Overheats

Re: Low Idle, Overheats - Suspect CHTS wiring (no ECU codes)

Fuel temp sender needs to be working.....

Sounds like you MIGHT have an air bubble stuck in the system ( does the heater core get hot)?

Can you confirm ( using a laser thermometer ) the coolant temp??

Mike

Re: Low Idle, Overheats - Suspect CHTS wiring (no ECU codes)

I do not have a laser temp gun, but would definitely look into renting one (if Autozone, etc carry them).

I tried burping the coolant system by running the car, shutting it off, and then removing the rad cap. My heater does not work, but the rear hoses do get warm also.

Re: Low Idle, Overheats - Suspect CHTS wiring (no ECU codes)

Hmmmmm I think you still have air trapped in the heater core.... Laser guns are cheap and a great addition to your toolbox

Mike

Re: Low Idle, Overheats - Suspect CHTS wiring (no ECU codes)

if you are trusting the stock gage to tell you about overheat you are a really trusting soul.

Re: Low Idle, Overheats - Suspect CHTS wiring (no ECU codes)

I believe I fixed my low idle issue, though I'm not sure how (unplugged CHTS, retwisted the engine loom). I'm idling at 1000 RPMs in park now.

I found a coolant hose that was missing it's clamp screw. Fixed that. Still overheating (cool lower hose and radiator, hot upper hoses and upper radiator).

Re: Low Idle, Overheats - Suspect CHTS wiring (no ECU codes)

sounds like a water pump not pumping or a plugged radiator core or a bum thermostat.

Re: Low Idle, Overheats - Suspect CHTS wiring (no ECU codes)

When I tested the CHTS (as per EFEC-56), I found 0 resistance between 26 and 36 (as opposed to infinity). In other words, I failed the insulation test on the harness wires for terminals 26 and 36 leading to the ECU. All the other wires/tests passed.

Click to expand...

Oh well. More stuff to fix.

monkbonk said:

I believe I fixed my low idle issue, though I'm not sure how (unplugged CHTS, retwisted the engine loom). I'm idling at 1000 RPMs in park now.

Click to expand...

1000rpm is somewhat high if that is the idle when warm. Should be about 700rpm in D with no accessories on.
1000rpm in neutral is ok on a stone cold engine.
Does the idle speed increase when the lights or heater fan are turned on?

Z31's like having the front of the car raised when refilling and bleeding the cooling system.
Was the coolant bypass hose ever removed on this engine? I remember one Z31 I worked on that had the coolant bypass almost completely blocked with deposits.

Water pump, radiator cap and thermostat are all new.
Idle is 700 in D/R and 950/1000 in P/N
All coolant hoses have been removed prior to assembling the engine.

Updated 1st post.

The front of the radiator is not blocked with shopping bags or road kill?

lol, nopes

My bottom hose - the one leading to the thermostat is squeezeable (though it does have some pressure on it). I also noticed that the bottom heater core hose is squeezeable.

I've read that the thermostat opens at 180 degrees/water boils at 212 degrees.

During the times I've had it reading really hot, I've never seen the water boiling (reservoir). And, if I drive it a bit, the thermostat opens up (I think, as the lower hoses finally get hot/warm).

I've just recently tightened the waterpump/alternator belt as tight as it'd go. I think that alone has made some difference (I could feel water running through the upper hoses/cooling them off after I made the alteration).

So, I'm thinking that I need to run the car a bit with the tightened belt to see if that does anything, The belt's pretty taught and there's no more room for adjustment on the alternator tightening bracket (may need to replace my belt).

Ok.

Ran it. Still heats up towards past the halfway mark on the temp gauge. Once it gets to a certain point though, the temp gauge stops moving.

The lower hose does get warm at that point, so the thermostat opens.

I think my temperature sensor on my manifold is bad, or at least I want to think that. I've got a spare that I shall put on.. sometime.

Water boils at a higher temp with coolant... what percentage mix are you running?? What color is the coolant now?

Mike

Pure water.

It's not boiling. The color of my coolant/water is clear. Flushed the car three times.

Hmmmmmmm

Pure TAP water??

Maybe time to put some coolant in there...

Mike

I've actually read the opposite.

Water can take on more molecular energy, given it's ability to change forms (solid, liquid and gas). People in warmer climates tend to take on a heavier water mix versus antifreeze.

Coolant lowers the freezing point but does not do much for the boiling point.

Yes that's all true , BUT it also acts like a lubricant, raises the boiling point,and will be easier to see/smell if you have a pressure leak.
I wouldn't use straight tap water..... lots of minerals.

Mike

Ah, I see. I ordered an infared temp gun. I'm going to correlate whatever readings I get from it to that of my dash gauge to see if my sensor is accurate.

I'll have to get some antifreeze to mix in. Perhaps I should bypass the heater core or even the water switch?

AND I would get the nose up in the air as HIGH as I can to assist in burpin the baby!

Mike

I figured out why I wasn't getting interior heat. The PO did up some custom bypass stuff with the vacuum lines around the water switch.

I have also finally gotten my hands on a infrared temperature gun. My car's top radiator hose, at the highest temperature I've gotten it thusfar is 169 degrees Fahrenheit. At that time the lower radiator hose was reading 156 degrees F.

The radiator cap reads pretty close to the lower radiator hose temp