Over heating when driving only
 

Hi. New to the forum so hopefully this makes sense. I struggled to find many answers to this elsewhere.

I've just got a 2004 WRX. It had lost it's coolant after the top hose burst where the rad fan had worn away at it til the point it popped.

Anyway.. I fitted a hose and then filled it with Coolant, following Alcaraz's helpful guide.

So it was filled up slowly, then run up to temp til the fans came on and the heater was lovely and hot. It had been running for a good half hour and the temp guage was perfect.

Then I went up the road for a sensible drive and all of a sudden the heater went cold, and the temp gauge started to rise quite quickly. It had pushed the coolant into the over flow tank. I've done this whole process twice and it's happened both times. Only when driving. Am I now looking at head gasket? It runs perfectly, doesn't smoke etc. But I'm new to these! So any help please?

Sounds like head gasket.

When it originally lost its coolant with the split hose, was the engine hot at the time? Did you refill the coolant straight away to cool the engine down?

There's often the risk for overheated engines that if you try to cool them down quickly by pouring back in cold coolant/water is that the head(s) can warp. The result would often be an ill-fitting head gasket seal.

Did you ensure all the air was removed from the cooling system?

You need to burp your coolant system. You have more than likely got air in the system as these things are notoriously prone to this. Have a look online and burping subaru coolant system and get yourself a proper coolant bucket to do it correctly.

Agreed, sounds like air to me, and it can be quite tricky to remove so a proper coolant bucket will really help particularly if you don't want coolant all over your engine bay.

Does it seem possible that it could be an air lock both times then? It's happened on both attempts. O thought I did it apot on second time. Filled slowly through the rear pipe etc. Then some pipe squeezing too.

I actually bought it as it was. So I can't say for certain how it was dealt with when it lost it's coolant. Was a bit of a punt.

If it was the head gasket would it overheat when idling as well? As it can sit there for half an hour ticking over at the right temp and be fine.

Then only over heat within 5 minutes or so of going for a drive...

On a subaru you can't get the air out by squeezing the pipes. You need to burp the system.

Get one of these, they are great.

https://cimg9.ibsrv.net/gimg/www.sco...bbf7e23695.jpg

Have a look at this thread & video

https://forums.nasioc.com/forums/sho....php?t=2437371