Frustrated with Over Heating Problem 944 NA

[jeh1995]

I have a 1986 944 NA. Car has always run a bit hotter than 944's described on the web (1/2 gauge or a bit more). Recently it started running at the higher mark on the gauge (100C). Ambient temp is about 95F (south Mississippi). I have tried about everything; new radiator, new thermostat, new sender for gauge, gauge calibrated correctly with resistors, fans are running correctly with a new radiator switch, laser temp gun pointed at gauge sender shows about 92C. I have a radiator pressure tester and I've burped the engine several times (getting only coolant). Hoses are about 8 years old and don't seem brittle at all. I don't see any indication of a collapsing hose. Heater puts on good heat. What am I missing? According to people all over the web in Florida and California this car shouldn't have this kind of issue. So... I'm stuck and out of ideas. Looking for any and all suggestions.

[alan6272]

I have found on some vehicles that a head gasket can cause what you describe. A head gasket can leak some combustion gases into the coolant passages . A vehicle may run at normal temp in idle but once driven and under load it can cause the temps to run high. A poor water pump can cause this as well but you said the heater works fine so I would rule out water pump as this is what sends coolant to the heater core. There is a way to test if combustion gases are entering the radiator, with a die in a canister over the radiator opening. This is a specialized tool and die system that maybe your local radiator shop should have. Ask if they doo and if they can test this for you. Keep us posted.

[alan6272]

I just found that you can rent this tool from Autozone and advance, check your store.

[Grandad#3]

Did you match the Radiator Thermo Fan Switch with the Thermostat? They should be as close together temperature wise as possible. Some thermostats are not marked with the temperature number. I ran into this when I replaced mine and had to order a new one and specified what I required.

Cheers,
Larry

[1982_928]

Get some of the stuff from orielly's or autozone called water wetter (or something of that nature) Knocks off 20-30F. Ive used it many times, and it works wonders.

[mueller944s2]

I'm about 50 minutes away from you in Mandeville and mines having the same overheating problem, but I know I have a leak somewhere. Is the thermostat high or low temp?

[jeh1995]

I don't have any coolant leaks and I don't appear to be loosing any coolant. I don't see any bubbles or other indications of a head gasket leak.

My fan switch and thermostat are all "stock" (80C) so I think they match. I'll check that later. The fans pretty much turn on and off as they should.

I have a laser infrared temp gun. The temps read on that seem to match the gauge. If I shoot the area at the bleed it is about 90C, the area at the sender is hard to shoot but I think it is a bit hotter.

I'll research the Autozone tool. I'm pretty friendly with the local guys. Porsche isn't the only "odd" toy. I have an Early Bronco with a lot of not-Bronco parts too... I guess I'll try some water wetter. 30 degs... we'll see.

Any other ideas? I really appreciate the help! I'm out of ideas...

[alan6272]

A bad head gasket can be so slight that you may not see bubbles, I know this first hand. If the head gasket was bad enough to see bubbles, the motor would also misfire and smoke white out the tail pipe. Keep this in mind. If you go to youtube you can find videos of this problem good luck.

[StaceyAnthon]

have found on some vehicles that a head gasket can cause what you describe.

[jeh1995]

I'm going to try the block tester route to see if if can see hydrocarbons in the coolant. I sure don't want to simply repace the head gasket without some sort of confirmation. I don't have any other symptoms indicating a head gasket problem. I hope to have the time this coming weekend to do the test. I may even put some water wetter in just to see if that stuff does anything.

Thanks for all the suggestions.

[John_AZ]

When I put the new Pelican Wahler 80*C thermostat in my '87 the temp went to half up to 3/4.

Tested this a couple of weeks ago with new 80*C thermostat when I flushed and refilled coolant.

I took out the 80* thermostat and installed a new Wahler 71*C thermostat (which was same as the old temp thermostat in the car at the beginning when I started)

Temp stays at 1/3 to 1/2 with AC on at 100*+ ambient temps. (Same as before when I began the coolant flush and refill.)

Radiator fan relay/switch is 75*C

87 944 getting hot...

Also, are you using the correct thermostat in your updated WP?
Do you have the "new or old style" upgraded WP?
Thermostat - General Information, Testing, and Replacement

John

[jeh1995]

I have an old style water pump with the groove 4.5mm from the seal lip. The thermostat is an 80C, the fan switch is an 85C switch. I'm ordering the 71C thermostat and 75C fan switch. That would be a lot better than removing the head needlessly. Does Pelican have the 71C thermostat? I can't find it in their catelog...

[alan6272]

John, you would not have to remove the head needlessly, if you run the test for hydrocarbons and found non, you would be sure the head gasket is not to blame. However if there are hydrocarbons in your coolant than nothing you do to keep it cool is a waste, just talking from experience. Good luck.

