row radiator with e-fans and no shroud. I could imagine with a shroud and an extra row of cooling with more FPI it might have sat lower.

I think the sender is designed to be immersed in coolant, but I think with the adapter only the tip of the sender will be fully immersed.  I was thinking maybe an air bubble is trapped in there, but I've heard of other people running the same setup with no problems and I don't have any other symptoms of a cooling system that needs to be bled really but I think this could be the case.  Another possibility is that the adapter allows for some pocket of coolant around the sender that isn't moving even when the thermostat opens and is staying cooler, but that seems really far-fetched and the pocket would heat up to it's surrounding temperatures pretty quick.

The fuel mixture is what I'd call significantly less than optimal, however it is only super rich in certain conditions (I have a 4bbl on an AZC manifold that I'm still working on getting running right).  The oil did smell like gas until I hooked up a PCV system, but has smelled normal since then.  The way I have it tuned right now, the A/F ratios hover around 12-14 throughout most conditions.  

The fan does have a separate temperature switch, which I think came out of a honda of some sort.  It is on a different port on the thermostat housing.  

The rad is technically undersized, but it's a really thick core and it is crossflow if I remember correctly.  I was going to ask if it's possible that my radiator is "overcooling" but this seems unlikely.  Maybe everything's fine and this is how it should be, but I feel like the car would run smoother (and better overall probably) if it was running at the right temp.  150-160 just seems too low of a running temp, but maybe it's fine?  If all this thread gives me is some peace of mind I'm totally fine with that. 

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2 hours ago, luseboy said:

 It's been having a weird thing happen where it runs at 150 degrees even though it's got a 180 degree thermostat in it.  It also seems to take awhile to warm up.  Even still, if I'm sitting in traffic or whatever it will creep up to 205 or so and hold there.

With the new thermostat it runs at maybe 155-160, slightly warmer, but still too cold.  The engine is an L28 (F54/P79), it's got a 240z thermostat housing on it, with a universal 3-core aluminum radiator, dual electric fans (one set to turn on at 185 degrees, the other on a toggle switch), and an auto meter water temp gauge/sender.

I should note too that the temp fan only comes on when the gauge reads over 185, so it seems that the gauge is at least somewhat within the range of accurate.  Also I should mention that even when the gauge is at 150 the heater still blows quite warm, just as warm as I would expect in any stock car really.

Is your fan on a temperature switch or does it use a controller?  Where is its sensor located.

The fact that the temperature creeps up to 205 shows that you have a cooling problem.  The thermostat is actually a heating device.  It stays closed until coolant temperature reaches its set point.  But the coolant has to flow past the thermostat in order for the thermostat to equilibrate to the same temperature.

So you actually have two odd problems.  Do you have your heater core bypassed?  Maybe the pump isn't pushing enough coolant to heat up the thermostat, with the bypass, and also not pushing enough to cool the engine.

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Just now, NewZed said:

Is your fan on a temperature switch or does it use a controller?  Where is its sensor located.

The fact that the temperature creeps up to 205 shows that you have a cooling problem.  The thermostat is actually a heating device.  It stays closed until coolant temperature reaches its set point.  But the coolant has to flow past the thermostat in order for the thermostat to equilibrate to the same temperature.

So you actually have two odd problems.  Do you have your heater core bypassed?  Maybe the pump isn't pushing enough coolant to heat up the thermostat, with the bypass, and also not pushing enough to cool the engine.

Haha you replied while I was replying. It uses a temperature switch that was oem on some other car (A honda of some sort), located on a different point in the thermostat housing.  

It's odd huh?  It's either too hot or too cold.  Every once in awhile it will stick around 180 for a bit, but once I start moving above 30mph for more than 5 minutes it's back to 150-160.  This makes sense, it seems that it isn't equilibrating properly for some reason.

