Rad/cooling problem.

[bjl95mustang]

OK, my car has been wanting to run on the hot side and I pressure tested it this afternoon and I got this.

Pumping the system up to 20psi it loses about 5 psi after 5-10 min. And with no psi on the system and the car running it only gets to about 5psi on the gauge. While running I pump it to 17-20 psi and it slowly drops. I don't see any signs of water in the oil so I'm thinking head gasket. With the engine running the psi should rise right if everything was in order?

 

[sociopath5.0]

Check the radiator cap, and maybe have it pressure tested, or buy a replacement. It could be a HG, but when mine started to go, it pressurized the cooling system, instead of showing pressure loss. I would check the cap first and move on from there if it's not the problem.

 

[bjl95mustang]

I dont have the cap on when the gauge is installed.

 

[sociopath5.0]

Well I guess I must have taken a double dose of ignorant pills this morning. I dont know what I was thinking. HG seems likely, but like I said with my experience, the opposite happened to me. I still have alot to learn, so its definitely possible. No leaks anywhere else? I hate to say it but it sounds like the head gasket. Good luck.

 

[bjl95mustang]

My main question is how much should the pressure fluctuate with the cap on? Should it hold at 16 lb at operating temp? or will it go from 10-16 depending rpm's? This is something I have no idea on.