2006 Chevy uplander we have replaced water pump thermostat and radiator cap. We have flushed the radiator and all the lines we have eliminated the heater cores both front and rear. No oil in the coolant and no coolant in the oil. The fans are working just fine. No smoke like it could be heads or head gaskets. We have burped it for several days and it will run fine at an idle for a couple hours in the drive no overheating but here's the mystery after driving for about 20 mins it will suddenly peg hot fairly quickly. And no it's not the gauge it's actually overheating. We have tried everything and still don't know what is going on. My father who is a mechanic for over 30+ years is stumped and my husband who is a mechanic for 15+ is stumped as well. Anyone have any idea what could be wrong with this damn van 😂🤣

 

How do you know that it is overheating? How long have you owned the van ? Did this problem just pop up one day ? Cooling fans turn on (running) when van overheats ?

 

Check your coolant mixture. You might have put concentrated coolant in there. it needs to be 50/50