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Overheating


Quandary

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So the L26 has always run hot.  Usually sat at around 80 degrees in hot weather.  I've done everything I can think of to ensure it wouldn't get any worse and already spent a lot on new radiator, core, fan, etc.  It's not losing any coolant.  The temp in the lower end of the system is around 63 degrees.  Yet lately the engine temp just blows out to 100+!  I can't figure it out and I just won't drive it with a feeling that I'm killing it.

 

I have done everything to the extent of my knowledge of the cooling system.  I've taken it to two different people and they've basically looked into what I've already done and told me it's an old car and it will run hot.  I am absolutely stuck and started thinking about probably irrelevant things related to engine temp like gearbox conversion, upgrading to the L28, front air dam, etc.

 

Anyone got any ideas?

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I've always used genuine Nissan thermostats without any issues. I recently got to the bottom of my cooling issues. Was the radiator at fault but after a very thorough strip and cleanout, it's all good. Are there any kinked hoses or factory hoses blocked off in a strange way?

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If you have flushed you radiator (or replaced it and have a genuiane thermostat (rarely go faulty) and have replaced the water pump ............Check your temp gauge..............is it actually running at 103 deg or is that what your gauge is reading, I have seen temp gauges go faulty (my old 240 race car did it).

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I'm not sure that it is faulty because it fluctuates as I would expect it to depending on the revs/conditions and time of day.  As for the brand (its not a genuine Nissan thermo) I'll have to find out.  The pump is new.  The temps were read with a sensor (needed to check the temp of the coolant after being cooled) and by the gauge, but I didn't actually check for the highest temp with the thermo.  I will have to do that, cos I suspect it will be higher than what the gauge indicates.

 

Anyway its too upsetting to think about.  I'm inclined to garage it until I have time/can afford spending on it.  I've spent 7 or 8 years spending money on the same shit all the time and all I want is a box conversion and new paint. ::)

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The shroud is there and hood is vented.  I've kept the vented bonnet for the appearance if anything.  The fan is the original multi blade, the pump from a VL.

 

Not thought about an electric fan.  I heard some criticisms of these on other cars, Morgans and the Escort block type.  Also I would not be keen on attaching kits cos those I've seen use plastic ties that go through the radiator.  Anyone got these on their Z?

 

Over the weekend I'm going to pull out the A/C and also see what it runs at without the thermostat.

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In that case I imagine your heating problem is quite normal. Not saying it's ok, just that it would be normal for a datsun, especially with air-con (you will have the aircon radiator thing in front of you normal radiator meaning less cool air going onto you radiator).

 

A mechanical fan obviously pushes more air when the engine is revving higher. So if you are idling in traffic in Brisbane on a hot day, I would expect the engine to work up to those temps. If you put on an electric fan, it only kicks in when it gets to a certain temp and will keep working even in you are at a standstill. They don't seem to push as much air as the mechanical fan at speed (but generally the air moving through the engine bay at 60-100kph is enough).

 

I would either recommend a push/pull setup or at the minimum 2 pull fans with a decent shroud. I made up a metal bracket that bolts up to the radiator, you can see my thread here when I was looking into electric fans http://www.viczcar.com/forum/index.php/topic,4003.msg34631.html#msg34631.

 

260coupe i think it was, said to just go with cheap ebay fans rather than the expensive (but good) davies craig type. Been on my car for about a year and no problem yet. If you have excess money I would say just go for Davies Craig, but yeah the cheap ones seem fine to me.

 

I'm not running a shroud at the moment and generally the temps are fine. I would like to add a shroud though so the fans don't have to work as hard/often. Just have to get around to fiber glassing one up.

 

I would still recommend that HPC on the exhaust manifold as well. Looks good and I think in your case you need to minimise as much heat as you can.

 

Just my 2 cents, I'm in no way an expert :S

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If you do have an AC condensor in front of your radiator, you should also have an electric fan blowing through the coil of the AC whenever the AC is on. The stock 260Z fan should be fine on it's own with the shroud. I'd replace the thermostat if the temp fluctuates too much.

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Argh, I lost my post.

 

Firstly for the sake of $15 I would replace the thermostat, or at least test it.

 

I don't agree that it is necessary for a 30 year old datto to run hot all the time, even in a Brisbane summer.

I've got jetcoated headers, non-vented bonnet and a non-shrouded fan. It doesn't run hot. Bonnet vents will be helping a lot more that ceramic coating the exhaust manifold.

 

Is it possible that you are running lean? Do you get a lot of overflow coming out through the radiator cap/drain?

 

 

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I don't think its acceptable or necessary that it's overheating, I just think its understandable that a car that is known for running hot from the dealer when it was new, would run hot after 30 years of driving. I'm not saying it can't or shouldn't be fixed .

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And I also agree that for $15 you should replace the thermostat.

 

I also have a sinlge, unshrouded electric fan and non coated headers on my daily driver and that doesn't overheat. I've personally never really had a problem with the overheating (except for once when the thermostat died). But in some cases people have had to resort to other aftermarket measures to fix overheating problems.

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  • 3 weeks later...

Mate,

 

i have had this problem on two different cars for two different reasons.

 

First car was an easy fix, just remove the thermostat...its so obvious that it makes you cry in frustration...this was mentioned earlier.

 

 

Second one is way trickier. It happend to my last Z so hold on here  it is.......

 

Car ran hot and I couldn't work it out....then by chance due to a leaky water pump I stumbled across the problem.

 

The aluminium timing cover (the one at the front not the rocker cover) had developed a hole between two water jackets that lay inside the water pump.

 

So effectively when the pump pumped it heart out all it did was either bypass the engine/radiator or it made it so inefficient that it didint do its job.

 

If its not a hole its a blockage in one of the cores.

 

good luck.

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Much thanks to all.  I've taken advice from everyone here thus far.  Still a work in progress mostly due to my time constraints and that I only ever see my Z on the weekends. :'(

 

The A/C unit is out.  And currently testing a few different brand thermostats.  It's down to around 90 degrees.  My aim is lower than this but I'm pleased with the difference already.

 

Other things on my to do list is to remove that A/C radiator thing and other minor A/C components.  Unfortunately don't have the gear to even make a simple bracket for an electric fan and have yet to find someone that will do this.  Lastly I'll look into the coating for the exhaust header, as am hoping for a L28 swap.

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