I have a universal hot rod heater from summit or jegs, it's a pretty large core and I just have a little manual shut off valve that I pretty much always leave open.  When I had the engine apart, I opted to reuse the water pump because it looked to be in great shape. Perhaps I missed some detail, but it had no play, no indication of any leakage, no messed up fins, and it spun nicely.  When I first filled the system with coolant I left the cap off and brought it up to operating temperature and suddenly had a gallon of coolant on the ground that rushed out of the open radiator, leading me to think the pump is definitely moving coolant.  Of course, I realize that none of this gives any actual indication of water pump health but it seems unlikely to me.  

This does bring up an interesting thought though, could the heater be plumbed wrong and causing these issues? I have one side of the heater core connected to the passenger side water inlet, and the other side connected to a big NPT port between cylinders 5 and 6 on the head on the passenger side as well.  I remember looking into this and thought it was an okay way to run it but maybe I missed something then.  

 

 

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6 minutes ago, luseboy said:

I have a universal hot rod heater from summit or jegs, it's a pretty large core and I just have a little manual shut off valve that I pretty much always leave open. 

When I first filled the system with coolant I left the cap off and brought it up to operating temperature and suddenly had a gallon of coolant on the ground that rushed out of the open radiator, leading me to think the pump is definitely moving coolant.   

This does bring up an interesting thought though, could the heater be plumbed wrong and causing these issues?

The coolant gushing out problem just came up in another forum I hang out on.  I had the same thing happen with my old clogged radiator.  I think that it means that the radiator is not passing enough fluid to supply the pump inlet.  The bottom hose has to be collapsing, causing an overall system volume decrease, and the coolant gets pushed to the top side.  But the gushing is a sign that the thermostat opened.

First though, you might try just closing the manual coolant flow valve through the core completely, and see what effect it has.  It should force more fluid through the block and head and thermostat housing.  If you see an effect it will be a clue about at least one of your problems.

 

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1 hour ago, NewZed said:

The coolant gushing out problem just came up in another forum I hang out on.  I had the same thing happen with my old clogged radiator.  I think that it means that the radiator is not passing enough fluid to supply the pump inlet.  The bottom hose has to be collapsing, causing an overall system volume decrease, and the coolant gets pushed to the top side.  But the gushing is a sign that the thermostat opened.

First though, you might try just closing the manual coolant flow valve through the core completely, and see what effect it has.  It should force more fluid through the block and head and thermostat housing.  If you see an effect it will be a clue about at least one of your problems.

 

Interesting, I didn't realize this was a problem.  I had filled the block and head through the thermostat housing and topped off the radiator before running the engine and getting it up to temp.  It very suddenly started gushing out of the top of the rad, presumably when the thermostat opened.  I guess if nothing else it shows that coolant is flowing lol.

Yeah I was just thinking that.  I actually just drove around for a bit to see if I noticed anything else but didn't close off that valve.  I think I drove it around with the valve closed off for a few days months ago but I don't remember the temps being any different, I'll have to try that again.  I'm at a loss as to what else could be causing it to run cool though.  I can't imagine my cheap aluminum radiator is cooling too much for the L28, is this even realistically possible to this level?  

 

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The thermostat staying shut will cause the engine to heat up no matter what radiator you have.  It's the only outlet from the head and engine.  High pressure from a good pump might cause a bad thermostat to blow open though.  Couldn't tell if your "new" thermostat was new new or new old.

If you're using old thermostats try getting a new Nissan brand thermostat and starting over.  You might improve getting to operating temperature but still have the creeping to 205 problem.  They still have cross-reference charts to new thermostats.  You can get one at your local Nissan dealer.

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43 minutes ago, NewZed said:

The thermostat staying shut will cause the engine to heat up no matter what radiator you have.  It's the only outlet from the head and engine.  High pressure from a good pump might cause a bad thermostat to blow open though.  Couldn't tell if your "new" thermostat was new new or new old.

