Anyone konow the reason for this?

[Cade93TA]

My coolant overflow tank is boiling every time I turn off my car.
I keep loosing coolant that way.

For some reason it is connected to me using my A/C. I noticed last time I flushed, filled and bleed coolant system, that when I would turn on the A/C (pressure cap off the radiator) the coolant would immediately start rising and flowing out of the radiator.
What does the A/C have to do with the coolant system besides putting more strain on the engine?

BTW, if you reverse flush a reverse cooled system, do they negate each other?


Thanks
Cade

[Joe 1320]

Possible causes are a breach in the cooling system, trapped air or a partially blown head gasket. in all cases, the coolant cannot pressurize properly and the boiling point of the coolant is lowered. Also, as fluid expands it is forced into the expansion tank. As the system cools, the fluid contracts and if the system is sealed properly, fluid returns back to the radiator. If there is a breach, the radiator level doesn't stay filled. I would make sure air has been properly bled off and do a cooling system pressure check. I hope it's not a head gasket.

[Injuneer]

You might also want to check the radiator cap for pressure capability. If it won't hold the required 16-18psi, its going to allow coolant to boil as the heat soak from the engine enters the coolant at shutdown, and the volume starts to expand. If the cap can't hold the pressure, its going to allow the coolant to boil, particularly at localized hot spots, and the rapid expansion of the boiling coolant will blow it out of the weakened cap.

[Cade93TA]

Thanks guys the explanation seems to fit. I cannot find a leak, but that doesnt mean its not there. I will pressure check the coolant system and see. How do I check for a blown head gasket if it isnt turning my oil into a milkshake? Pressure test the cylinders?

You might also want to check the radiator cap for pressure capability.

I just bought a new one from O'riellys. What does pressure capability mean? Did I get the wrong pressure cap?

Thanks so much guys, now I have a direction to start looking.

Cade

[94 formula]

Whenever a liquid is heated it has a point that it will boil. If you place that liquid under pressure the temperature in which it boils increases in accordance to the pressure. Think of a pressure cooker. If your system has a leak in bad cap, head gasket, air in the line, ect. then your coolant will begin to boil at a lower temp. Do you have a fan switch or tuning and a lower temperature thermostat or is it stock? I had the same problem and it was from me not being patient enough while bleeding the system and still having a pocket of air in there. I wouldn't worry about the head gasket yet if you don't see it in the oil but did you get a new cap before or after you noticed it boiling over? Also when was the last time the system was flushed. Try bleeding it out that was my problem.

[Cade93TA]

The cap was one of the purchases to solve this overheating problem this summer. The coolant boiling is what I have narrowed it down too. I have installed a manual fan switch, 160 thermostat; Reverse flushed twice, and of course bleeding twice. THe last time I spent at least 30 min letting the car run to bleed the system. THis seemed to have solved it temporarily, but went back to boiling. And it seems to get worse when I use the A/C.

Cade

[94 formula]

The only link of the AC to the cooling system that I know of is the one fan kicks on when the AC's turned on. Also I forgot to mention when I did mine part of my problem was when I filled the radiator with coolant I was overfilling it and causing a lot of coolant to go back into the overflow bottle. I didn't realize that until I bled it out again. I just solved that by filling up the coolant then when I was done with bleeding and everything else I just siphoned it out of the overflow then filled it back up till it was at the right level on the dipstick. Have you checked for leaking hoses or anything else small that might get missed at first?

[Cade93TA]

So did you just fill it to just where you could see the coolant below the neck of the radiator? then opened the bleed screws, start engine, run heater...etc? How did you siphon the fluid out of the reservoir tank?; out of the neck of reservoir, or out of the hole where the reservoir connects to the radiator neck? As for leaks, I looked but couldn't find any. In fact over the past year I have replaced all of my tubes, including the water pump.

This is giving me some hope.

Cade

[94 formula]

To get it out of the resivour tank I just stuck a long rubber hose down in it. You could also just take the hose off the bottom of it doesn't really matter. For my car I just added coolant till it stopped taking more which takes a long time. After that I started the car opened the bleaders and left it run for about 5 minutes. I then took the radiator cap back off filled the radiator back up and kept repeating till coolant came out the bleeder screws and it wasn't sucking more in. I then syphoned the excess coolant from the overflow bottle and just put it up to the level it should be on the dipstick.

[Cade93TA]

Awsome, Thanks , Ill try that


Cade

[sidestepkid23]

my problem is similar to this one. but my fluid is backing ionto the resivor. ive tried to bleed it out and it has not helped

[sidestepkid23]

i have a 93 v6 3.4