Pontiac Repair: Pontiac Trans sport heaterproblem, pontiac trans sport, temp guage

Question
Hi Todd, I have a 1996 Pontiac Transport 3.4 which was running fine until the other day when the low coolant light came on.I topped up the coolant, then the temp. guage would go up and down and I lost heat from the heater. the fan works but no heat. I had new thermostat put in and its still the same. I have spent hours bleeding air from the bleed valve near the therostat as I thaught it may be an airlock, but air comes out in spits and spurts and still temp. goes up and down and no heat.


Answer
Hi Tony:

well first off why was the coolant low what's leaking? how hot did this get? if it ran low enough on coolant and got hot enough it may have caused some engine damage like a blowen head gasket that wor explain the abnormal amount of air in the system and the temp gauge dacning all over. was cool pressure test done on this? It could be just a case of the system being bound up with air these are hard to bleed the air out of being that the engine is higher up then the radiator. Did you bleed the air out at the heater bypass pipe above the water pump as well??? if bleeding it didn't/isn't working then I would have a pressure test done and maybe a cylinder leak down test as well. if a head gasket is blown or leaking it would show up on a leak down test if the fire ring on the head gasket is gone where the combustion is leaking into the cooling system. Just a few places to start.. good luck :)