If you're using old thermostats try getting a new Nissan brand thermostat and starting over.  You might improve getting to operating temperature but still have the creeping to 205 problem.  They still have cross-reference charts to new thermostats.  You can get one at your local Nissan dealer.

The first one was a brand new stant unit. The one I got today is a brand new motorad cheapie that I got in case I needed it. I tested both of them to get some comparison between them, they both seem to work properly in hot water.  

I'm thinking the creeping problem is probably a fan problem. Is there a known rule of thumb for an acceptable amount of creep in high heat situations like traffic in the summer? I'm not convinced that a different brand of thermostat will fix this at this point.  I'm sure the Nissan thermostats are much better, but I would think these should function well enough to be used in an otherwise up-to-par setup in normal conditions without too much of an issue, right? 

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Do you have any of the bypasses blocked?    Which side of the thermostat is the gauge probe on, and which side is the fan probe?  I'm just trying to get a good idea in my head of how you have it all set up.

 

A couple simple things come to mind.   Are your fans blowing in the right direction?   Both of them?   What happens if you run your switched fan  when the engine is cold.  Does the engine get cooler?  Never warm up?   Stabilize at 180?  

 

Edited by HuD 91gt

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1 hour ago, HuD 91gt said:

Do you have any of the bypasses blocked?    Which side of the thermostat is the gauge probe on, and which side is the fan probe?  I'm just trying to get a good idea in my head of how you have it all set up.

 

A couple simple things come to mind.   Are your fans blowing in the right direction?   Both of them?   What happens if you run your switched fan  when the engine is cold.  Does the engine get cooler?  Never warm up?   Stabilize at 180?  

 

 

What do you mean by bypasses?  I'll attach a picture showing where the fan switch and gauge sender are tapped in. 

 

The fans are blowing in the right direction, the temperature controlled fan is a "puller" and the switched one is a "pusher", the idea being that in most conditions I'd want a puller fan but in traffic a pusher might help too.  I've not tried running the switch fan with the engine cold, mostly because it already takes so long to warm up.  I'm curious as to what your though process is here?  I'll give it a shot.

 

Here's a picture of how I have my thermostat housing set up. Note that this is not my picture or my engine, just a representation of how I have it set up. 

5a20415b54a5c_ScreenShot2017-11-30at9_31_57AM.thumb.png.6893cdf7e6fd5d13d40832960b79da4e.png

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My thought process with the bypass is that if you block it off the water pump is deadheaded until the thermostat is opened.  Apparently it takes a good amount of flow to get the water pump from cavitating.   The work around is to run another bypass (If not using the SU carb heater) and run it around the engine back into the system.   Secondly, you can drill, I believe a 1/4" hole or two in the thermostat which allows the water pump to flow some fluid throughout the system allowing proper warming of the engine.   If you have no fluid flow, your temp sensors(and thermostat)  won't be reading accurately either.  I am using the drilled out thermostat method.  Seems to work fine, although technically your engine will take slightly longer to warm up as you are allowing the system to recirculate through the radiator... slowly.

Take a look at this photo. If you remove the SU carb heater, your system has no flow while the thermostat is closed.

 

post-29130-050710200 1349202392.jpg

My reasoning for trying the fan switched on, is you should have minimal flow throughout the radiator when the thermostat is closed during warmup.   The fan running shouldn't change a thing, if you are running a bypass of some sort (Homemade or stock carb heater).   Just a way to find where the issue is.

Edited by HuD 91gt

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I really wasn't thinking too much. New Zed is on the money.

 

The thermostat should stay closed until it reaches the mechanical point where it opens at which you found at 170. That should mean the coolant in the engine should always be at 170 or so in theory or the thermostat wouldn't be open. The sender should sit right under the thermostat so when it until it opens it should be seeing 170, if it drops that means the thermostat is open, but still at 170.

 

Short of it sticking open when opened causing it to bypass the function of the thermostat, bypassing via another mechanism, or the sender going bad, hard to really imagine what is going on.

