Question for you guys, I’ve been having an issue with my h3t alpha where my coolant will start overflowing when I park and or shut off my engine. Already changed the thermostat (aired it out). ObdII says it’s at 208° while running and climbs to 218° when i shut it off (heat sink I assume). Anyway do you guys think it’s a bad radiator cap or bad water pump?( Water pump doesn’t seem to be leaking) When I look at it when it’s cold it’s well below the fill line in the reservoir so I assume it’s not over filled.

 

Where is it overflowing from? The cap or the reservoir? Do you smell coolant while driving? My guess is you have a leak and H3 radiators are no strangers to Mr. Leak.

At hose temps it should never occur so I would suggest you check the quality of the coolant and make sure it is in the correct mix 50/50 coolant/water. Too much water and you can easily get what you have going on.
If not sure, drain and refill with fresh Dex Cool 50/50.

Before doing anything else, drive it to hot, stop and shut it off, open hood and observe.

 

Air in the system, blockage, thermostat stuck closed, defective cap, head gasket,etc. As Doc stated, open hood and observe. Coolant in overflow boiling, radiator hose collapsed, coolant leaking, etc....

 

It’s leaking from the reservoir when I stop. Already changed out the thermostat and now the radiator cap and there it went again. Got home from work and started overflowing while it sat idling. Water pump pully isn’t leaking or making noise. Oil looks normal no water making it look milky To point towards a head gasket. I’m stumped, thanks for the reply’s guys

 

How long has it been since the t-stat change?
Have you pressure tested the radiator?
Have you pulled the H3 up on car ramps and left the radiator cap off to let air purge?

 

changed the thermostat about a month ago and the no haven’t pressure tested the radiator, I’ll try purging it again tomorrow maybe I didn’t get it all out after changing the thermostat. Thanks for the reply’s I appreciate it guys

 

run your heat when purging. its possible you have air trapped in the heater core.

 

Yeah I tried, so I got a block tester with the color changing liquid to see if exhaust gasses come up and nope but I can hear the coolant going into the reservoir when I’m going over 40 mph but I won’t do it at idle or when I accelerate when I’m parked

 

make sure you have 50/50 coolant because if it is mostly water it will expand, boil and steam off way before 50/50 mix would.

 

Yeah I checked the mixture with a tester. Really hoping it’s not a small leak in the head gasket but there’s No water in oil or oil in coolant or white smoke in exhaust or exhaust in the coolant so I’m here tearing my hair out lol