[fennacf]

Are you running a quality thermostat? I had a similar issue with my car until I installed a Wahler thermostat with the appropriate spacer and seals.
Good Luck, Andrew

[jeh1995]

Update - still not fixed...

I ran a hydrocarbon test a couple of time with negative results, no color change. The head isn't leaking. I checked the blue fluid using CO2 from my breath... the system worked as advertised. Again- no head leak.

To make sure I didn't have any air in the cooling system I tried one of the vacuum based lead checkers/fillers. Pretty cool way to do business. The cooling system is full without any leaks and without any air in it.

Car still running at the 100C mark. On the highway it is steady there. Turning on the defroster make a lot of heat, but, doesn't lower the water temp at all.

I'm using a Wahler 80C thermostat and 85C fan switch. Fans are working properly, 2 speeds, on when they should be according to the gauge. I calibrated the gauge from the sender to the dask gauge using precision resistors... it is right.

Sometime next week I'll receive a 72C thermostat and 75C fan switch... we'll see. Thanks for all the help so far...

[VirginiaF1]

Originally Posted by jeh1995

Update - still not fixed...

I ran a hydrocarbon test a couple of time with negative results, no color change. The head isn't leaking. I checked the blue fluid using CO2 from my breath... the system worked as advertised. Again- no head leak.

To make sure I didn't have any air in the cooling system I tried one of the vacuum based lead checkers/fillers. Pretty cool way to do business. The cooling system is full without any leaks and without any air in it.

Got your pm, we look fwd to your lower stat and fan switch updates.
New Radiator is oem?

[dangerous]

I'm going to put my money on a flow problem in the area of the radiator. A lower temp thermostat and thermo fan switch certainly can't hurt, but I don't think they are going to solve your problem. If you're running hot at highway speed, you're fans are not going to help you at all (which makes the fan switch irrelevant). Unless there's a blockage in front of your radiator, you're getting all the air you need at highway speed.

if you have an A/C condenser (i.e. you haven't yanked out the a/c system) I would check to make sure this thing isn't full of debris and blocking your air flow. I'm not going to tell you to yank it out and lose your system charge....but you might be getting close to that point soon.

The other area of "flow" obviously is the coolant. If you're getting temp readings on both sides, your thermostat is probably opening. If you are going to be digging that thing out anyway, make sure you check it in a pot of water before you install it just to make sure. Another thermostat tip is to drill a 1/8" hole at the top of the flange when you install it. Helps with bleeding out air.

One more thing, since you'll be draining your system to swap your thermostat, it's a good time to pull that radiator out for another look. I know you said it was new, but you might run it down to a radiator shop and have them flow test it just to make sure there isn't something inside blocking the flow. Your symptoms sound a lot like blocked radiator flow to me (despite being new) so it might be time to look at some less common possibilities. Could be foreign matter (perhaps from shipping) packing peanuts, plastic, gunk or sludge from a hose, dead mouse, etc that found a nice spot to rest in your radiator.

[jeh1995]

FIXED! I had the chance to get under the car and taste antifreeze this weekend. I installed the 60C thermostat and a 75C fan switch. I agree completely that this problem seemed like a flow issue. So... I flushed the whole thing. While completely engaged (call that wet) I grabbed the original water pump to compare with what was installed. I actually have a NEW style pump installed and I was incorrectly using the thin gasket. This allows the thermostat to sit too close to the bottom of the housing and it won't open properly. With the correct (thick) gasket, 60C thermostat, and 75C fan switch it runs a bit under 1/2 (middle mark) on a humid hot as hell Mississippi day. I've been using a vacuum based system that "sucks" coolant in to the engine/system. I found that I still needed to burp the car after that... a pressure system works better... Hydrocarbon tool for head leaks - that is awesome. I have a number of play cars to the tools don't sit long...

Thanks for all the suggestions.

[John_AZ]

First, great news on the temp at 1/2 or less.

I need more explanation.

A 60*C thermostat? 60*C = 140F. That is really a cool temperature.

The "thick" 4.5mm thermostat gasket that covers the thermostat is only used with the NEW style pump with the 7mm distance.

The steel support washer is also used.

[jeh1995]

Opps - that was supposed to be 71C Thermostat. This get more and more interesting. The original WP (off the car) has the C Clip Groove about 2mm off the shoulder. This is pretty confusing, right? The installed WP has the groove at 4.5mm.

I installed the thermostat using the 4.5mm seal. I didn't install the shim washer. The C Clip looks like it is pretty tight against the seal. I am confused here a bit. I have the newer model WP and newer model thermostat. I used the 4.5mm seal. So... the washer pushes the thermostat against the shoulder to get a better seal? This is head hurting a bit!