Ok for all you super smart motor heads here is the problem. 1997 Olds 3.4l minivan. Overheated on my daughter, I replaced the the thermostat, waterpump and radiator cap. Then flushed the system, refilled and ran it in the driveway for 30 minutes or so. It would not overheat. This morning my daughter heads to school and it overheated again. The thermostat never opened because the heater was blowing cold air. I opened the bleeder screw above the thermostat and drained air for a while. Once the system was out of pressure (overflow tank was full now too) I was able to drive home, wathching the thermostat cycle via the temp gauge....heat up, cool down. I got home rebleed the system, topped it off with coolant and could not get it to overheat. I let the van sit all day and get nice and cool, whent for a drive and it overheated again. I stopped bleed off the pressure again (overflow full again) and was then able to drive all around. I was thinking head gasket, but it does not rebuild the pressure. Could it just be improperly bleed and still have some residule air in the system. I am at a loss and any ideas would be appreciated.

Shane

Ok for all you super smart motor heads here is the problem. 1997 Olds 3.4l minivan. Overheated on my daughter, I replaced the the thermostat, waterpump and radiator cap. Then flushed the system, refilled and ran it in the driveway for 30 minutes or so. It would not overheat. This morning my daughter heads to school and it overheated again. The thermostat never opened because the heater was blowing cold air. I opened the bleeder screw above the thermostat and drained air for a while. Once the system was out of pressure (overflow tank was full now too) I was able to drive home, wathching the thermostat cycle via the temp gauge....heat up, cool down. I got home rebleed the system, topped it off with coolant and could not get it to overheat. I let the van sit all day and get nice and cool, whent for a drive and it overheated again. I stopped bleed off the pressure again (overflow full again) and was then able to drive all around. I was thinking head gasket, but it does not rebuild the pressure. Could it just be improperly bleed and still have some residule air in the system. I am at a loss and any ideas would be appreciated.

Shane





I think the problem is with manifold gasket.

Headgasket, not uncommon for a GM 60-degree V6's. It's pushing combustion gasses into the cooling system. You could have a shop confirm with a hydrocarbon sniffer test for probably around an hours labor charge. It's a fluid that changes color when exposed to combustion gasses.

engine normally wont overheat unless underload, going down road cylinder pressure will be higher and push past gasket. gm had intake and head gasket problems, part was related to antifreeze gm used.