Could anyone give me any advice, i have a 98 impreza turbo?
While the car is stationary everything heats up fine but while it is being driven the radiator doesn't get warm, the heaters go cold after about 5 mins and the engine starts to overheat. The water pump, thermostat and radiator have been replaced and the engine has been flushed. A garage has checked the head gaskets and they said they were ok.

 

Sounds like an airlock, which is more than common when the system has been emptied/flushed/refilled, usually by someone who doesn't know Imprezas.

My advice to you would be to drain and refill. Do a search on here under my username for "How to" without airlocking.

Use a decent anti-freeze mixed 50% with water, and ask for one with a corrosion inhibitor and suitable for alloy engines.

Be careful: THERE IS NO KNOWN WAY TO BE CERTAIN OF BLEEDING THE COOLING SYSTEM ON AN IMPREZA!!! You will get folk on here who will tell you, "I did X, Y then Z and it worked...". Good for them....but they were lucky, you may not be.

So do it right...and don't drive it (far) without doing it, since if it overheats, it will knacker the hg's...and that's NOT cheap

 

You could have an air lock and it sounds ver like it. You'll see a rubber hose that runs from the top of the header tank and goes to the turbo. Take the end off from the header tank, hold it upright and fill the pipe with coolant. Engine cold of course! I used a funnel stuffed in to the pipe to make things easier. This is the best way to fill the system. Take the cap off the header tank so you can see when the coolant level rises.

 

Thanks, will drain and try filling through this pipe.

 

You'll need about 7 litres as far as I remember. Measure it out in to a couple of containers before you start. That way you'll know exactly what you've put in and if it's near the required 7 litres.

 

I'm writing in invisible ink again, then..........

 

Why would you say that?

 

Thanks alcazar, took me a while to find your post, which type/brand of antifreeze would be recomended?

 

Most people would probably say use genuine Subaru anti freeze. I used blue anti freeze from euro car parts as it meets all the requirements for the engine. As alcazar already posted, 50/50 mix.

 

a blanket 50/50 mix is very wrong IMO as different companies sell different strengths of concentrate.....................

we use & supply Millers A/freeze (as well as distilled Motul Inugel) and to get the best balance of cooling and frost/corrosion protection the mix is 35% a/freeze to 65% water..............

glycol is NOT a coolant which is why these "waterless" coolants are often not.........

 

As above: I should have said, my coolant was pink/red, came from a reliable Motor Factors, and the instructions said 50/50.

Ask at your local place: suitable for an alloy engine, corrosion inhibitor, then read the instructions about mixing it.

It's a while since I did mine, but I THINK it was Comma.

 

Thanks for the advice, will have a look round for some.