87laredoxj

When I checked it this morning it was not full

CrawlerXJ

Pull thermostat out, drill one 1/8" hole in the t-stat, reinstall. Problem solved.

djb383

If the rad is not full (cold motor), then the recovery system/rad cap are not functioning correctly.

That may bleed some air but since the OP is overheating, one would presume the stat is wide open thus bleeding the system quite thoroughly. Kinda sounds like coolant is entering the bottle when hot but not returning to the rad when the motor cools, thus causing a low coolant situation which in turn will cause overheating. Not sure how drilling a hole in the stat will solve the possible problem of coolant not returning to the rad (low coolant).

87laredoxj

Well just put a new rad cap on I'm just confused on this system

djb383

Here's how a open system works. The components are a 2way valve radiator cap and a non-pressurized bottle that fills/empties from the bottom via a tube connecting the bottle and radiator. When the motor heats up, coolant expands and when the rad cap pressure rating is reached (expanding coolant) the rad cap will release coolant (and air if present) to the recovery bottle (presuming the cooling system is full of coolant as it should be). Coolant will beheld in the bottle and any air that went with the coolant into the bottle rises/escapes. When the motor cools, coolant contracts and the rad cap allows coolant (no air) to return to the radiator from the bottle. If all of the coolant is removed from the bottle as the motor continues to cool, then air gets sucked into the rad. The cooling system absolutely must be completely sealed, both coolant and air tight (absolutely no leaks anywhere) in order for the open system to function correctly. The recovery bottle IS NOT sealed air tight in an open system. The bottle IS sealed air tight in a closed system.

An open system is a little trickier than a closed system. Is an open system any better than a closed system or will a open system allow the motor to run cooler than a closed system?......NO to both questions.

87laredoxj

Thanks for that. It explained it better. I've always kept fluid full but what is getting me the bottle could be at the full level and rad too but after a while the fluid is disappearing? No leaks anywhere

djb383

That could mean a leaky heater core or bad head gasket or even a cracked head. Might want to have the cooling system pressure checked for starters.

87laredoxj

Well picking up gasket set tomorrow and installing Friday (hopefully) then flushing everything as well

CrawlerXJ

Since it's the internet and your post is a theory (you can't see it in person), neither of us know. Right? Overheating is subjective. I didn't see (and may have missed) what temps he/she is running.

Sorry you took the time to write/reply.

87laredoxj

Well changed headgasket and have to do it again and put a new head on it. It's cracked which I've never seen with a cast head.