My car will run around 206 to 217 and then drop back down and then go back up...after driving for a while it'll run from 212 to 222 then go back up and down....then it'll run from around 217 or 222 to 234....the hottest today and then go back down....when i turn the ac on it goes down...then it'll start going back up...when i turn it offf it'll go down then back up and so on...turn ac on go down then go back up and turn off go down and then back up....not losing any water....can someone help out.
Most modern cooling systems are pressurized, the operating pressure is determined by the radiator cap. Check the pressure rating on your cap, and you can determine the boiling point of water. A 14 psi cap = 245 degrees F, at 16 psi = 250 degrees, etc. Coolant ("antifreeze") runs higher than that. Modern engines are more efficient at these higher temperatures, which is why they use a pressurized system. So if you're not getting any caution lights, and you cooling fan(s) are working, you're probably OK.
But this also explains why you NEVER remove the radiator cap while the engine is at operating temperature - the reduction in pressure in the entire system means ALL the coolant is above its boiling point, and it WILL all try to get out at once!
SOURCE: Hello, My 1992 Cadillac Seville
Help is HERE!
It looks like an Air lock scenario!
Park vehicle on level ground, when cold remove coolant filler cap, start engine and leave to idle, turn heater to hot blower on full. When at operating temp keep clear of coolant filler area and listen, hopefully gurgling then a boil over, wait and then top up with very warm water/coolant let settle it may boil over again whilst air is still in system.
Check for heat inside car, if hot and coolant settled replace cap but keep an eye on temp gauge for a while as air lock may still be further along cooling system.
Please press the Blue button if sorted!
Paul 'W' U.K.
SOURCE: We have a 1996 Cadillac Broughm, and today while
Check that the arm that goes between the rear axle and the level control on the body has not come off or broken. You can pull the fuse temporarily to keep the pump from running so the battery does not go dead.
SOURCE: 1999 Cadillac Seville STS Overheating
Sounds more like an ignition control or coolant flow problem. Or, a/c fan not coming on with a/c.
Getting the water pump question out of the way, the pump either works or not. If it leaks it will cause an overheat due to coolant loss on flat ground or grades...doesn't matter. If the pump bearing or seal is bad it will still pump, it will just be loose and noisy. Coolant flow through the radiator is also essential...I don't think you have a problem there because generally this happens with less maintained higher mile cars.
A bad map sensor can cause your problem because it changes both ignition timing and fuel mixture, either of which can cause very high temps in combustion chambers especially when under a load. Mass air flow sensor can also do this but usually will cause idle problems. If fan is not on with a/c if the remainder of your cooling system may be enough to maintain decent temp control but cannot do this under a load. A/C turned off removes some load and therefore allow you to get up hills. Operating marginally, you can be pushing some coolant out of the system at times without even knowing it.
Now, about your engine: These engines are in my opinion a very poor design to begin with. Even with the best maintenance and low miles, they don't handle temperatures well. at this point, I'd be concerned that after repeated overheats and near overheats, your head gaskets may have started to fail, even though they were not the cause of the problem.Keep that in mind.
Have the items I mentioned tested. If you finally have the problem solved I suggest you change the thermostat as well...Overheating makes them unreliable.
SOURCE: Hi, my 1998 Cadillac DeVille is overheating for no
The most common overheating problem with the Northstar engine is a blocked purge line(small hose).The purge line is designed to purge air out of the cooling system.
There is a small diameter hose coming from near the top of the coolant tank (not the cap) ,this is the purge line.
With the engine idling,pull the purge line from the tank,if there is no coolant flow from this small hose,it is blocked and this will cause overheating.
If the hose is clear, check for blockage at the nipple on the tank.Or trace the hose back until you find the blockage.
The hose goes in to the engine to a crossover and comes out the other side close to the thermostat housing,the blockage may be there.
Print this off if you can and show it to your mechanics......this simple blockage is very often overlooked even by the most experienced mechanics.
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