This summer my temp gauge is going 3 or 4 ticks to the right of center when driving around the city. Highway speeds make the temperature go back to normal (one tick to the left of center). Before I take my mechanics advice and pull the front end of my 97 A4 2.7 off to replace the thermostat I wanted to find out if it is something easier. The thermostat and water pump were replaced 2.5 years ago.

It appears to me like the coolant is not circulating correctly. The large hose coming out of the radiator is soft when the car is running. My friend told me that should be hard. Is that correct?

A lot of pressure builds up in the coolant reservoir. Enough pressure builds up that the coolant has started leaking from a small crack in the reservoir. However the coolant has not come through the relief on the bottom of the reservoir.

I am not getting any error codes and the car is driving fine.

Any help would be great.

 

not correct. as long as its not rotten or leaking, soft is fine. rubber gets softer as it heats up.

there shouldnt be much pressure at all in the coolant expansion tank, and it certainly should not be leaking. if its cracked you should replace it.

also while you are at it i would replace the coolant temp sensor first. its a fairly cheap part and it does die every once in a while. do that to make sure that your temp reading is actually accurate before diving into the water pump/ thermostat job.

 

I guess what I meant by "soft" is that I could squeeze it. My friend said the system is pressurized so you shouldn't be able to squeeze the hose when the coolant is circulating.

I actually change the coolant temp sensor already. That didn't fix the problem.

Thanks

 

Highway speeds the car temperature is fine, but only when driving at slower speeds the temperature goes up. Do you know if the auxiliary fan is kicking on?

 

The auxiliary fan is definitely coming on. It is very loud. It comes on often.

 

it shouldnt come on that often when the A/C isnt on. are you sure the vicious fan clutch is good? that fan should be spinning pretty fast whenever the engine is on.

 

Yeah, if the temp drops at highway speed, my guess would be the fan isn't working as good as it should be. It sounds like it's not pulling enough air through the radiator when the car isn't moving fast enough...