Rad overfill cap gaining pressure and blowing off

My dad bought this car for 2 grand great shape but it seems like it is always doing this, i would love to do a search but i work in 20 mins and i need to hopefully have answers by the time i get home is 01 3.1L malibu. whnever it runs it goes great(no overheating), but when at idle will just shoot the rad cap off on the overfill and some pressure is getting in there, can the rad stuff cehvy causes that or is it air?? or what, i need some help i know absolutely nothing about chevvies, any help appreciated:wink:

Ok First When the car is complete cold check if you have the antifreeze only where it says full line do not go pass it. Second if it on the full line then turn the car on and the heater full speed for about 5 min. or when the car reaches the normal temp. turn the car off. Know look where the water pump is there is a line thats runs from the container of the antifreeze to the top of the water pump. There is a nut in which you open little by little in which if you hear or see bubble it cause it had air wait until you don't hear and more bubble or see no bubble when antifreeze only comes out then retight the nut. Now if it still does these poping or the top. Try this also this will help a lot. In order for this not to happen you do need to have the ac on so that the whole system curculates ones you use more the ac the poping of the cap will not happen. And trust me this was happening to me and i have to change about 4 caps.

hey, i'll do that first thing in the morning when i wake, thanks for the help man, appreciated

hey, i'll do that first thing in the morning when i wake, thanks for the help man, appreciated

Man if it's blowing the radiator cap off of it, you've got a bad radiator cap or a bad reservoir or both because of stripped threads. You've either got stripped threads on your cap, or the reservoir, or both.

are can a bad rad cap cause pressure???? bcuz its blowing the antifreeze out to.

are can a bad rad cap cause pressure???? bcuz its blowing the antifreeze out to.


I'd replace the radiator cap if it were me.

Another thing if all what I said does not work trying sending the raditator to get flush out maybe one of the lines are clog

with the car cold open the radiator and look at the level if it is low that is you problem as the water circulates it is under pressure so if the radiator is low that pressure could be passed to the air in the raiator the air gets much hotter than the water causing it to rise to the highest point possible (overflow tank) and building pressure so fill the radiator directly not by the overflow

Well, In my case even if the level was at it level it should be it will still do the same it wasn't low or high it was where the line say full when cold