Strange overheating problem
 

Just bought my first Impreza (2006 hawkeye wrx 2.5)

Thought I had been royally done over, however now I think there is probably a simple explanation

Symptoms

-Engine stays in middle of gauge when driving above 3k no problem, blower in cab gives out warm air

- drop below 2.5k for 20-30 seconds and gauge shoots up and heater blows cold.

- revving engine gets up relieves problem(no load) or simply acceleration under load also clears problem.

- everything seems normal under radiator cap.

- expansion tank is a almost full ?

I suspect that this is an air block somehow, however have never encountered an intermittent air lock like this before.


Anyone had a problem like this?

I would suggest getting a sniff test done,could be the start of head gasket failure.
Did you do any research on the 2.5 engine?

I will get a sniff test done asap

However, I really don't see how it could be the head gasket.

All the experiences of head gasket failure I've had the misfortune to encounter get worse with RPM and load

Never the other way round, also the heater matrix doesn't stop working inexplicably then start working again.

There is no oil in the coolant and no bubbling

Any other ideas

Maybe water pump on the way out? They have a habit of the impellor coming loose.

I had an intermittent overheating problem for a yr and ended up a headgasket ! Only take a tiny pin hole to start !!

Possibly an air lock - make sure the overflow hose is actually sat under the coolant level in the overflow plastic bottle at the side of the radiator otherwise it can suck air into the system.
Make sure the rad cap and header tank caps havent been swapped over - header tank cap has the vacuum valve on it.
Do you get a water rushing noise when starting from cold from behind the glovebox ?

Mick

i had this problem after doing a radiator in my old scooby, kept overheating, and after a while i figured out it was an air lock up at turbo, i took turbo water pipe off and filled the pipe up, stuck it back on and never had a problem again, hope its something simple mate

This is a common on 2.5 I would suggest coolant and thermostat change first check the bottom hose to see if it's warm