Cooling system not pressurizing

[JPERL]

I noticed I can open my radiator cap when the engine is hot and there is no expulsion of fluid under pressure however it seems all the pressure is being released into the reservoir because I turn the engine off and the reservoir tank overflows.

I have tried different caps with same result. Could the filler neck for the radiator cap be bad?

[blakebecker37130]

Did you try a new cap with the correct pressure rating? I had a similar issue and it was the rubber seal on the cap. It was deformed and cracked allowing the coolant to dump into the overflow tank. Also check the filler neck for corrosion, it a long shot but could be obstructing the cap function?

Regards,
Blake

[JPERL]

is cleaning the filler neck with sand paper advisable to remove the corrosion

[blakebecker37130]

is cleaning the filler neck with sand paper advisable to remove the corrosion

If it’s real bad, that may work? I would utilize rubbergloves, pink stinky rust remover naval jelly and steel wool to get the neckreally clean and buffed. If it’s minor corrosion run a green scotch bright padaround the internal area of the filler neck. You may have to or wish to flushthe cooling system after any scuffing around in this area to evacuate any particlesthat get dislodged or introduced to the system. Check the overflow outlet tomake sure you don’t plug it up in the process. Did you find a lot of corrosion?My 87 had a significant amount. I chalked it up to the previous owner runningmostly water and most likely tap water in place of coolant. When I drained itthe fluid came out oxide orange/red and smelled pretty much like rusty water.No sweet glycol coolant smell detected. My filler neck had light corrosion butnot impeding anything, so while I was flushing it I stuck a green scotch brightpad in the filler neck and rotated it around to remove the corrosion. Icontinued flushing the system until clear water came out for an extended period.I thought the radiator and heater core were toasted, but currently the vanstays cool and makes good heat. Hope this info helps.

Best regards,
Blake