 

Interesting though, you have a pusher and a puller? That seems like it would take up a lot of room.

 

Nice little picture in there. Without the internal bypass of some sort the coolant would stagnate. Is your heater routed in that fashion? Or do you just have an inlet and an outlet in line?

Edited by seattlejester

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Are you over thinking the problem?

  1. Research the function of a thermostat.
  2. I see you are in the Bay area where it tends to  be cool. You haven't mentioned what the air temperature is when the water temp appears too cold.
  3. What are the temps on a 90 - 100 deg day?
  4. Perhaps you need to calibrate your temp gauge and sender by measuring actual water temperature with a digital thermometer (meat thermometer works). Place the probe between the fins close to where the return hose connects to the radiator.
  5. Could be that you just have an efficient cooling system!
Edited by Miles

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On 11/30/2017 at 11:00 AM, HuD 91gt said:

My thought process with the bypass is that if you block it off the water pump is deadheaded until the thermostat is opened.  Apparently it takes a good amount of flow to get the water pump from cavitating.   The work around is to run another bypass (If not using the SU carb heater) and run it around the engine back into the system.   Secondly, you can drill, I believe a 1/4" hole or two in the thermostat which allows the water pump to flow some fluid throughout the system allowing proper warming of the engine.   If you have no fluid flow, your temp sensors(and thermostat)  won't be reading accurately either.  I am using the drilled out thermostat method.  Seems to work fine, although technically your engine will take slightly longer to warm up as you are allowing the system to recirculate through the radiator... slowly.

Take a look at this photo. If you remove the SU carb heater, your system has no flow while the thermostat is closed.

 

post-29130-050710200 1349202392.jpg

My reasoning for trying the fan switched on, is you should have minimal flow throughout the radiator when the thermostat is closed during warmup.   The fan running shouldn't change a thing, if you are running a bypass of some sort (Homemade or stock carb heater).   Just a way to find where the issue is.

 

Ah okay this seems like something work looking into for sure.  I do not have any sort of bypass like that, or the su manifold so no water lines for it.  I'll have to decide if I want to plumb a bypass in or drill the thermostat.  I like the theoretical function of the bypass better but anything that adds to the possibility of coolant leaks (like more plumbing) is possibly worth avoiding. I'm guessing the little little hole that's already in the thermostat is not big enough? Also can you explain how the lack of bypass would make the engine run colder?  Or are you saying it just makes the gauge read lower? This really seems like it could potentially be the problem.  I did try warming the car up and driving it around today with the heater valve all the way closed, which lead to a small coolant leak that went away when I opened the valve back up. The coolant was leaking on the passenger side where my radiator hose meets the radiator (water pump inlet side).  I'm assuming the real problem was a clamp being loose, but maybe it is also indicative of the deadheading problem you're talking about.  Maybe the heater is being used as a bypass normally, causing it to never really get up to temperature since it's bypassing through the heater core?  

 

On 11/30/2017 at 11:05 AM, seattlejester said:

I really wasn't thinking too much. New Zed is on the money.

 

The thermostat should stay closed until it reaches the mechanical point where it opens at which you found at 170. That should mean the coolant in the engine should always be at 170 or so in theory or the thermostat wouldn't be open. The sender should sit right under the thermostat so when it until it opens it should be seeing 170, if it drops that means the thermostat is open, but still at 170.

 

Short of it sticking open when opened causing it to bypass the function of the thermostat, bypassing via another mechanism, or the sender going bad, hard to really imagine what is going on.

 

Interesting though, you have a pusher and a puller? That seems like it would take up a lot of room.

 

Nice little picture in there. Without the internal bypass of some sort the coolant would stagnate. Is your heater routed in that fashion? Or do you just have an inlet and an outlet in line?

