strange coolant temp problem
 

Hey guys, need some help here. Searched here and at rennlist, but no luck. My 87 951 has a strange hot running problem. Start the car up and it can idle for ever and the temp never goes above the middle of the gauge (9 o'clock position) Start driving it and when it gets some load it rises to the top white mark on the gauge. Pull up to a stop and the temp starts comming down. Drive on the highway at 70 mph and the temp sits at the top white mark. Give it some load on the highway (like up hill with some boost) and it goes a little over the top white mark. Take and exit off the highway and come to a stop and temp comes down pretty quickly to the middle of the gauge.

This seems pretty strange, it cools down while idling at a light, heats up when on the highway.

I have replaced the pump and thermostat and bled the system many times and also had a shop look into it today. They bled it and said it was okay. Problem is they drove it around town stop and go so it never heated up much.

Clearly the fans work great because when the car is not moving it cools down!!

As a side note I have an intermittant heating problem. Sometimes there is heat in the car, sometimes not. When it is first started the heat seems to work, after driving for a while, it is intermittant. Today the shop said the control panel was malfunctioning and the two problems are not related.

I have bled the car hot and cold with pressure and without. The shop today bled it as well.

Where should I look next??

Cheers

Hey Jeff,

I would try a compression check. Do you lose water?

Compression test was done, it was fine and even on all cylinders. No coolant loss what so ever. Lawrence suggested the lower hose maybe colapsing so I will replace that and see what happens.

Thanks

Just an update. It was a plugged radiator. Had it flushed at the local rad shop and all is well now!

Cheers