Expert: Roland Finston - 8/3/2011

Question
Why does my 300m spill out coolant after I run the air? I just replaced the radiator.

Answer
Hi Hope,
The demand on the cooling system is of course increased by the air conditioning. Does the temp gauge stay in the normal range while you are using the a/c and driving around? If so, then I wonder whether there might be some air trapped in the system which might expand immediately after you shut the car down. There is a bleed valve near the thermostat housing which should be opened when the system is being refilled and then closed when the coolant levels reaches to that level and has an opportunity as well to drain out a bit more through a hose on the valve for collection and reuse so as to be sure to drive out any air via that pathway. Squeee the top radiator hose at that point as well to push any air in it out. Then stop adding fluid/collecting fluid from the drain hose and finally you close the bleed valve and fill up the system  until the level in the pressure bottle is reached as indicated on its side. The pressure cap on that bottle might also be leaking so take a look at its gasket. Ask whoever replaced the radiator to recheck the refilling procdure to be sure there is no air trapped in it. It is also necessary to pinch the side hose of the filler bottle while adding coolant to the system as there are two chambers in the bottle and you want the overflow chamber to be empty when you are done. Then remove the clamp on that hose. It may be that the bottle wasn't set up properly.
Let me know if you want the written instructions on these points and I can copy them off a CD and email them to you. But I need to know your email address, send it to me via a 'private option' follow-up question.
Roland