Headgasket

[liger86]

can someone tell me what are the signs of a blown headgasket, I read about white smoke but where should it be comming from if the HG is bad etc.

[gto7419]

Blown headgasket could smoke from under the hood, oil leak under the hood, blue/white smoke out of the tail pipe, milky residue on the dipstick or oil cap, etc... There are lots of signs - depending on if the headgasket blew from inside to out, or just inside...

Danny

[isotopeman]

Compression tests can be quick and useful as well.

[bny82]

Also another sign is the coolant reservoir slowly over filling.
My dad's has that problem and i will be doing the gaskets soon, it didn't even show up in dye and compression testing as it is such a small leak

[evolutionmovement]

I don't think I've ever seen a blown HG in a Subaru smoke or have oil/antifreeze mixed. Check for air in the radiator while it's running (do this cold of course). Overheating with a good thermostat and a non-weeping water pump is also a sign. They usually seem to go at the fire ring, getting combustion gases into the antifreeze. You could also have someone check the coolant for hydrocarbons.

Sometimes what happens is it will overheat gradually on the highway, but may be cool in the city for a while before it just heats up all the time. What I believe happens is combustion gases build up in the water pump impeller pocket when the impeller moves at a relatively constant speed, gradually reducing pumping efficiency as coolant is displaced. The constant change of impeller speed in the city resists this by not giving the gases a steady environment to build up.