 

Ok yes this is definitely pointing to the lack of bypass.  I hadn't even considered that I needed a bypass at all, it didn't even cross my mind.  Where the external bypass spits back out into the coolant line next to the alternator, I have one side of my heater core hooked up.  The other side is hooked up to the port near cylinder 6 on the head, it's what feeds the heater.  I think coolant is circulating around the block and not really moving to the thermostat housing at all really, since coolant is just moving through the heater normally possibly.  I wonder if my car is actually overheating most of the time but the hot coolant isn't accumulating at the thermostat housing so it doesn't read hot on the gauge.  And yes I have both, currently they're staggered so that one of them is pulling from the left side of the rad while the other is pushing on the right.  I think it would be better if I made them stacked on top of each other, and better still if I added a shroud.  I'll have to make a simple shroud up. Maybe that will even improve warming up since it will also act as a bit of an airflow block when the fan isn't on.  

 

On 11/30/2017 at 2:09 PM, Miles said:

Are you over thinking the problem?

  1. Research the function of a thermostat.
  2. I see you are in the Bay area where it tends to  be cool. You haven't mentioned what the air temperature is when the water temp appears too cold.
  3. What are the temps on a 90 - 100 deg day?
  4. Perhaps you need to calibrate your temp gauge and sender by measuring actual water temperature with a digital thermometer (meat thermometer works). Place the probe between the fins close to where the return hose connects to the radiator.
  5. Could be that you just have an efficient cooling system!

 

1. I have, sorry if the way I explain things makes it sound like I don't understand

2. The temperatures have been cold in 100 degree weather, and 40 degree weather.  On hot days in the summer it would definitely heat up a lot faster and would run a little warmer but overheat more easily.  

3. Maybe 165, usually closer to 150-160

4. That's not a bad idea, I'll give that a shot!

5. I'm definitely feeling confident in the radiator's ability to cool.  I think the fans need some tweaking and I need to figure out the bypass thing. 

 

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I can’t explain why the engine may run cooler. My only guess is a lack of calibration with your gauges. You have two thermostats, drill one out and see what happens, then go onto the next issue.

 

 

From what you explained, and looking at the diagrams I do believe your heater core is definetely acting as a bypass when open. Unfortunetely your thermostat isnt getting any flow, and without flow a complete lack of hot fluid passing by.

Edited by HuD 91gt

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6 hours ago, luseboy said:

I did try warming the car up and driving it around today with the heater valve all the way closed, which lead to a small coolant leak that went away when I opened the valve back up. The coolant was leaking on the passenger side where my radiator hose meets the radiator (water pump inlet side).  I'm assuming the real problem was a clamp being loose, but maybe it is also indicative of the deadheading problem you're talking about.  Maybe the heater is being used as a bypass normally, causing it to never really get up to temperature since it's bypassing through the heater core?  

 

 

Looks like you might be overthinking some things and underthinking others.  Close the heater valve and run with it closed, and determine what happens.  It's very important.  It might not be the source of your problem but you need to know.  

Edited by NewZed

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On 12/3/2017 at 6:29 AM, HuD 91gt said:

I can’t explain why the engine may run cooler. My only guess is a lack of calibration with your gauges. You have two thermostats, drill one out and see what happens, then go onto the next issue.

 

 

From what you explained, and looking at the diagrams I do believe your heater core is definetely acting as a bypass when open. Unfortunetely your thermostat isnt getting any flow, and without flow a complete lack of hot fluid passing by.

 

