Ok, So I bought a 1994 Volvo 850 Non turbo 5cly Auto about 6 months ago. When I bought it, it had a cracked radiator and broken odometer (both very common). I had a temporary seal put on the radiator (hasnt leaked since). It has 350,000+ miles. Just had all the fluids filled. Today when I was driving it. The Oil Pressure light would come on when idleing, but when I put the gas down it would either flash on and off, or completely go off. It was running very different that usual. I pulled up to a stop sign and it stalled. I went and opened the hood and there was so much smoke (a very light colored smoke) in the engine compartment. It was also coming out the tail pipe when I tried to crank it. It obviously would not start again. It also had a VERY loud noise coming from where you add coolent. It was also bubbling in there too. I am assuming this is not good. I am a mechanic but I have never working on one of these. I think it may be a head gasket, or maybe bad oil pump. I have no idea. Any suggestions would be great! Like I stated above, the oil is still full, Along with the coolent, so it didnt overheat or run out of oil.

 

If it was boiling then it overheated.
I would pull the spark plugs and inspect them.
I would say the headgasket blew.