Okay so I got a car, a 98 Lumina, no warranty, ran fine the day I got it.
Next day, it was overheating like crazy, within seconds [literally] the temp gauge would go from normal to HOT.

Eventually I took it to the garage I used to take my Bonneville to.
They replaced the Thermostat and flushed the coolant.

So, then they test drive it and the engine blows.

Dealer says they'll put new intake manifold gaskets on it.
They put them on, change oil a few times, replace coolant, and i pick it up.

I drive home today, it runs fine, runs normal temperature, feels like it did the day I got it.
Then, later today, it starts overheating. Again. I look under the hood, and there'* coolant all over the place by the overflow. I could see little bubbles in it too.

I checked the oil, there'* no coolant in there from what I can tell, so I don't think it'* the head gaskets.. What else could it be?

I've heard things ranging from a simple overflow cap replacement to bad gaskets. This car is a nightmare, i've never been more in my life. Any ideas on how I can at least troubleshoot this problem?

I had this on Chevrolet Forum with no replies, so I came back. This forum seems to be like 300% more helpful

Unfortunately alot of things could be going on. Is the fan operating and cycling? Any steam coming out the exhaust? Radiator in decent shape and clean? Do you see coolant moving with cap off and coming up to temp?. Seems most of these questions of course would be obvious to a tech. Bad water pump seems a likely culprit, but itz hard to say just sitting here.

Check your fan, does it turn freely or does it turn rough? Check the inside of your oil cap, is there any yellowish semi solid junk inside? The 3100 is famous for blowing head gaskets, my '95 Grand Am GT went through two sets. I put a 3400 from an '02 GA in and it solved all problems and gave me more than 50hp

Also could be air pockets in the coolant system.

They may not have properly burped the coolant system when they refilled the radiator and motor.

You may just need to burp it yourself. Or take it back to the dealer right away.

I can't take it back to the dealer.
Last time they had the car for over 2 weeks.
They wouldn't call us back or anything, and it was too far to drive to.

How would I burp the system? I heard there'* a bleeder screw on the water pump but I couldn't find it.

I thought it was air too; I think my head gaskets are fine, because I can't see any milky stuff in the oil.

Also, how do you get the radiator cap off? I can turn it, but it won't come off? The one on my bonneville came off real easy..

Follow the blue line to the bleeder screw location:

TShoseandTSbypass.jpg

Not knowing the condition of your motor you may or may not want to try this below. Therefore I'm not responsible for any outcome that may or may not happen at this point.


As for taking off the radiator cap all you have to do is push down and turn counter clockwise.


How to burp your system:
When you feel all the air bubbles are out of the system, close everything up and let the system cool a bit.
Than go back out to the car and do not open the radiator cap.
Find the bleeder screw on the thermostat housing.
Start the car and slowly open the bleeder screw.
You will see a small stream of coolant come out.
If there is any air left in the system it will spit out air through this bleeder screw.
Close the bleeder screw for a few moments than repeat a few times until just coolant comes out.

Let us know how it all turns out!

Thanks for that info, i'll see if I can do that tomorrow
Bad weather today, and I have no garage :[

But I also might have someone check the radiator out. I think it may be getting clogged somehow, because I noticed a little residue in the radiator reservoir that'* probably from when the previous owner used DexCool, and I assume the same sediment could be in the radiator.

My only problem is, the temperature fluctuates. It runs normal, then heats up QUICKLY, then cools down QUICKLY or stays so hot that the coolant boils over. I noticed it heats up quicker when I go uphill, and cools down very fast downhill. I can't think of any explanation for this.. Any thoughts?

I had a 95 Olds with a 3100 about 7 years ago that overheated and blew a head gasket. Turns out that when the dealer replaced the water pump and head gaskets they did not properly burp the system of air. The motor was acting just like yours. The gauge would go up than down really fast. Sometimes stay hot than other times I would have no heat because of the air pockets.

So what you are describing is what I went through.

I still believe that there is just air pockets in your radiator.

The best thing you can do at this point is start with bleeding the system down of air.

I agree with Toddster, start with bleeding the system. Youre gaining heat uphill because of the strain on the engine and losing it downhill because no strain and plenty of air. Let us know what you find, good luck

Thanks. Nobody could tell me that, I kept asking if there could be air in the system because I had bubbles in the coolant but no coolant in my oil. They kept saying it'* gotta be gaskets. I got them replaced, and it'* still messed up! I had a new thermostat and three coolant flushes too. I hope burping this works, because it'* the only car for the family and we just bought it.