dek944

Hi everyone. I know I am a newbie here and everything and this is my first post, but I am wondering if anyone can solve this problem. Here is the specs:
1986 Porsche 944 - manual - 84000 original miles

Here is the problem -
On typical driving the temperature gauge is steady at 1/4 on the scale.
When driving, sometimes more so in traffic, the temperature would begin to rise quickly, sometimes all the way up into the redzone. Ive tested it by just starting up the car in the driveway and the temperature gauge would not stay at a quarter, it would go up to full hot, at the point and only on the full red, the cooling fan THEN turns on and it cools down. But it is weird though, because the gauge when its "hot" it bounces like its unsteady at hot, and at times im driving and it bounces at hot, then juts down to being steady at a quarter. If anyone has any clue of whats going on, please respond.

What I have done to rectify the situation - replace the thermostat/flush the radiator - put new coolant in = problem still happens

My only guess left is possibly the temperature sensor?
Thank you for your time.

Mr. Avionics

Had a somewhat similar problem when I first got
my car last Oct. Would get hot when driving
arround town, but cooled down when I turned the
AC on. Fan was not coming on unless AC was on.
Problem was the thermo switch on the radiator
that controls one of the fans. Replaced it with
the lower temp switch from Performance Products
and the problem went away. Also clean/wiggle
the wire on the temp sensor, not the best design
of a connection and easly gets corroded.
Good Luck,
Bill

dek944

Thanks, I'll buy the low temp thermo switch amd also check the wire.

Leigh 13

Dek, I had a similar problem as you and a new thermostat fixed it. The low temp fan switch Bill suggested is a good bet too.

dek944

I was wondering if you have a direct link to the performance products site with the switch, because I searched and all I can find was the swithc wrench.

dek944

Yea, I replaced the thermostat, but that did not seem to resolve the problem. Should i buy the switch or the temperature sensor. Does anyone have any clue as to why it bounces when its at hot also?

jenket944

Similar problem for me, but its the oil pressure gauge that's going crazy. It holds steady, pegged at the max when on the throttle. However, when the engine rpm's drop back down to idle the gauge starts bouncing wildly between max and where it would usually be during idle (between the 3 and 4 mark). Plus when I kill the engine, the indicator stays pegged at the max and doensn't drop down to the miniumum point like all the other gauges. Weird...

turbokev

My Oil Pressure Gauge was doing the same thing.. it was a bad sender unit. I think it was about $60 to replace it and the gauge works fine now.

My Temp gauge this morning was doing some jumping around.. Once the car came up to normal operating temperature it suddenly clicked to WAY hot, then clicked back down to normal. It did this a few times. It was like 0 degrees this morning and it's never done this before. It certainly looked electrical in nature..I don't think the engine was actually fluctuating in temp that much back and forth.

ahofam123

My temp guage rises to just beneath the red zone. I knew that the car wasn't overheating because I had just finished replacing the entire cooling system. Anyways the fans don't come on until the red zone and when I took various temperatures of the head at this point, the range was between 150 deg. F and 180 deg. F. I'm thinking that my problem might be the sending unit. Any suggestions?

Leigh 13

Dek, I don't have the Performance Parts catalog on me, so I'm not sure of the specific part numbers. I know that I got the low-temp fan switch and the low-temp thermostat. The PO of my 944 replaced the thermostat right before I bought it, but it might not have been for the right temperature because a new one fixed the overheating problems I was having.

Regarding the temp gauge "bouncing" - mine used to do that, and often a nice smack to the top of the dash right above the gauge would set it back to the right place. The electrical system in older 944's can get pretty flaky (no surprise, being almost 20 years old!) so you might want to check for any problems with the grounds.

Here's some more on the subject that <a href="http://forums.pelicanparts.com/showthread.php?s=&threadid=11045&highlight=thermostat" target="_blank"> I posted</a> back in November 2000:

I used to have terrible trouble with overheating in my 944. It used to run consistently at the 3/4 mark when driving, and hit the yellow zone at idle. The previous owner had replaced the fan switch, thermostat, and radiator, so I figured the solution had to lie somewhere else. Especially interesting was the fact that the temp guage would jump about 1/8 whenever the lights were on. Perhaps a bad ground somewhere?

Last month I had a complete service job done for 75,000 miles. I gave the mechanic a new lower temp fan switch and thermostat I got from Performance Products to replace the existing ones. The fan switches turned out to be identical, and didn't fix anything--even with the fan shorted to run at all times, the guage would never reach as low as 1/2. The thermostat turned out to be a different story, as the temperature now measures below the 1/4 mark when driving. In traffic, it has yet to reach 1/2.

So yes, I agree that the thermostat can often be the solution!

Hope that helps!

- Leigh

944Play

Definitely start by cleaning the main ground terminal on the bellhousing, underneath the heater valve. Yes, it's a PITA, but if this connection is not solid, it will cause all sorts of weirdness, especially a temp gauge that bounces/floats upward.

Don't drop that nut. <img border="0" title="" alt="[Wink]" src="wink.gif" />

EDIT -- check <a href="http://forums.rennlist.com/cgi-bin/rennforums/ultimatebb.cgi?ubb=get_topic;f=15;t=015735" target="_blank">this thread</a> out.

EricFeazel

If your gauges jump...this is really simple. Replace your Battery to Engine ground and your engine to body ground. People always overlook the eletrical side of things and yet in our cars are one of the most problematic places.