lumina overheating

My 1997 Lumina 3.1 is overheating and I'm baffled. This is temporarily the only car between two working adults, so my situation is urgent. It overheated coming home one day. I checked the coolant. A little low, probably not enough to be a problem but I filled it anyway. Next I tested the thermostat. It was fine, but since it's hard to get at in this car I replaced it anyway to save hassle down the road. I then pulled the water pump which appeared to be fine. I replaced the radiator cap even though the one I had was only 3 months old. I took the car for a spin and it still was overheating. I kept the heat on so I could see if it was blowing hot, letting me know if the coolant was flowing properly. The temp gauge rose pretty high. At one point it dropped a little, but overall it was not cooling. There were a couple times I got warm air from the vents for a 2 second burst, but overall just cold air. I ended up having to stop for awhile to let it cool before I could even get it back home. Could this be an air pocket? If so exactly what is the procedure to fix this? The only other thing I can think of is a blockage somewhere, but how can I determine where? I flushed the radiator less than six months ago. All my money is tied up in a project car right now, so I can't afford to take this in to be fixed. Please help!

 

Sounds like a clogged heater core.

Disconnect the two heater hoses coming out of the firewall (engine side) Stick a hose in there and flush it out.

You can test if it's clogged if only one of the hoses coming from the core is hot. BOTH should be hot.

 

the radiator does most of the cooling not the heater core. although the heater core is the same as a small radiator, your car should not overheat even if your heater core is clogged. if your getting decent heat from the vent its not clogged. is your car in fact overheating? have you used a thermometer to test coolant temp after the car has warmed up?

 

Air pocket's a possiblility although I don't know that it could possibly be big enough to cause overheating. You might park nose-up on a steep incline and remove the radiator cap. Start engine and allow to warm up until the thermostat opens. You may or may not get some overflow as things start heating up. When the thermostat opens you should see some flow in the radiator and the level might drop. If there's an air pocket you should get a "burp" and level could fall significantly. If so, immediately top off and slap the cap on. See if there's any change.

Echoing barkingmonkee, you're sure it's overheating and not just an indication problem?

Blown head gasket another possibility. Any other syntoms like water in the oil or coolant smell out the exhaust?

 

barkingmonkeye" the radiator does most of the cooling not the heater core. although the heater core is the same as a small radiator, your car should not overheat even if your heater core is clogged. if your getting decent heat from the vent its not clogged. is your car in fact overheating? have you used a thermometer to test coolant temp after the car has warmed up?"

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A clogged heater core will definetly cause overheating. The coolant circulates through the core regardless if "heat" is selected. With a clog, coolant is not allowed to go back into the radiator for cooling.

 

look high on the cooling system for a bleeder similar to those on brake systems. with the car running but not yet hot open it up a little and when coolant minus bubble flows out close it and you have removed the air form the system.

make sure the electric cooling fan comes on. If it does not you may have found your problem. If it comes on and goes off and comes back on as you idle it is working as it should and maybe you are not over heated.

Ignore the temp gauge. If the system is full of coolant and the top and bottom rad hose are approx same temp. (when hot) the t stat is open, rad flowing and the pump working. If the over flowbottle is not overflowing you may be ok.

when cold, start the car and look into overflow bottle. do you get a bunch of bubbles in a steady stream from the instant the car starts and Does the upper rad hose get hard almost instantly (before it gets hot) ? If yes, you are screwed. A few ranbdom bubbles as it warms up are ok.

pull the dipstick and open the oil filler cap. Do you see anything that looks like coffee w/ cream? if so you are screwed. is the level on the stick rising?

does the car run poorly when hot? Do the lifters get loud? Does it knock more?

Don't worry about the heater core. Feel the inlet and outlet at the fire wall they should be almost the same temp. If you think it will help, connect the two with heater hose and abandon the heater core unit until next winter.

 

I will try some of the things you guys mentioned. There is a tube coming upward out of the water pump with what appears to be a bleeder valve at the top, so I'll try that. I'll also try flushing the heater core with a hose. Yes, I'm sure it's overheating. The coolant definitely isn't flowing properly, because if it was I should be able to get heat. I forgot to mention that the car occasionally lights up low coolant even though it's full. I'm not sure where the sensor is for that, but wherever it is coolant must not bee reaching it.
Well, in the middle of typing this message I decided to run down and check the oil again. It has coolant in it. So my next question is: Anyone want to buy a Lumina? Just kidding. Does anyone know if a cylinder head swap on this car is hard? I've only done one previously and that was a VW Fox.

 

i don't know the details but a bad intake manifold gasket could be your problem. I did one on an '84 gm 2.8 l v-6 many years ago and it was a 1 day job, and once I got the intake manifold off the source of the water into oil leak was apparent.

 

I didn't think of the intake gasket. I was thinking maybe head gasket or warped head. Whatever went out went because of the overheating. The oil was fine a couple weeks ago. I need to figure out a good way to find the leak so I can determine whether I'm even going to bother fixing it. The valvetrain sounded pretty bad last time I started it up.