rshanholtz

The water temp gauge is being very erratic. Going from normal to redline in jerky movements. When the car is on the highway cruising, the gauge appears normal, when idling or around town, the guage has jerky movements and then slowly climbs to the red. My coolant level is fine. Additionally, neither one of my cooling fans appear to be working. I have checked both fuses and just had the relay replaced. Whether the engine is running or just shut off after a good run, neither of the fans are on. Are these related issues? Any one have any ideas? I did just add the MOCAL extra oil cooler but I do not think that that would have any bearing. Help as always is appreciated.

Ski

Check the thermal valve, the plug on the right side of the radiator looking down, two prong switch and see if it's unplugged or it could be that switch. Do the fans come on if you turn on the AC? You might double check your install and make sure you didn't cut a wire to the fans.

It also sounds like a bit of air in the system as well, could also have a bit to do with the internal seal of the water pump, when the thermostat opens to close off the bypass - how old is the water pump? If around town and you turn on the heat, does the temp go down?

PEvans

Iceshark used to say erratic gauge readings could be due to a poor ground.

I finally got one of those infrared laser thermometers and idled the car for a while to determine the head temperature at which the fans would come on at. At least that gave me peace of mind.

rshanholtz

Thanks PEvans and Ski. I will drive the car to work tomorrow and play with the AC and the HEAT to see if I can force the fans on. It is still pretty cool here on the NE so I should not overheat. I also installed a seperate water temp gauge in a 3-gauge cluster below the radio and it too is showing that car will reach 200 degrees when the OEM needle is in the red.

jerome951

Quite likely the grounds need to be cleaned. Clean the one under the dash (just inboard of the cruise control brain: you have to lay in the footwell to see it) and the 2 on the clutch housing. My temp gauge does exactly this when the grounds are in need of a cleaning.

Luis de Prat

It's also a good idea to check the cooling fan/AC relay and see if it's getting hot or malfunctioning. When they go bad, the cooling system goes haywire.

Cory9584

Another cool idea is to install a switch to jump the fan relay and make the fan come on and stay on till you turn it off. This is good for when you want to keep the engine cool on a hot day and not wait for it to hit the point where the fan comes on.

PEvans

FWIW, I found with my '86 951 that the fan came on at about 197F and turned off at about 193F measured at the water neck with the infrared thermometer and with the car stationary (idling) and no AC. I don't recall now, but I think that may have been the low-speed fan only; I don't think I ever got the high speed fan to come on. That's roughly consistent with the spec - the low speed fan is supposed to come on at 92C.

badass951

Can you explain in further detail?