excessive engine overheating

ok so I replaced the thermostat flushed the radiator and the resevoir, added new coolant, no leaks, but it still over heats. the fans still dont come on until around 240 or 250. I replaced the ECT sensor, no leaks but I ended up putting about 2 and a half gallons of anti freeze in it. Is it the water pump? maybe its not letting the water flow through fast enough to help cool?


please help:screwy:

Some background to your overheating issue would be helpful.
One idea though, the water pump on these engines is driven by one of the cams. It uses its own tensioner that is separate from the other accessories. People have mentioned in the past that these tend to loose there strength over time and can lead to overheating problems like yours because the belt will start to slip. My car recently started having over heating problems, I didn't really want to mess around, and the fans were working so I flushed the system, replaced the thermostat and replaced the tensioner and belt. The car runs fine know. In reality I think it was the thermostat, but it probably helped to replace the tensioner. The car now runs at 200 as long as I am moving, or it is cold outside.

Tensioner is around $50, belt is less than $10. You can kind of check by pulling on the tensioner with your finger. It it moves really easily it is probably bad. If its not that and not your thermostat and your fans come on, then you might have a head gasket problem.

I just replaced the entire rad (a buddy did it) because of a major leak near the top, but I notice the temp is on average about 40 degrees F cooler.

I am not saying replace your rad but you seem to have replaced everything else. Correct me if I'm wrong but the water pump usually either works or it doesn't as opposed to slowing down.

I don't want to sound Cynical... But I had the same problem with my Aurora at around 200,000Km (126,000 Miles?) And it turned out I had a leaking head gasket. There was no oil in the coolant or coolant in the oil. :banghead: the coolant was pooling up in the valley between the cylinders. I replaced the engine and had the same problem about 20,000 Km later. I would seriously consider a rebuild on the engine opposed to a used engine (Or, you could Flog the car off on some unsuspecting sap).

Previous owner of a 1998 Oldsmobile Aurora Autobahn (4.0L Nightmare)

I would say it is a head gasket. The fans are not supposed to come on until about 240 degrees. They should come on when you turn your ac on regardless of temp. With these engines all it takes is 1 overheat to pop te headgasket due to poor design of bolt holes where the head bolts go in.

You might want to check the catalytic converter. I just replaced mine. The exhaust backpressure will cause the engine to run hotter than normal. If you can hear any rattles coming from underneath the car you it may be the cat. Earlier this year I replaced hoses, but still had a temp problem. It wouldn't overheat, but would run about 230 before the other fan would kick in. I couldn't figure it out until the cat went out completely. Cost me $157 to have cat replaced. Walt

You might want to check the catalytic converter. I just replaced mine. The exhaust backpressure will cause the engine to run hotter than normal. If you can hear any rattles coming from underneath the car you it may be the cat. Earlier this year I replaced hoses, but still had a temp problem. It wouldn't overheat, but would run about 230 before the other fan would kick in. I couldn't figure it out until the cat went out completely. Cost me $157 to have cat replaced. Walt

Hmm , interesting. My freinds car I though ran a little hot. The fan kick in heavily at 240, and run a lil lower than that, goin down to 210 at times. But on average seems to run right at 245 maybe 250 if its really hot. Something to be concerned about ? What happened, is the car Overheated, cause it thew a belt, consequently destroying the tensioner. So I replaced it. I noticed to day, it seemed small bubbles were coming out of the canister, but there were ever so slightly. I put my hand on the canister, it seemed to have pressure on it. Is that normal. I know they had a lil, but maybe a coolant leak check woudl tell me ? Anbd BTW, not a thread hijack either lol:popcorn: