A few days ago I was stuck in heavy traffic and the engine overheated, where I discovered the lower radiator hose had popped off at the radiator end dumping all the coolant. I managed to refit the hose, chuck some water in and nurse her home very gradually. I since refitted the hose properly with new clips, refilled with coolant and burped it all properly. However, on a few runs the coolant pressure seems to build up a lot and coolant wants to escape from the hose join.

It seems to be worse if I've had to use any sort of power when driving. If I go in ultra-miler mode (not what a Scooby is for!), it just about holds up.

So I'm now suspecting a head gasket is on its way out, as gases are getting into the cooling system. I did have HG failure a couple of years ago, which caused the engine to overheating and the overflow tank to get filled up. However this time the overflow tank isn't getting any extra coolant in it. The top radiator hose does feel very bloated after a run.

At least this overheating issue had solved my previous query about the engine underheating, as it seems my temperature gauge is faulty and under-reading by about 50%.

 

Airlock? On classics you have to back fill via the turbo coolant pipe. There is no way to bleed/burp the system.

 

Fans cutting in? Both mine failed this summer

 

It's a Blobeye WRX EJ205. I filled the coolant up using one of those deep funnels which I had plenty of coolant one while I ran the engine to get the air pockets out. I've used the method before a few times without any problems.
The fans cut in OK, and the thermostat seems to open when warm as expected.

If the pressure rises too much I would expect the radiator cap would release pressure into the overflow tank surely?

 

Take the overflow pipe that runs from the metal header tank and remove it when the car is warm. Then get a long piece of pipe the same diameter and run it from the header tank and out of the engine bay and place it under the passenger wiper. Then go for a spirited run if you have problems you will find excessive water squirting out of the said pipe. Try a new rad cap to

 

Im guessing crap around pump to hose joint, clamp not tight enough.

 

Just tried this now, and went for a bit of a drive. I saw coolant getting to the tip of the hose, but even when giving it some welly it didn't squirt out. Maybe I should have gone for a longer drive and get the engine a bit warmer too when I've got a bit more time. Both radiator and header caps are only a few months old so should be OK, and look fine.

 

I did take the thermostat housing off to give it a clean and check the thermostat, so the hose should be well clamped up. I just tried nipping up the hose clamp and it seemed nice and tight.

 

Is it possible to mix up the radiator and header tank caps on your version?

 

Car needs to be warm when done as in warm before you take the wee pipe of the neck of the header tank
It might be only stating to fail but hopefully not.

 

There are more common weaker places typically when its HG gone, bulging of top hose after a spirited run is a bad sign, heater matrix leaks,
many times I can remove a rad hose clamp and still struggle to twist the hose free, so it seems strange a fully clamped hose leaking.

 

Rad cracked near or around bottom hose?

 

No cracking on the rad, and it's only a couple of years old.
The caps on the radiator and header seem to be not swapped.
I tried the trick with the hose connected to the header breather again, and did it when the engine was warm, then went for a blast (though the icy roads did limit that!). There was no sign of any coolant squirting from the hose.

 

Just did some research on the caps, and while my header cap is the correct two-way valve one; the one I had on my radiator was also two-way. I found an article saying that the radiator one should be a one-way valve type, otherwise air can get into the system. So I managed to find a cap from an old radiator I had which is one-way and fitted that instead. Went for a reasonably normal drive for 30 mins or so today and it seemed to survive OK. I'll keep a close eye on things while driving a bit more 'interestingly' over the next few days or so.
Fingers crossed this was the problem.

 

Hope you sorted it #closeeye#subaru
😬😀