So i have a 98 impreza 2.2 i bought the car with an over heating problem i changed the thermostat the radiator cap, hoses, changed the oil i did the blue devil head gasket sealer everything except the water pump and the timing belt which im going to do tomorrow heres whats happening right now the car still over heats but the temp needle bounces pretty quick from cold to hot then back to cold i have white smoke coming from where the down pipe meets the the cat but no smoke nor water coming from the muffler tip my coolant resevoir has a small constant bubble when i take the car for a test drive it overflows from the coolant resevoir, i attempted to take the therm out and it still over heats, i notice shiny metal material in the coolant a long with small oil puddles in it im not sure if its from the radiator leak seal the 1st owner had put in it or if its from the water pump if anyone has any information please let me know im running out of options... And the oil dipstick has no oil on it when i check it even though i just did an oil change yesterday

 

Blown Head Gasket.

 

I'm sorry ,but it sounds like a bad headgasket to me, it happened to my 2007 STi a couple months ago.
You might want to flush your coolant too..

 

especially b/c the oil mixed with the coolant

 

At this point your better off completely replacing the whole engine, literally.

 

Sounds like the head gaskets are beyond repairable through liquid stop leak solutions. You need to either have a full headgasket rebuild job with head machining, or buy a healther 2.2 and just direct swap it.

 

How much is it to do a head gasket? And do you guys think blue devil head gasket sealent will work?

 

Your looking at least 1k to do the head gasket. No Head Gasket sealant will work.

 

Alright thanks!