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Hey Guys,


I have battling this overheating issue. My car is a 1972 240z with an l28et, which is pretty much all stock.

I have a new 3 row radiator from ebay, new oil cooler from ebay. The water pump is working. The motor has just been built and assembled. I show good compression and tested my thermostat to make sure that it opens. I have the heater core hooked in so that the water will go to the back of the motor as well.


As soon as I get to operating temp around180 it climbs slowly in city like driving. I am not pounding the car. It only has 150 miles on it. I am just cruising with some small pulls. When sitting at lights it starts to climb. I have flushed the system 3 times last night and saw some stuff come out but nothing crazy.


Any suggestions?

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1 hour ago, supershanesta said:

I have two electric fans running. Always on. Still having issue. Intercooler is blocking but its not that huge.


Blades spinning doesn't mean air flowing.  Take some time to study/understand heat flow and how the radiator radiates and you'll see why low air flow is the likely cause.  It's called a "radiator" because it disperses/radiates heat in to the air around it.  Ideally the heated air leaves.  With the heat it absorbed.  If it doesn't leave fast enough it gets hot and won't absorb as much heat.  There's a time element involved.  At speed, on the freeway for example, more air flows through the radiator and the fans are useless.


The hot air has to get out of the engine bay also.

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Assuming, and that is a big big assumption on our part without more information, that the cooling system is working, I agree with NewZed. Having the fans on all the time may actually be a problem. At low speed not much of an issue, but depending on design and threshold they can be a restriction if you are trying to spin them at a motor rate and the air is trying to flow faster around them. 


Are you running a shroud? Similar vane with having the fans on all the time, not running a shroud the air is going to want to flow around the radiator or through the side of it rather than through the center of the core. 


Have a picture of the system you can share with us? Hard to tell how well a system is put together without visual aids.


I have a 2 row champion/ebay radiator with twin electric fans on my 2jz na-t and it has driven through 1/2 an hour of traffic with maybe a 2-3 degree rise from 180.



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I had a similar problem with my dual electric fan set-up driving at lower speed around town.  The fans were rated at a good airflow, but it turns out this was at free flow (no back pressure).  The fan curve for these low cost fans showed that the flow rate dropped off dramatically with just a little back pressure.  My 240z has a lot of back pressure in the engine compartment (poor airflow out).  I replaced electric fan with a more powerful Spal fan that has a better fan curve.  It solved my problem.

Edited by scott
Misspelled spal
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Hey Guy,


Sorry I have been waiting for an Altima fan setup.


They are cheap push fans. 3 core ebay radiator.




I do not have a shroud. This altima fan setup does. I also am going to wire it to the megasquirt to turn on properly.

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You say the fan you are running currently is a push fan? If it's mounted on the backside of the radiator, as the picture shows, and is setup in a push orientation I would put my money on that being the problem. If it's on the back of the radiator like that, it wants to be a puller.



Pullers, by design, are more efficient.


If that is not the case, forgive my ignorance.

Edited by OldAndyAndTheSea
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I bought a 3000 CFM electric fan from eBay years ago for maybe $30 and it really helps sitting in 110 degree weather at a stoplight.  I do not have a shroud either so maybe your fans are not strong enough or there isn't enough electrical power to really power them up?  When mine come on, you can really hear them and the engine cools down pretty fast.


Years ago I changed the radiator to my Nissan Maxima and I immediately had a problem with overheating so the fix was to let the car idle with the cap off to get the bubbles out.  The radiator fluid would burp a little and then I would just add more fluid.  Just an idea.


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Assuming that the system is well bled (I usually try and find a hill to make sure the radiator is above the thermostat, then burp the system, give it a few revs, a sealed funnel to cap works really well as it will let air escape and immediately fill the void with coolant under column pressure). 


I'd say then it is a combo of air pushing around or past the radiator and your fans being on all the time.


You can see if that is the problem by blocking all the holes around the radiator that aren't being used with aluminum tape and building a make shift block off between the front spoiler and the radiator support on the bottom and the radiator support and the hood on the top. Once you get onto a nice open freeway, turn your fans off and see if the engine gets hot. If it still does then you have some other type of problem like coolant flow, slipping belt, etc. If it cools off then you just need more permanent shrouding around the radiator and the shrouds

Edited by seattlejester
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After putting in the Altima Fan things are going fine.


I had to cut a lot of it to fit as its wide and also to thick for the turbo piping I have at the top. It almost hits the radiator outlet to the water pump. I had to cut the radiator hose shorter so that It would move and successfully fit. My radiator is 25" across if I remember. I think the stock ones are 26".  It works like a dream. I have it hooked up to my megasquirt via a relay. It kicks on at 180 and cools down to 170 in seconds. My heating problem is all solved. If I was to do it again I would try a fan and shroud built for the car as this was more work than I wanted and I had to redo some turbo piping to get it to fit which cost $.


Shitty but Effective. If anyone is interested its from a 2001 nissan altima.


I will do more testing and get back to you guys as I have a new 160 thermostat (i drilled holes in my last one), but not seeing overheating at all.


Thanks everyone.





Edited by supershanesta
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They are set to high. I cut the connectors off. 2 blacks 2 blues for each connector. Using both they go on high. I cut about a half inch off the back of the shroud to clear my piping and water outlet. Note that my radiator is thicker than stock.Pully is in between both fans with no issue. I have the one with 3 belt options so it sticks out. With an ac compressor or other belts  it might be close i dont know. I can take pictures after this weekend of specific areas of concern if your interested.

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