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Running cool (maybe?)


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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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Glad to hear some of the problems are sorted.    Unpowered Windmilling propellers in aircraft cause a huge amount of drag.  Opposing fans, in my head would be causing quite a bit of turbulence. I wouldn’t be surprised if this is causing a lack of airflow through your radiator. My sugguestion now is removing one of the two fans (I’d remove the pusher) and running the system as is. Of course a shrouded system doesn’t hurt.  If your fan isn’t covering most of the radiator I’d say a shroud is required.

 

Keep us updated.

 

I use to have my fans on a 5 terminal relay. The thermo switch would turn on the fans at the appopriate time, and I also had a switch inside the cabin which would turn them on as required.  Using this method you could scrap your second fan. Lighter, less complex and you have a backup fan on the shelf when the first kicks the bucket.

Edited by HuD 91gt
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