[pcv]

I think you may have a bad head gasket.
Remove the spark plugs and look at them. Are they whitish? If so, that cylinder has coolant leaking into it. With the plugs off, pressure test the cooling system and and after a while look inside the cylinders for coolant or crank the engine ( stay away from the plug openings, unless you want to have a shower) and watch for coolant spray.
What is happening in your case is the compression from the cylinder is leaking into the cooling system and blowing it into the resorvoir.