coolant coming out overflow

it's normal try to replace the both caps on the tank the pressure cap which is on the side a lot of times volvos had some real problems with these caps. i dont think its a head gasket just from the material that head gasket is made from it's stainless i believe so it's almost impossible to burn it and if you had a head gasket truck me there is going to be a lot more than just a little bit of coolant coming out. might even be if you were in hot temps and the cooling system got alittle more strained down than normal.

 

You can take a pot cleaner and clean the plastic tank where caps goes on to get it to seal better?

 

it might just be slightly overfilled i guess. but yu should get it pressure tested over night and see if you are loosing pressure.

 

Sample of oil to the lab look for contamination

 

i know i know this sounds kind of obvious, are the fluids actually overfull? If not a short term solution is to grab the radiator cap turn it about 180 degrees to the left this will greatly reduce the water pressure and reduce overflow this is a technique i picked up years ago when you have a water leak it can help you get back to a repair shop with out ceasing up the motor.

 

How many times during that 600k has the coolant been serviced/flushed? And with what type? The additive package in coolant only last so long before cavitation starts eating at things. Also, it makes sense that air bubbles enter only on the power stroke. That's when the most pressure is exerted on the head/headgasket. I wouldn't be surprised if you get a slight mis-fire or rough running the first couple mins of idling on a cold engine.

 

What was problem did that fix it for good