Ok so I cut the little brass nipple valve off and drilled a 7/32" hole in the (cheaper) thermostat today to test out the bypass problem.  When I pulled out the thermostat I looked at the coolant sender and realized that it's actually on 2 adapters: a 1/4 BSPT to 1/4 NPT, then a 1/4 NPT to 1/8 NPT adapter.  I'm not sure what I was thinking, but there's definitely the potential that an air bubble is staying put within the adapter set up.  At any rate, drilling out the thermostat seemed to help a lot in traffic, where it would creep up to 205-210 before it was drilled out, it now stays closer to 180 for longer but eventually starts to creep up to maybe 200 or so.  Also it will now get up to 180F without sitting in traffic, and will stay around 180F while going less than 25-30mph.  Once it gets going 35 or faster the temps drop back down to 150 on the gauge.  I then closed the heater valve, and noticed it did not start leaking coolant again (probably because I pushed the hose on further and tightened the clamp more, but still).  With the heater valve closed it did seem to heat up a little faster but still would run at 155-160 above 25-30mph.  On the highway it even got down to 150.  So then I put a piece of cardboard over half of the radiator and with the heater valve closed and have the rad blocked it ran at 165 on the highway.  I'm thinking maybe the hole is too big and also that it's probably not fully bled, even though I ran it with the cap off, the right front wheel on a ramp, and raced the engine a few times to get a good amount of air out.  I also think that I need to make a fan shroud and either see if I can fit the pusher fan as a second puller, use them as the bread in a radiator sandwich, or maybe get a bigger puller fan.  I'm also going to make a bypass above the intake manifold, and use the current 1/4 NPT port for it, and drill and tap an 1/8 NPT port for the gauge sender so it can work properly and not trap air.  Any idea what size tubing I should get for the bypass?  I'm planning on making it out of hardline if I can.  I'm wondering if I can get away with aluminum for this if I can insulate it from the block with rubber?  The rad is aluminum so galvanic corrosion would already be an issue.  I don't think my flaring tool or hands can handle stainless of a bigger size. 

 

On 12/3/2017 at 10:27 AM, NewZed said:

 

Looks like you might be overthinking some things and underthinking others.  Close the heater valve and run with it closed, and determine what happens.  It's very important.  It might not be the source of your problem but you need to know.  

 

Is there anything in particular that I'm under or over thinking?  Anyways read above for the heater valve.  It seemed to make some difference with warming up but once the car is driving it doesn't make a huge difference.  Of course this is only after I drilled out the thermostat, I should've tried it before I did that but didn't have time to.  When I closed it the first time and it leaked I was on my way to a friends house and didn't want to mess with it right then.  

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Have you set up the calibration of your aftermarket gauges?


I'd assume aluminum would be fine, i'd try and find out what the stock line size is on a 280z.

 

I would run your heater core the same way as the factory did it.   The water will flow the path of least resistance.   Make sure the flow with the heater valve open or closed will circulate through the cylinder head/block, flow by your thermostat and associated gauges before it has the chance to use the bypass or the radiator.

Think it through. 

Edited by HuD 91gt

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1 hour ago, HuD 91gt said:

Have you set up the calibration of your aftermarket gauges?


I'd assume aluminum would be fine, i'd try and find out what the stock line size is on a 280z.

 

I would run your heater core the same way as the factory did it.   The water will flow the path of least resistance.   Make sure the flow with the heater valve open or closed will circulate through the cylinder head/block, flow by your thermostat and associated gauges before it has the chance to use the bypass or the radiator.

Think it through. 

 

I'm not sure that there's a way to calibrate the autometer gauges, but I'm looking into it.  I did buy an autometer fuel gauge that was no good, so maybe this one isn't any good either. It seems to be reading the same temperature as the fan switch though, as the fan kicks on and off at the right points compared to the gauge.  Of course this is no calibration by any means but at least an indication in that direction.  I will look into that further.  

 

If I use aluminum I'll make sure and insulate it from the engine.  

 

The heater core is plumbed the same way as the factory did it as far as I can tell.  I'll triple check everything when I plumb in the bypass.  

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The thermostat stays closed until the coolant in the engine reaches desired operating temperature.  But your engine isn't heating heat up properly on the road, it just stays cold.  And you live in the Bay area.  It has to be producing enough heat to reach thermostat opening temperature.

