Mongo

This is a coolant temperature sender. I'd like to know where abouts it goes on the 944. After basically overhauling my entire cooling system this weekend I'm reading hot and my gauge is spastic, showing a drop from 3/4 to 1/4 operating temperature whenever I blip the throttle. It can mean that either the temperature sensor is bad or this cooling sender. I wouldn't mind replacing both to get a better reading for the computer's purpose.

Here's a picture and part number.

928-606-201-01

Mighty Shilling

Still sounds like an air bubble... did you bleed it the best you could? heater valve open?

Mongo

eh it boiled over on me again. Engine temperature went just about into red, and I smelled coolant. Then dropped down below half when i took off from the stop light.

And, check this out. We did a compression test right after. I pulled 145 on cylinders 2-4. Cylinder 1 came in at 180 psi because there was presence of oil on the crown AKA a valve guide.

Anyways, we have now proven that the head gasket is ruled out with the compression test. after the boil over (yet again) and taking a drive with another Rennlister. We noticed the car still had the same amount of power before. Did the same symptoms, but never boiled over this next drive around.

Very Odd.

However, we noticed that at 3/4 temperature the fan didn't come on full speed. When I blipped the throttle again, temperature went to 1/4 and the fans came on full blast immediately! Sensors are screwed.

BTW, I'm making an appointment to do an engine flush just in case of blockage that may be causing it.

Mighty Shilling

Hrm... that's no good. you did replace the fan switch? I'd start checking wiring.

As for that sensor, I'm not 100% sure, but it may be the one next to cyl.1 under the intake J-boot and intake manifold... has a blue clip on the wiring harness...

I dunno what else to suggest... You can flush it yourself... fill it up with water, dump it. fill it, run it, dump it. over and over again for about 5 times. works pretty well...

did you check the coolant tank and cap like Joe recommended?

Jfrahm

A leakdown test might show a little headgasket leak, I do not think the compression test will. If you have a bad headgasket it's not a big leak.
The other issues might be a poor engine ground and an air bubble in the cooling system.

-Joel.

aribop

That's the temp sensor for the gauge. It goes next to cylinder #2 and has two seperate wires that plug into it.
The blue clip sender is for the DME and has a plug like an injector uses. It sits beside this one you have pictured.

89magic98

Did you use an 80 degree thermostat?

What was the degree rating of the thermostat you removed?

The folks at Black Forest changed my thermostat with a 77 degree one many moons ago, and I noticed a difference in operating range when I switched to an 80 degree one - I wound up putting a 77 degree one back in.

Mongo

yes. Regardless though I'm running an 85/92 fan switch with an 80 thermostat. Remember this car boiled over with a 71 degree Celsius thermostat. This is not the case since they are both openeing. It should not get that hot. It would stay at half but not go to 3/4s. This is really confusing. I really think one of those sensors is faulty.

I used a pyrometer on the radiator hoses when hot and came up with 171 on the top and 164 on the bottom. This is not a hot operating range for this coolant in the car. Has to be a sensor

Mongo

ok i found the temp sensors and my coolant a little lower because of the boil over today.

There are no coolant leaks other than the overflow valve. There has to be some sort of electrical issue causing the fans to malfunction and coolant to boil over because the fans didn't come on full speed when it got hot today.

Joel all spark plugs were clean too when we did the compression test. None of them showed coolant traces such as wetness or even a steam cleaning.

SoCal Driver

Could be an electrical issue. I think that some where there is a very small leak that lowers the coolent in the engine just enough to cause an air bubble. Then you get the run away over heating. Doesn't take much to lower the coolent in the engine and the top of the radiator where the fan switch is.

Might think about getting the UV dye for the coolent and searching with a UV light at night.

Just a thought; your thermostat may be sticking. Even new ones will stick.

Mongo

nope. It's opening alright Socal. But, I definitely haven't ruled out the possiblity of an impeller failure on this rebuilt water pump. Time to call my buddy who put the rebuilt in. It's time to start there, seeing that everything else on the cooling system is brand new

Mongo

Ladies and Gentlemen we have found a cure!

colder thermostat to match colder fan switch!! 80C is too hot for an 85/92 fan switch! I had to use a 71C

sharky47

Well, I'm glad that is taken care of......

Mongo

yea you have no idea...

89magic98

HAHA, I knew I was on the right track. They (fan switch and thermostat) have to be matched sets in order for the system to work properly.

But you didn't say that you had switched the fan switch or thermostat before the problem started.

I'm wondering where you found a 71C. Took me a long time to find a 77C on the internet.