My Subaru overheats. Why?

[Simon2015]

Hi everyone,

I have a 2008 b3 hatcheck that overheats.

The coolant temperature warning light starts to flicker when I go up hill. I also noticed that if I drive at HIGH rpm it happens LESS. I've replaced the radiator and the thermostat and it didn't help. I did a head gasket pressure test and no leak was found.

The mechanic at the garage said that it might be the head gasket although the test was fine. He says that it might be leaking only when the engine is working really hard and that is why he could not detect it in the test.

Replacing the headgasket costs lots of money.

I think that since the engine overheats less when I drive on high rpm, it could be the water pump (broken wings)?

Thank you guys.

 

[Rik]

Simon2015,

 

I would have thought that if the water pump had broken wings you'd tend to hear the clattering noise from within and

damage would be prevalent.

 

I know you've had a pressure test done but did they check for combustion gasses in coolant and are there any signs of

oil /greasy residue showing on internal walls of header tank, or even on the internal lip of the NEW radiator filler area?

I assume rad cooling fan is working correctly?

 

Are all fluid hoses clear of any obstruction, or maybe even pinhole damage?

 

Run the engine up to operating temp whilst parked on level ground, get some one to rev it (within safe limits) and watch the coolant header tank. If it starts to ooze out from the overflow then start doing the relevant tests for HG failure.

 

See my post here:- http://uk.subaruownersclub.com/forums/topic/16548-whitegreyish-gunk-in-water-res/

 

Regards,

 

Rik.

[Simon2015]

Thanks for the explanation Rik!

I checked for residues in the header tank and in the radiator cap.

The radiator was pretty clean but the header tank had some sort of mud on the walls yet it didn't really felt greasy or oily, just mud.

I tried to run the engine for 10 minutes at low rpm (0.5) then 5 minutes on 2 rpm then 5 minutes at 3 rpm and finally another couple of minutes at 4 rpm (was pretty noisy) and nothing happened. No blinking light and no movement of the coolant level in the header tank.

But earlier this day I drove up a steep hill for some time then the temp' light began to blink so I stopped and checked the coolant level and it was over flowing.

I don't get it. What happens when I go up hill that doesn't happen when I'm just revving the engine. Maybe I didn't rev it for enough time?