danny951

Last couple weeks my 951 has been running a bit hot. I thought my previous oil leak problem would have fixed this, but apparently not. Prior to a few weeks ago, I'd never see the temp gauge get much past the first line, whereas now, during a drive on the highway, I'll see it get halfway between the first and second line, and when stopped at an intersection during city driving, it gets dangerously close to that second line.

Now I hear the fans running, but I'm not sure how many fans should be running and if they are all running as they should. My coolant tank is filled to the "max" line, though I should note that the last time I put coolant in, I didn't let the car quite cool off enough and when I took off the pressure cap, coolant was sucked into the overflow tank from the engine (or wherever?). DI

Luis de Prat

How old is the thermostat?

Ski

I'd agree to check the thermostat...if you turn on the heat, on high, does the temp go down?

alex_cristocea

I had the same problem last month.I changed thermostat cooling fan relays and still nothing until I pulled out the radiator for a good cealning inside and outside.The radiator grils was full of insects and derbis that you could not see un the other side.I also replaced the termofan switch and now car runs fine.

DAR951

Trapped air. Our cars are notoriously hard to bleed. I chased a similar problem for a long time before buying a vacuum filler/bleeder... Never had a problem since. Something like this: http://www.thetoolwarehouse.net/shop/MIT-MV4535.html

Keithr726

Check the real temp of the engine using a laser gun type reader. My car rarely meets the first line.

NeoRules

I thought my car was overheating (87 951) but the shop stated the fuel and temperature guages are both bad.... I am going to put a regular old fashioned temp guage in a pod somewhere....
JC

LFA951

Mine stays at the first line during regular driving and it gets just above it at lights. I think it might be one of your fans, check to see that they are both working when the temperature rises...

jerome951

Doubtful it's the thermostat. When they fail, they fail closed and you cook your motor.

As DAR said, make sure the system is bled properly. If you don't have the vacuum bleeder like DAR linked, you can try this method: get the front end in the air, engine cool, crack bleeder screw on top of the head (leave the wrench on it), remove rad cap, clean around the cap area, pinch off the coolant tank overflow, then seal your mouth over the opening and blow hard. You should hear the coolant spitting out of the bleeder screw. Close the screw before you stop blowing so you don't suck air back into the system. Repeat until you only have coolant coming out.

Warning - do this only in the confines of your garage w/ the door closed. You don't want friends or neighbors seeing you pleasuring your car...

Alternately, you can park on an incline (front higher than the rear) w/ the engine hot and running then crack the bleeder screw. However, I find the first method to be more effective.

If the system is bled and you've ensured the radiator is not clogged in front, my guess would either be a bad headgasket or failing waterpump.

The last thing to check is to clean your electrical grounds. The temp gauge is sensitive, so any resistance in the grounds will make it read higher than actual. However, since your fans are coming on (not part of the same system) it sounds like the car is actually getting hot and it's not just a false reading on the gauge.

Bob_in_Chicago

Just where are these engine electrical grounds? A picture would help me find them. Thanx in advance!

ehall

+1 gazillion. Pressure test the coolant system. Either it has a leak you can't quite find without pressure, or there is trapped air. I've done this a number of times due to different maintenance jobs. It takes atleast twice as much bleeding effort as you would think. Bleed, cap. Do it again. repaet and rinse.
I'm saying this especially because you've recently done work on the car.

jerome951

Sorry, Bob, no pics but the main ones aren't too hard to find, just hard to get to.

The main engine grounds are on top of the bellhousing just inboard the speed & reference sensors. Easier to get to w/ the intake manifold off but not impossible. Be sure to cover the flywheel TDC opening in the top of the bellhousing or you WILL drop something in there (ask me how I know).

Main chassis ground is on backside of firewall just inboard of the battery.

If you can't find either of the above, just trace the cables coming off the negative terminal of the battery.

Instrument grounds are under the dash inboard of the cruise control brain. You will have to lie on the seat w/ your head in the footwell to see them as they're tucked up under the dash. There should be a gold-colored coating where they attach to the dash. I'd recommend not rubbing off this coating.

If you have any gauge jumpiness (especially a low reading volt gauge), clean the grounds well and it may solve the problem.

Bob_in_Chicago

BINGO! "If you have any gauge jumpiness (especially a low reading volt gauge)" That's me.

Three gauges: temp gauge, oil press, & voltage all jump when I drive over highway bumps. Thanks Jerome.