I have a 2001 Pontiac Grand Prix SE with the 3.1 and 170xxx Miles. got it around 150xxx.
Going to give some background info before jumping into the problem, skip ahead if you just want the current problem
The car has had the headgaskets replaced with felpro gaskets and the transmission rebuilt and replaced by me in the past year. I had a mechanic friend who helped with some parts of this mainly the rebuild portion of the heads and gaskets. Im an Avid Do it yourselfer and not a professional by all means.
after replacing the headgasket the coolant temperature would still randomly get hot while driving and there would be air bubbles. in the coolant. I ended up taking a shot in the dark and fixing this by replacing the overflow tank and the hose going to the filler neck with a junkyard part. Not sure why this fixed it but no longer would the car spike up to 210-230 degrees while driving it. I also bled the coolant after doing this.
So the car was functional and I drove it around and still do to this day after those repairs. The problem is the car will rise in coolant temperature during idle or slow traffic (30mph or less). It will rise above 210 and go to boiling and touched the redline for just a second on one occasion.
I am tired of having to look at the gauge every 10 seconds while driving this car. so heres what I have done to troubleshoot.
The Problem and The troubleshooting I have done.
So the problem has been the car will rise to near boiling while idle for 5-10 minutes, the fans do not kick on and after I messed with it and tried to bleed it yesterday it got up to 210 while driving but it used to stay around 180 while driving.
Now If I am driving on the expressway or 55 mph+ and getting good airflow. The car will not overheat and stays around 160-195. when I start to idle the car after a few minutes it starts to rise and will continue to do so until I get the car moving.
Apparently the cooling fans come on at 225 coolant temperature when the ECU sees 225. I have a live data scanner and idled the car up to 225 per the ecu It was a little bit higher on the gauge near boiling but when it hit 225 on the ecu I saw fans kick on, It cooled it down to like 200-215 and it seemed to be operating as intended. didn't go to redline or anything.
Recently The car will get hot, Fans do not kick on and the ECU and gauges are reading differently. There are times when I look at the gauge and its roughly 230-240 and my scanner says 80 degrees. Today It was up at 210 and my scanner said 160. The fans are not kicking on and I believe its because the ECU is not seeing the high temperature. So I am not sure if the ECU and the gauges pull from seperate areas or what causes the difference in temperature.
I have opened the bleeders when its hot and bubbles and a kind of steamy coolant comes out. So I do believe the coolant is getting hot. I went to bleed it yesterday, Popped the radiator cap, Topped up the nearly dry overflow Reservoir and started the car. The coolant was just a bit low but still visible in the filler neck. I turned the heat and fan on high (only setting that works) and the gauges and ecu both stayed around 185. waited for what seemed like forever and it was not getting hot. so I turned the fan off. The car started to warm up. and bubble. I thought their was just air the system and was pretty happy thinking I solved the problem. But it kept bubbling and bubbling and bubbling, almost like when it had a blown headgasket, i had to keep topping it off and the reservoir to the point that it was obvious that there wasnt that much air trapped in the system, I mean I bled it for maybe 5-10 minutes straight of it bubbling hard, if there was that much air it would have overheated while driving on the expressway I feel.
https://streamable.com/fuydq <-- Video of what happened toward the end of me bleeding it. I bubbled alot for quite awhile and then bubbled and steamed bad as seen in the video.
IT started steaming and throwing coolant almost puking it up, temp gauge was high and ECU was reporting 200 so no fans were kicking on, I shut the car off and decided I was just going to top off the filler neck and drive it and see what it did, I only had water to top it off, so I filled it up to top, It kept bubbling slowly and the level kept going down I did this with about a gallon and a half of water. The level kept dropping, and when the level would rise It was straight water, So I don't know why it wasn't mixing with the coolant or where the water was going. I also filled the overflow tank twice and it drained during this time,
I checked my oil and its not mixing there.
What I think it might be
I am at my wits end. The car is technically driveable but I don't want the headgasket to blow again, I checked the radiator and all 4 corners and the middle of it is hot so I dont think Its a plugged radiator.
I get good heat so I dont think its a water pump issue or completely full of air.
WHen the headgasket blew, I would have a Ton of air in the system, No heat due to air and it would heat up no matter if I was driving or idle, So I do not think it is a blown headgasket, Or atleast not a badly blown one.
Obviously the fans are not working and that is contributing to the problem, but I think thats because the ECU is never reading 225, Because when I checked it a few months ago and the ECU saw 225 the fans kicked on and I thought I didn't have a problem.
So I think I either have a small leak that is letting air in that is bubbling, I thought maybe somewhere near the filler neck because the level only drops into the neck just wont stay topped off, But I dont see any leaks there, Maybe there is an exhasust leak that is letting air into the cooling system?
Or I am running Universal green and not dexcool. I do not know the exact mixture, is it possible that the coolant mixture is getting too hot and steaming and bubbling and thats where my issue lies?
Sorry for the Light novel on my car, Im sure its all over the place and formatted poorly, I am just trying to get all the information down.
