172 erratic temp gauge!!!

[tonyw]

Hi all, for the last few days my temp gauge has been misbehaving.

During normal driving the needle goes up to just below max temp then slowly drops over a few minutes to just below mid temp. Have checked coolant levels and all okay.

Its due the 72,000 service in about 2 days and Im hoping that resolves it. Anyone come across this before??

Ta

 

[tonyw]

Anyone?

 

[toms123]

Ever since i got mine my temperature guage would get very high as i was driving it about but as the speed rose it would cool as the wind was blowing in a cooling the engine. However, when i came to a stand still i had to put the heaters on full incase of overheating! Now that i have fiddled with the cold air feed to the induction kit it remains nice and cool all the time - although my fan is broke - oops!

 

[BenR]

Check the CTS and the head for air locks.

 

[JAY172]

if coolant levels ok then most likely a coolant temp sensor fault.

 

[RPM]

I have had the same problem, engine nice and warm then suddenly the temp gauge drops to half of normal temp. Has been ok for 2months though???

 

[NIN-172]

My last car used to do that.
My theory:
The engine warmed up & when it got to a certain temp the thermostat opened, & let the colder water through direct from the radiator. Hence temp level drops.

 

[BenR]

The thermo opens slowely and gradually, so there is no sudden blast of cool water.

 

[JAY172]

Quote: Originally posted by NIN-172 on 09 May 2004

My last car used to do that.
My theory:
The engine warmed up & when it got to a certain temp the thermostat opened, & let the colder water through direct from the radiator. Hence temp level drops.

the 172 temp gauges seem to get up to operating temp and stay there even when the engines hot enough for the cooling fan. a large fluctuation of the temp gauge normally indicates a problem. also as ben says the thermostat opens gradually so you wouldnt get a rush of cold water into the engine. a sudden rush of cold water into a hot engine could cause things to crack.