Cooling issue from hell

[Z3P0]

Hello everyone. I would just like to say thanks for even looking at this post. This is my first post and I'm not even sure if it's going to the right place haha. But I would appreciate some feedback if you're reading this, thank you.

 

So I've been workin on this car for about 4 years now. I know the insides and outs of the motor since I've built it. But I'm running into this insane cooling issue.

 

This is a Datsun 280z 1978, late 77. Running a stock bottom block l28. With an N47 top end from an 83 280zxturbo. It is NA right now. With some performance mods. Recent ac delete and upgraded suspension.

 

Once I was finished putting in suspension. I've done a complete overhaul of the cooling system since I've replaced my radiator.

 

New radiator (obviously) mishimoto all aluminum. New water pump, oem thermostat 180, new oem fan, new silicone upper and lower hoses, coolant flush, also some water wetter in there, did a coolant bled the system, brand new thermal fan clutch. This thermostat housing is off of a 280zx but the connections are the same just routed in different areas. I checked them to make sure they're working. I did not do any electrical tests, just some physical readings and made sure they were connected.

 

But the temp on the temp gauge reads too high for my liking. Looks like it's reading about 200-210 and my fan clutch is not kicking on. At start up it does but the coil doesn't hold up to help the fan pull air. This happens at idle. While I drive at highway or even regular speeds the temp goes dramatically down and stays at regular about halfway. But when the engine does overheat it stays at the temperature stated above. That tells me that my thermostat is working but it still over heats. I need help.

 

Before all this happened the engine did overheat before and I've been through 5 radiators and ran great. But this overheating issue is killing me since here in so cal it can get up to 110 degrees outside during the summer. So I'm just wondering what could be the problem.

 

Sensor issues?

Better bleeding of system?

Simple fan shroud?

 

If you need any extra info from me I would greatly appreciate that. Thanks!

 

~Henry

 

 

[Stanley]

Fan shroud. MSA carbon fiber works good but 2-piece would be handier. Maybe oil cooler for Palmdale. Nice cam cover. Is that powder coat ?

[siteunseen]

Have you put an actual thermometer in the radiator and let it idle until the thermostat opens?  My 240 needle sets on the right leg of the M in TEMP on the gauge.  I thought it was running hot too so i put a digital meat thermometer in and it runs at 173F sitting in my garage with no air flowing.  So long story short, my gauge is flaky and my temp is fine.

EDIT 176F with no airflow

Edited June 27, 2017 by siteunseen

[240260280]

What is timing at idle and at 3000rpm?

 

What head gasket did you use?

[Zed Head]

 

28 minutes ago, Z3P0 said:

the temp on the temp gauge reads too high for my liking. Looks like it's reading about 200-210 and my fan clutch is not kicking on. At start up it does but the coil doesn't hold up to help the fan pull air. This happens at idle. While I drive at highway or even regular speeds the temp goes dramatically down and stays at regular about halfway. But when the engine does overheat it stays at the temperature stated above. That tells me that my thermostat is working but it still over heats. I need help

I'd go with a shroud also.  If the car is lowered and/or has an air dam in front the fan might not be pulling air through the radiator, just spinning it around behind it.  Nissan built those shrouds for cars with AC because the fans can only move so much air without them.

You might also go back to a stock radiator.  Your engine is mild and doesn't really need what you have.  I have an OReilly cheapo radiator and a shroud and I have zero cooling problems even on the hottest days.

By the way, N47 is a stock 77-78 280Z head, not ZX Turbo.  You have a plain old 77-78 NA engine at this point.  Should be easy to cool.

 

Edited June 27, 2017 by Zed Head

[Pop's Z]

Just being nit picky, but the cylinder head from an '83 turbo car would be a P 90 and would require much modification to work on a flat top piston setup...not enough compression ratio. The N 47 head is from an non-turbo. +1 on the putting a thermometer in the radiator. These old gauges are notoriously inaccurate,

Cheers, Mike

[Zed Head]

35 minutes ago, Z3P0 said:

Before all this happened the engine did overheat before and I've been through 5 radiators and ran great. But this overheating issue is killing me since here in so cal it can get up to 110 degrees outside during the summer. So I'm just wondering what could be the problem.

2-4-6 Blue brings up a good point about the head gasket and the timing.  Could be that you really have a blown head gasket causing your problems.

[Zed Head]

3 minutes ago, Pop's Z said:

Just being nit picky, but the cylinder head from an '83 turbo car would be a P 90 and would require much modification to work on a flat top piston setup...not enough compression ratio. The N 47 head is from an non-turbo. +1 on the putting a thermometer in the radiator. These old gauges are notoriously inaccurate,

Cheers, Mike

There was a guy a few years ago who put a P90 on dished pistons just so that he could sell the car.  We told him about the CR but he did it anyway.  Still wondering who ended up with that car.

[siteunseen]

I think I've read some head gaskets block one of the coolant passages on certain head swaps?  If it's an N42 block and N47 head should be good to go but an F54 with an N47 maybe not?

Maybe this is what I read and it has the '83 turbo head, P90A

http://www.zcar.com/forum/10-70-83-tech-discussion-forum/120833-head-gasket-holes-don-t-match.html

Edited June 27, 2017 by siteunseen

[Reptoid Overlords]

Same thing happens to my ZX, gauge reads a touch high, but meat thermometer produces numbers within spec. When I first got it, it ran way hot. I decided to put the fan assembly from my parts car on and the temp went down in all conditions. One thing I noticed after switching fans was an audible fan noise once temp was reached that wasn't there with the original one. Do the early cars make that same noise when the fan is engaged?

[siteunseen]

1 minute ago, Reptoid Overlords said:

Same thing happens to my ZX, gauge reads a touch high, but meat thermometer produces numbers within spec. When I first got it, it ran way hot. I decided to put the fan assembly from my parts car on and the temp went down in all conditions. One thing I noticed after switching fans was an audible fan noise once temp was reached that wasn't there with the original one. Do the early cars make that same noise when the fan is engaged?

That's the fan clutch coming in and out.

[siteunseen]

Don't get mad, you've built a nice engine bay so this stupid but Nissan thermostats make a big difference and the spring goes down.