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Pontiac Repair/1998 Montana coolant fill procedure

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Question
Hi Todd. My daughter has a 1998 Montana, 3.4L that started overheating a few days ago. I replaced the thermostat since that's such an easy job (NOT!) but that didn't help. I decided to replace the water pump so I drained the radiator and replaced the pump. The old one looked good when I removed it but I replaced it anyway. To refill the coolant, I cracked open the bleeder above the water pump and filled the radiator until coolant came out the bleeder. I closed the bleeder, replaced the radiator cap and ran the engine until the thermostat opened. I then opened the bleeder valve on the thermostat housing until mostly coolant came out. The engine overheated quite rapidly. Both radiator fans came on. I think I might have air in the system. Do you have the correct coolant refill procedure? I also rented a cooling system pressure tester from the parts store. I pumped it up to about 13 PSI and it dropped down to 12 in about 5 minutes. I'm also suspecting a lower intake or head gasket issue since I don't see any visible leaks. I don't see any coolant on the oil dipstick but I haven't drained the oil to do a closer inspection. Also,there's no heat coming out of the heater, front or rear. Sorry for the long message but I thought you should know everything I've tried. Thanks!

Answer
Hi Dan.
Bad news if you over heated this it more then likely blew a head gasket. more then likely the lower intake has been leaking for a while and ran low on coolant and then it over heated. causing a head gasket failure see that cycle all the time on those vans. you have the bleeding down right but it's more then likely getting compression from a blown gasket into the cooling system which is causing your rapid increase in pressure.  

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Todd Puccio

Expertise

General auto repair,electrical issues,driveability issues,anti-lock brakes,SIR systems,HVAC,engine performance,Gm specific. I have worked at my current dealership since the 1990 model year anything much older than that I have limited exposure to. I do not have very much transmission experience so those question you may want to ask of another expert. When you send me a question let me know the exact make/model/engine and year for the car or suv you have it makes it easier to answer the questions that way. If your happy with the answer I gave you please feel free to Donate. This is a free service to you and I am not compensated at all by this web site. I have 22 years of experience to share with you and my knowledge wasn't free to me. I had to pay for my education.

Experience

Experience in the area: I have been a technician in GM dealerships for over 22 years and I am a ASE master technician. I work at a Buick and GMC truck store Previously I worked at a Pontiac GMC store for 18 years. I Served a a lead technician when dealership was on a team system. I just recently moved to a Buick,Hummer,Saab Store when my franchise was purchased by this dealership. Organizations: ASE master technician

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ASE

Education/Credentials
Education/Credentials:High school diploma,2 year vocational school degree 2 year college degree. Associates degree in applied sciences (auto technology)Awards and Honors: GMC master technician

Awards and Honors
Master GMC truck technician Master ASE technician in 9 categories

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