 

The radiator removes enough heat to keep the thermostat at the point of opening and closing, if enough air is flowing through it.  But your engine goes above the thermostat set point eventually, in traffic.  Seems like your fans aren't moving enough air.  And running one pusher and one puller is odd.  Maybe remove one, it's probably blocking or screwing up the other.  Even better, remove both.  Besides that, you haven't said if you're actually switching the "traffic" fan on in traffic.  But you really shouldn't need it anyway.  You've over-engineered, for a problem that doesn't exist.

 

Those are two big clues, the staying cold on the road, and overheating while stopped.   You have a plain old L28 and with stock parts in good condition shouldn't be having any problems at all.  Focus on the basics.  Maybe get rid of the electric fans and go back to what has worked, and still works, for millions of cars.  Mechanical fans.  Then you can put a stock temperature sender in and get rid of the Autometer gauge problem.

 

Once you make it work the way it was intended to, you can put those parts back one at a time.

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So obviously I wasn't satisfied with the drilled thermostat set up, and decided to make an external bypass.  I was able to get 3/8 copper hardline locally by the foot ($5 a foot), as well as a tee that has two 5/8" hose barbs and one 3/8" hose barb.  Unfortunately, I can only find the tee in plastic but I wanted to see if the lack of an external bypass was actually the issue so I went with that for now. I pulled my thermostat housing off and took the temperature sending unit out of the adapter.  While it was out I used some boiling water and a digital thermostat to test my gauge and sending unit.  It's not dead on with the digital thermometer but pretty damn close.  It's not like the gauge has a fine scale or anything anyways.  I drilled and tapped a new 1/8 NPT hole next to the factory 1/4 BSPT hole in the thermostat housing, and screwed my sending unit in.  Unfortunately, I didn't take into account the shape of the thermostat housing and how that effects how far the Autometer sending unit goes into the housing (close to an inch, surprisingly far), and when I test fit the thermostat it hit the sending unit.  So then I drilled and tapped another 1/8" NPT hole in the bottom of the thermostat housing almost pointing into the cylinder head.  Now the thermostat would sit right and the sending unit was properly probing the coolant, and in the direct flow of coolant as well.  Then I cleaned the housing really well with soap and water and a brush to get all the metal shavings out and put it back on the engine.  I then spent some time bending the copper tubing into the right shape and getting it as flat as I could otherwise and put some little halfway done bubble flares on each end. I put a short section of 3/8" radiator overflow hose between the hardline and the tee with the heater core exit hose, with fuel injection clamps holding them on since I had some extras anyways.  I put a 1/8 NPT plug in the hole I drilled that didn't work. It didn't get super tight before it started to sink into the housing so I had to take the housing back off and re-drill and tap the hole to 1/4 NPT.  When I initially tapped it to 1/8 NPT I was on the phone with my dad and I wasn't paying attention and tapped it too far.  After cleaning and reinstalling the housing again, I bled the system and went for a drive.  It stayed right at 180F almost the whole time.  I put the heater on full blast and it stayed at 180F, even at 45mph for an extended amount of time.  It seems to run better too, which is a plus.  However, it does still creep up in traffic to 205 or so.  It also got up to maybe 200 on the freeway when I was romping on it a bit.  Cruising on the freeway though it fell back down to 180 and stayed there.  Plan is to build a shroud and maybe replace my current puller fan with a bigger and stronger puller fan as well if that's not enough.  I don't want to run a mechanical fan and shouldn't have to.  Also I suspect that the cooling system is not bled all the way, I'm gonna buy one of those spill-free funnels and spend more time bleeding it.  Oh, and I'm gonna get rid of the scary plastic tee that I know will break when I'm in the middle of nowhere leaving me with a significant coolant leak.  I can't seem to find it in another material but I just need to look harder.  I mostly wanted to update this in case someone else is dealing with the same thing and comes across this thread, I hate when I'm trying to figure something out and I find old posts where someone is dealing with the same problem but doesn't update how they fixed it.  Moral of the story: don't deadhead your water pump.  

Edited by luseboy

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