My 2004 BMW 525I has developed a problem with oil getting into coolant system. Dealer says cant fix what they consider to be a leaking head gasket or cracked head. They want to replace engine because they are unable remove head bolts without stripping out the threads in block which they can't repair if they do. I talked to engine block sealer companies and they say their block sealer won't work if the oil is getting into the water. Any suggestions? Other than buying an engine. Car has just over 150k miles on it. BoB Wall email address is [email protected]
I am say this on the assumption that you have an automatic transmissionI. If so the oil in the coolant system will be automatic transmission oil from a cracked oil cooler in the radiator . A simple radiator replacement will fix the leak and a radiator /block flush will take care of the residue . Next thing if the car is running well then there will be nothing wrong with the head gasket or a cracked head as if these were evident the engine would be running like garbage. Next point if the head studs were un- removable because of stripping of the threads in the block then there is a product call HELICOILS that are screwed into the stripped holes and renew the threads back to new condition. So you want suggestions I suggest that these so called mechanics saw you coming and expect to make big bucks out of you. Find another accredited BMW service dealer or a qualified engine re-conditioning engineering shop. I suspect that you are being set up to be ripped off as a motor from the wreckers would cost less that what has been proposed for you.
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: 1995 BMW 525I over heating issue. I repaired head
Hi, Sounds like you have tried about everything. Ok the aux. coolant switch is for the electric pump for the heater core will not cause an over heating condition just a longer warm up of the heater core. Has the cooling system been bleed properly if there is a trapped air pocket it will not let coolant circulate. Was the new thermostat installed correctly? They have a vent that needs to be towards the top or they trap air on the back side and cant take an accurate reading to open and close. Other areas to look at would be proper operation of the fan clutch, if they fail they can cause the fan to not lock up properly and supply enough air movement through the radiator. The aux. electric fans and their temp switches do you hear them coming on are they coming on at the right temp.
SOURCE: My 2002 Sebring 2.7 L
Not knowing what the dealer did to diagnose your problem, the first thing that comes to mind is a clogged/defective thermostat. When coolant backs up into the reservoir, it's an indication of a blockage and that blockage is typically the thermostat. The problem shouldn't be related to the AC system at all.
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