Overheating Issue, Can't work it out.

[Dropz]

In my experience, and every mechanic I've ever spoken to, a TK tester is as accurate as a blind guy with no hands in a shooting range.

Subaru headgaskets are shit, we all know this, but 98% of the time it only fails between the rear lower oil gallery and the external of the engine, causing an external oil leak. There is rarely damage between oil and coolant galleries, and just as rarely coolant leaking into the cylinders.

Chances are part of your cooling system is blocked and needs flushing/ replacing, or the thermostat or water pump need replacing.

[The Sean]

All of those have been done thus far (thermostat first, flushed radiator second, hole in after-market thermostat diaphragm 3rd). The hole in the thermostat seems to have sorted it but it's the unknown as to whether it is enough on long drives (highway spped, relatively constant revs) that has made me decide to fix it.

Cheers for the info but, it is appreciated but I think the damage has already been done.

[Vuk]

Hey all,
Sorry for the late reply, have been quite busy.
Thanks for all the replies.

2 days ago I replaced the thermostat and radiator(brand new). I am still getting an overheating issue after about 30 minutes of driving.
When I accelerate going up a hill I can hear a "sloshing" which bring me to the conclusion that I have an airlock somewhere in the line.

I am going to flush the coolant tomorrow and see if the thermostat is the problem, should I cut the nipple off of the thermostat as well as drilling additional holes? If so what size holes and where about do you drill them?

Thanks heaps for the answers guys.

[Dropz]

Don't modify the thermostat at all. Find a funnel or bottle that fits in the top of the radiator snugly, fill it with coolant and run the car upto operating temp revving at about 2500rpm. when the fans have cycled in and out twice rev the car up and down a few times, then stop the engine and let it sit for another 5-10minutes. just give the top hose a squeeze to make sure no more air bubbles come out, fill up the overflow to the top - yes, way overfull. go for a 20 minute drive, around some hills if you can, changing the load regularly; cruising, accel, decel, engine braking etc. and then re-evaluate for noise. at home, when I have an airlock this is my sure-fire method that hasn't failed yet.

At work I disconnect the cooling fans, with the select monitor hooked up watch the coolant temp and when it hits 100degrees I plug the fans in (engine still running) give it some revs and wait til the fans go off. never had an issue with this either. and its alot quicker too but you need something to monitor the coolant temp. And if you do let it get too hot obviously it can be dangerous for the engine.

[Gards]

Speaking of coolant fans have you checked the radiator cooling fans are working and coming on when the car radiator heats up (i.e. stationary in traffic)