2000 Oldsmobile Intrique Coolant Boiling Over and Gauge Reads Hot

This is a long shot by me and hope that you will help me. I have a 2000 Oldsmobile Intrigue. I got new and have been keeping it up since. You have probably heard of this engine running hot during the winter time ( for those of us that live in cold states) but normal in the summer and mine started a few years ago but never went over the 3/4 mark. When it first happened I went to radiator mechanics, dealerships, and even local garages. No one could tell me why but said the engine was not running hot as the coolant was not boiling. Skip to this year. Summer, car ran fine and when winter hit the temp gauge started it’s winter climb. A month ago I was checking the engine over and noticed that the water pump was leaking. I replaced the water pump and the thermostat as there was supposed to be a new one by GM that was rated for 180. I took the car to a garage do to a bleed and that is when the whole thing broke After getting it back there was a loud popping noise coming from the engine that sounded like the cooling system had air in it, the temp gauge went all the way to redline. I stopped the car and when I loosened (did not remove) the reservoir cap the coolant just bubbled up and out the over flow drain. I took it back to garage and they told me that my head gasket was blown. I took it to a dealer for a second opinion and they told me the heater core was partially plug. So, I replaced the heater core (I was a jet mechanic before an illness ended it) no small feet and did bleed myself. The popping noise stopped but the temp gauge still red lines. When it reaches red line I can begin to hear the popping noise, this time no doubt due to the heat. If I loosen the reservoir cap I still get the gush of coolant coming up but the temp gauge then drops down as does the coolant to a normal level. I have gone all over the net but nobody seems to have a straight solution to this issue with this engine. IF I keep the rpm’s up around 2700-3000 the system runs normal, just between the 1/4 mark and the 1/2 mark. I know this is a reverse flow cooling system for the engine but I cannot find any schematics on it to trouble shoot it more. Hence, going on line looking up the engine and trying to find someone or company that might have experience with this engine. This is why I am writing you. You are the first of my search and hope that you will be able to advise me on how this cooling system works. From basic research I know that fluid will flow from the reservoir to the pump to the thermostat first then to the heads and rest of body. That is all I can find. Could the thermostat be bad and causing a back pressure?

Wow that’s quite a story! I would basically want to start from scratch like you have never done any repairs to the vehicle. yes…also, I would really recommend doing a leakdown test on each cylinder to see if you do have a possible head gasket problem. You would need a special too to do that, though.

Is there some where that has the steps to trouble shooting the cooling system?

I would get the actual repair manuals for you car.

I have the Haynes or whatever the name of the book is for this car but it does not have steps to follow or schematics to use.

OK. After any testing has been done, leak checked, etc….I would fill the cooling system to the top and bleed it thoroughly. This may take hours to complete and you may go through more than two gallons of coolant. I would get the GM manuals.

Oh, those books. Any cheep place to get them?

Not that I know of. Your local dealer can order them for you.

With the bleeding, does the reservoir need to be unbolted and lifted higher than the engine? There is only one bleed port on the radiator and that did not show any bubbles but a steady stream. But it did pulse a few times.

What you need to do to properly bleed the system is to fill to the top of the reservoir, run the engine to get it hot, even hot enough that it expels some coolant from the reservoir, then top off the reservoir, install the cap tightly and shut off the engine. Let the engine cool for at least an hour or more, then you will see the coolant level drop in the reservoir, which is removing the air from the system. Top off again and repeat as often as necessary until it’s not bubbling over coolant. If you can never get it to stop bubbling over then you do have a mechanical problem in the cooling system, whether it be a bad head gasket, cracked head or block, water pump, t-stat, etc.

How long to to run the engine hot? 5 minutes?

Until it starts running hot…how ever long that takes. Depends on air temperature where you are. You want it really hot so it will suck down the level of coolant as the engine cools off. Just getting it warm is not good enough.

Thanks. Will try to make sure it is bleed well before doing anything else drastic.

Yes but before you bleed it again, do a pressure test to check for leaks and do a leakdown test to check for a head gasket problem. If those check ok, then proceed to filling and bleeding.

Thank you again !

You’re welcome, have a good night, and good luck!