xwinterx

Greetings,

I have a 2004 Chevy Classic with the 2.4L 4cyl engine and about 120k miles on it. Recently on a road trip, the car suddenly overheated and left us stranded on the side of the road. When I opened the hood to see what the problem was, there was coolant everywhere. I had my father and uncle pick us up with a flatbed trailer and journey home. Today, I filled the reservoir to the appropriate "cool" line, put the cap back on and started it up to see if I could see any leakage. It ran for a good 10 or 15 minutes with no leakage. When the temperature gauge got to be about 170ish (just a little lower than it's normal running temp) coolant began spewing from the overflow hose. Before that happened, there was no pressure on the upper radiator hose. I'm assuming this is when the thermostat should have opened. My first thought is a faulty reservoir cap. I replaced the reservoir and cap about a year ago. I plan on hitting Autozone (mainly because it is the closest parts store to me) and picking up a new cap and seeing if they have a coolant pressure tool in their loan-a-tool program. Aside from a faulty cap, does anyone have any suggestions? I'm far from a pro with this or any car. I've been reading a lot about the possibility of a blown head gasket but it certainly seems odd that at about the point the thermostat should open is when I get the coolant blowing through the overflow hose. Anyone have any advice or insight? At this point, all I can think of as a good starting point is testing the cap and cooling system if I can get the tool and maybe replace the cap if I can't get the tool on loan. Both radiator fans do turn on and seem to be working. Upper radiator hose was hot with pressure on it after the blow out occurred. Based on this, how much could the reality be that it's a problem with the head gasket? Any help/suggestions is greatly appreciated!

kevinkpk

Thermostat is the first thing I'd replace

xwinterx

Thanks! I'll probably do that soon. I replaced the cap but couldn't get a pressure test loaner tool and I don't feel like spending the money on one yet. Even after replacing the cap it did the same thing. I also tried running it with the cap off and eventually it did the same thing too which started me wondering if it was the thermostat. I could hear what sounded like the water/coolant boiling so it sounds as if it isn't circulating through the system. I did have the water pump and thermostat replaced a few years ago. Today has kinda been sucky for trying to troubleshoot my car because of Easter and family functions. I didn't see any frothy or foamy or discolored oil on the dipstick but wasn't sure it I would see it there or not. I'll probably drain the oil tomorrow too to look at it since it is a couple thousand miles past needing to be done anyhow. Would an ODB2 code reader help at all? I have a friend that has one but would have to wait a couple of days until he is back in town.

xwinterx

Which hoses are the upper and lower radiator hoses because they are pretty much at the same level. I know on my CJ5 you can clearly see which is which. I believe the upper hose is located on the passenger side of the radiator and the lower is located on the driver side. Yes? I touch-tested them and the one on the passenger side was hot and the one on the driver side was barely luke warm which I attributed from radiated heat from the engine compartment. So this leads me to believe that the thermostat is probably stuck closed since it doesn't seem like the coolant is circulating. So the first thing I am going to try, like kevinkpk said, is to replace the thermostat and go from there. I hate trying to work on this car. I much prefer my 1962 Jeep CJ5 or even my 1997 Ford F350 Powerstroke diesel. So much less crap to deal with and so much more room to work!