Hey y'all so I've been working on my 04 gtp trying to get the cooling system clean and I've done 2 hose flushes, 2 regular distilled water with flush treatment type flushes, and was doing my 3rd just now when after running it for about 25/30 minutes and turning car off, my coolant started overflowing out of my reservoir. I've never had this happen before even when driving it more than this, and it's also never overheated on me. I did notice the upper radiator hose was super hard like a lot of pressure when the car was idling after a bit at operating temp..is that normal? I'm super worried about a possible blown head gasket, my buddy thought I could have one because he said he smells lots of gas when idling.
I just don't understand why this happened after shutting car off, and it wasn't overheating either. Any ideas here before I start a compression test?
