Overheating while stationary
 

Recently on an airport run I noticed my water temp gauge needle creeping up to the top, apart from sitting just below half way when the car has warmed up I've never seen the needle move before.

The car overheats only when stationary and returns to the normal temperature when driving.

Yesterday I dropped the coolant and changed the thermostat while I was at it (filled from the rear most pipe on the header tank, no glugs etc) however the problem still persists.

When the radiator fans start up there is no hot air being blown away, the radiator is cool to the touch however the heaters do push out really hot air.

I was thinking of getting a sniff test done next to rule out HG failure, is there anything else I can try before taking it to a garage?

It's a 2002 STi Type UK.

Thanks in advanced.

I'd say you have an airlock unless you toasted it at the airport but I guess you must have switched it off soon as you seen the needle creeping up?

Yeh, turned it off right away at drop off!

I've heard of a few radiator cores furring up and blocking, but I think a sniff test would be the best move, just in case.

If its the radiator then I'd obviously replace. How are these japspeed ones like? Worth getting?

Look for a fully alloy one like a Nissens.

I got a cheap one (about £50) from cool parts uk. Looks really good quality and virtually identical to oem. But I'm not running anything that would generate huge temperatures.
I also say, get a sniff test first. I've heard of a lot more head gasket failures than knackered radiators.

Assuming you have no leaks etc then if you see your needle shoot up high then the damage has already been done slightly and will over time get worse as the needles in subarus go high too late IMO .

Sniff test won't always show up if slight hg issues, mine didn't anyway.

Any loss of coolant into expansion tank etc?

Don't those cheapo, all ally ones warp and buckle?:wonder:

When mine needed replacing, I opted for OEM - as they are good for at least 10 years, before you might get problems (e.g pinhole in plastic endtank, etc.)

Nope, the expansion tank level hasn't changed at all.

If you loosen the top hose and move it does water come out? May be worth draining again and fill the radiator through the top hose and fill the block through the top hose connector slowly until water is in the header tank. Refit the top hose and top the header tank up whilst gently squeezing the top hose to push air out. I spent some money and bought this kit as I had two cars to do the timing belts on.


http://www.ebay.co.uk/itm/Cooling-Sy...wAAOSw0e9Ut5kN

If you go for a spirited country drive, check the expansion tank to see if it's bubbling.

I had an intermittent overheat problem caused by failing head gaskets, but that was on a 2.5l which are notorious for it.

Might also be worth checking the cooling fans. If it only happens when stationary the engine relies on the fans to cool the rad, but when moving the airflow over it might be enough. Do they come on if you leave it idling for a while?

Yeah they do come on however the air they pull through the radiator is cool.

How cool is cool? If the rad isn't really getting hot, it could be the thermostat? A dodgy stat that's not opening would certainly cause overheat.

The Thermostat was changed at the same time as the coolant.

Just to go back to my earlier point about radiators, if you look at the sides if the radiator and they appear to be bulging out, rather than straight up and down then it's probably either knackered or close to it.

Yes, sorry you had mentioned about changing the stat already.

I'm not sure the arrangement on scoobs but I've seen it before on other cars where the water pump vanes have detached from the pump drive shaft so the shaft was rotating and the vanes were moving much more slowly or not at all, dragged only by the friction between the two. This could mean that at idle the vanes do not move, or move so slowly they do not pump any coolant, but at higher engine speeds the vanes move slightly faster pumping a little coolant through to the engine, that might explain how it's only happening at idle and not when driving?

Just a thought and not sure how to check it other than pulling the water pump out.

Interesting, on the way to the garage this morning the temps started to normalize so it's very intermittent. Hopefully will find out what the issue is later today.

Might have to make a purchase :thumb:

Hello, did you get to the bottom of this?

you dont need one of these to refill and purge the cooling system on a Subaru, no idea why people claim to struggle.

:thumb:

Having same issues over past year my coolant temp hitting over 100 about 4 times car booked into subaru next week for thermostat and coolant change so hopefully it's just a sticky one car only done 29000 2.5 hawk

It has a air lock , Scoobys are an ass to bleed sometimes, if no hot air in heaters then there's no hot water in the matrix therefore there's an air lock in the car obviously

Imprezas cant be bled...

Its been filled wrong if there is air in the system and it needs draining and starting again

^^^This.

Indeed I did, a small split in a hose that I couldn't see. £20 later and all is well (plus a sniff to be on the safe side)

Coolant was released and then filled from the rear most hose on the header tank to the turbo. Filled slowly to ensure no air was being pulled in.

Glad to hear it wasn't anything too expensive!

Me too!