A4 Oil and Coolant Temperature Guages

[Raiters]

I hope some one out there can help me with a problem that I have with my '96 1.8 A4. Both the engine oil and coolant temperature guages on my dash have been reading low, typically 60C. I have replaced the sensor unit in the engine, but this has not fixed the problem at all. Can anyone advise me on what to look for next?

[Dave Avant]

Even in cold weather if the thermostat is working correctly in the coolant, not sure if the oil cooling is controlled, the water should be around late 80s to normally 90 degrees, the oil will be about the same, if on a longer run or motorway work it should go above 90-100 degrees.

Are both temps the same? Have you felt the coolant pipes? A stuck stat will keep the engine cool, sometimes around 50-60 degrees. Does the temp rise in traffic or when pressing on and cool off when cruising? A cool engine, more so if the oil is water cooled will keep the oil cool too.

[Raiters]

Thanks for the response. When I am struck in traffic both guages rise to almost 90c and when I start off again they drop back to reading almost 60c. All the pipes in the engine are hot and the coolant appears to be boiling, or certainly there is plenty of steam if you release the top of the coolant reservoir (obviously done carefully)! Do you think it is a thermostat problem as opposed to a wiring problem in the dash?

[adamss24]

Hi, i believe your car's cooling system behaves as it should and you worry for no reason ! Regards !

[Dave Avant]

I would guess at a stuck thermostat. 60 degrees is too low for operating temp. It will be fine, but could be using slightly more fuel.

Most thermostats open at around 86-92 degrees, high performance and tuned cars, like the Lotus Exige had a 78 degree stat which is considered to be quite low and is specified to try and keep it cooler. BMWs typically use a 90 degree stat. Running the engine at 60 degrees the oil will not burn of condensation increasing water oxidisation in the engine. some engines can have mayo on the dipstick like signs of head gasket failure due to not warming up properly or doing very short journies, this is the condensation not burning off and mixing with the oil.