Temp sensor

[Alexb944]

So my temp always fluctuates between the second and third line like in this pic. Typically stays right where it is now.. this is after I tried to bleed it from the bleeder valve. Thoughts? Also with my heater on all the way I have no hot air unless I push the defrost button the air from hell comes through.

[Toran]

Have you tried replacing the temp sensor under the hood?

[thomasryan]

Does the system hold pressure?

[Alexb944]

I havent replaced the temp sensor yet, Im actually going to look for directions for that today. And I assume it holds pressure... partially because idk what that means... but I replaced the cap because the factory cap popped off and blew a hole in my resivour last summer... (how you ask? idk..)

[Toran]

Its very simple to replace but you got to get your hands on it first. Like most 944 thing you'll have to remove some parts to get to it.
Put some shop towels the sensor before getting your wrench on it because it will release coolant!

Here's what you'll be looking for somewhere underneath the the MAF I believe.
Also when I bleed the system I like to make sure the front end is up as high as possible so gravity can work with you getting ride of those air bubbles.

[Alexb944]

how difficult is the head gasket? I mean while im there, might as well right?

[Toran]

Not very difficult, just take your time.
Make sure you have a sharp blade to clean off the old gaskets so the new ones can be nicely seated.
If they haven't been replaced might as well since your going to be in there. Plus you will want to have the gaskets anyway just in case one or two of the old ones wants to be stubborn!

[peteb]

Hi,

This sensor is for the DME. It will not have a effect on the dash thermometer. There is a sensor next to it with two spade connectors. That is the sensor that drives the dash thermometer and the warning light.

Are you in traffic when the needle gets near the upper 2/3 line? Are your fans coming on? They should be. You could also very well have a thermostat that is opening late. It is a good sign that the temperature is not running away. Your car is hot, but, is not overheating.....


Peter

Originally Posted by Toran

Its very simple to replace but you got to get your hands on it first. Like most 944 thing you'll have to remove some parts to get to it.
Put some shop towels the sensor before getting your wrench on it because it will release coolant!

Here's what you'll be looking for somewhere underneath the the MAF I believe.
Also when I bleed the system I like to make sure the front end is up as high as possible so gravity can work with you getting ride of those air bubbles.

[Alexb944]

yeah both fans are usually running, and i just replaced the thermofan switch.. ive always assumed the thermostat was faulty since i had the timing belt and waterpump installed because i never had a temp problem before the waterpump went out and i replaced all of it.. but dang is it annoying now.

[peteb]

Hello,

You cannot rule out more that one thing being wrong with these old cars.

I'm thinking your new thermostat is opening closer to 95 degrees C rather than the 83C that it should be.

It could also be that your new thermostat is good, but, the old thermostat was too cold AND your dash thermometer is reading high. The thermostat that came with my 944 was a 15 year old 83C Porsche unit that was opening at 70C. I did some trouble shooting and figured out my dash thermometer was correct.

I would pick up a IR thermometer and check the temperatures of the upper radiator hose as the car warms up.

The heater is a puzzle. Heat on defrost indicates the climate control can open the water heat control valve, the engine thermostat is not completely open blocking the heater circuit, and the heater box flaps are moving to heat. The heater problem sounds like it may be a climate control issue. Did this problem just start with the pump work?

Peter

[Alexb944]

I never realized the heater not working because when the wp went bad it was in dead of winter, so i always had the defrost on. but the "overheating" started when the wp was replaced.

[peteb]

One more thought about the heater.....

If the car is truly as warm as the engine temperature gauge indicates AND the thermostat is working, you should not be getting "heat from hell" on defrost. The engine thermostat should cut off the water to the heater circuit at 90C when it is fully open.

This all points to some wrong with the thermostat or thermometer, rather that something bigger wrong with the engine.

Peter

[Alexb944]

dumb question... is thermostat the same as a thermometer?

[peteb]

By thermometer I was referring to the gauge on the dash. "Temperature gauge" would have been smarter and more consistent wording. Thermostat is the part in the water pump, of course.

Peter

[Alexb944]

yeah the thermostat is on the outer part of the waterpump, that has a annoying little clip on the inside... and okay i was just making sure i wasnt supposed to be looking for a thermometer.