1996 Subaru Legacy – EJ25 Misfire

OK guys so here is an update after a new thermostat. I filled the cooling system slowly with the little little bleed screw on the other side of the radiator out. Filled up the the overflow to the right level, started the car and let it run through a few fan cycles before I took it for a spin.. everything was fine, the lower hose was warm which ment the new thermostat was working fine, overflow was keeping a good level. So I then jumped in the car and went around the block a good few times and up some steep hills. Engine was still spluttering with its misfire.. but anyway the temperature gauge stayed normal the whole time I was out, and all was well until I got home. I parked up the car, popped the hood, and found the little hose for the overflow which pushes onto the radiator cap neck had popped off and the coolant has sprayed out. Now either there was a tonne of pressure in there, or it was loose… It seems loose when I put it back on. But the overflow bottle was full, the lower hose was cold, top of radiator was cold, upper hose hot and I released the cap (CAREFULLY) and slowly with a thick rag and there was so much pressure that came out. I am not sure what is going on, but my only guess is that heaps of air got sucked in when that hose came off and it boiled the water, or the radiator has a blockage. And at the very worst there is an internal engine problem. If anyone has any cool ideas of where else I could look that would be great.

Things I have done:
-Replaced all the hoses (Were all leaking originally)
-Thermostat (Replaced with Genuine Subaru Thermostat)
-Flushed the engine and Radiator

Any chance that a bad cap could cause this as well?

Thanks for the reply Eric,
I too think this may be a head gasket issue. If I may ask your opinion.. is it easy enough to pull the engine and leave the gearbox behind? As it looks as though by removing the radiator and fans that if you loosen the gearbox from the engine it will just come forward and out. Anyway before I go this far, like you say I will do a compression test first and few other small bits.

Will keep you guys posted.

Cheers!

OK – An update for those interested. After having stripped the Subaru engine down I have now finished the re build. I removed all the valves and had both heads skimmed. Once they came back they looked pretty nice.. Anyway I assembled those with new valve seals, cleaned up the valves and lapped them in. I ended up buying brand new head bolts to save the risk of breaking the old ones, so the heads bolted up nicely with the new three layer gaskets. (Definitely much more durable compared to the old gaskets). Obviously I also replaced the cam seals, crank seal etc. New waterpump & Cambelt – (FYI: If you buy a Gates brand Timing belt, they give you marks on it to help you line it up. Very useful for the DOHC engine as there are about 5 marks to line up overall, and there is no way to get it wrong) Then after that it was basically do the sump gasket and small things like that, and throw it back in the car. I got around to starting it the other night and have been driving it around the pass few days with no overheating. I can call this case closed!!

I have attached some pictures below for future reference:

This is how the old gaskets looked when I first removed the heads

I actually came across this, and the flexplate had cracked around the bolt holes, this ended up being the knocking noise I could hear.

My valve storage, didn’t fancy dropping them everywhere…

FYI: Leave the torque converter behind as it’s a time consuming process to get it back in…

Preeeeeeety heads 😀

Unfortunately in this photo I had moved the timing marks, so cannot point out the marks they give you on the belt

Closer shot

Thanks for all the great help!