1985 Porsche 944 with cooling problem

I have an '85 Porsche 944 with a temp gauge going crazy. At idle, the temp gauge gets very close to the red zone before the high speed fans kick in and bring down the temp. This is after replacing the fan switch, water pump, radiator, thermostat and temp sensor. Today, the fans kicked in but the gauge did not return to the normal zone. As soon as I resume driving however, the temp gauge returns to the normal zone. Any and all help truly welcome. Thanks.

Old hoses can sometimes collapse internally and not be visable outside. Their construction is a fibrous sheath with an internal liner, and the liner can fail.
Try a new radiator cap and new hoses. If that doesn’t fix it, perhaps a compression leakdown test will solve the puzzle.

By the way, have you performed a pressure test of the system? Have you been testing and/or inspecting the removed parts in any way to confirm that they’re bad?

Thanks for the quick response. I’ve been relying on a mechanic, so I haven’t seen the old parts (my negligence). I will check the hoses, replace the cap and pressure test as you recommend. Your guidance is truly appreciated–thanks.


You’re welcome.

You won’t be able to check the hoses without removing them. Perhaps not even then, at least not without slicing them. Fortunately, they’re affordable to replace.

Got it–thanks again!