2004 Pontiac Montana, Slight overheating and no heat from vents

Luke Smockum

Asked by Nov 04, 2015 at 12:06 AM about the 2004 Pontiac Montana Base Extended

Question type: Maintenance & Repair

So this is my list of misadventures with this " wonderful " General Motors
product. When I got the van it ran perfect, blew hot air through the vents
and did not overheat once, but since then I have replaced in less than a
week the alternator, air conditioning compressor and battery, then the same
day after that repair I made, the van decided to overheat and piss out
antifreeze out of the overflow tank, before I replaced the radiator I did put a
rislone stop leak with those pills inside the rad to stop a pin hole leak in it.
But eventually replaced the thermostat and radiator two days later, I spent
hours cafefully bleeding the system through the thermostat housing and
water pump screws..bleed til nothing was left, even did it through venting
the rad cap and eventually without it on and now the vehicle will slightly
overheat, fans kick on which is good news. No heat through the vents, no
odor, oil is not milky and the exhaust doesn't smell sweet and isn't white..
Rad hoses and pressurized keep a hot temperature to them, the one heater
core line gets hot but the outlet sometimes does, but the motor doesn't
whine or clunk or anything else.. sounds normal and the rpms are perfect.
Running out of patience and time.. anyone have an answer ? Only has 224
thousand kilometers.

3 Answers


Alright then, you still have air pockets in the cooling system. Proper bleeding is done by starting the vehicle with the radiator cap off, and let warm up until operating temp. (thermostat opening) Do not be revving the engine up as you will get a shower! You can but very slowly to help in the circulation. You may have coolant pushed out of the radiator but this would be the air pockets working itself out. Keep filling with coolant as necessary once warmed up and air has pushed out, Put the radiator cap on when running once done. If you shut the motor off before installing the radiator cap. it will over flow out the radiator.


To be clear, refill as necessary when the thermostat is opening up, you will see the coolant level drop each time when the thermostat opens, until full.


These GM cars are also famous for defective lower intake gaskets. It can be difficult to see where the coolant is coming from, but I would consider this a possibility as well.

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