Jump to content
HybridZ
luseboy

Running cool (maybe?)

Recommended Posts

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

Share this post


Link to post
Share on other sites
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.  

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites
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. 

Share this post


Link to post
Share on other sites
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.

Share this post


Link to post
Share on other sites
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.  

 

 

Share this post


Link to post
Share on other sites
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.

 

Share this post


Link to post
Share on other sites
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?  

 

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites
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? 

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites
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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites
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. 

 

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites
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

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...