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New to the forum and really new to BMWs. Brought back a 1997 528I from Japan a few months ago (in the Navy, stationed there). Anyway took a chance considering it only had 55k miles on it and was DOT standard. The first overheat happened about 2 months ago, a BMW mechanic charged me $400 to replace a hose that busted under the intake manifold. The car ran great for about 800 miles when it overheated again, this time real bad considering I didn't notice it in the red. Needless to say obvious signs of blown head gasket. Ordered the gasket set, took off the head and discovered 4 hairline cracks around the head bolt holes on the head. Replaced with rebuilt head, replaced water pump and thermostat. Suprisingly (because I don't claim to be a mechanic), she started up right away and runs better than before. But...still had an overheating problem. I was told by a radiator shop that I might need a new fan clutch, so I went ahead and replaced that too. Still running hot, so I replaced the radiator because I noticed a broken neck to the upper hose and it looked kinda cruddy, bought a new cap and even a new coolant resevoir. It's still running up to and sometimes in the red. Through the entire process I've been bleeding the system as much as I know how. I'm starting to think it may have something to do with my heating system since I noticed only the passenger side gets warm when you turn the heat on. Could this be my problem? An actuator or something? Something electrical? No leaks anywhere. Trying to stay away from the dealership to keep from getting raped and don't feel like I can trust anyone anymore. I've gone this far and don't want to give up. Sorry for the long story, but I didn't want to leave anything out. Thanks in advance for any suggestions.
You probably have air in the system, and need to fill and bleed it properly.
I believe you have a bleeder screw right by the radiator cap AND one on the thermostat housing.
With the engine off, crack both bleeders so that air and coolant can easily come out the bleeders. Fill the system with coolant slowly, until a solid stream of coolant comes out of the bleeder at the thermostat, and tighten it down. Continue filling until coolant comes out of the other bleeder screw, and tighten it down.
Put the heater controls to max heat, and with the radiator cap still off, start the engine.
Now, get out of the car, and manually rev the engine to about 1500-2000 rpm, and look at open expansion tank, you should see a stream of coolant coming out of the bleed hose into the expansion tank. It'll spit and sputter a bit while the air is coming out. This is good. Verify that the pump is primed and pumping coolant via this indicator stream, and that the coolant level is good.
Install the radiator cap and let the engine run. Get in the car and watch the temp gauge. Hold the idle a bit high, and when the heater has gotten hot, turn it off, and make sure it doesn't overheat.
Performed the bleeding technique. Seemed to be a little better since I got down the road about 10 miles before deciding to exit and head back. While slowing to exit, the guage slowly climbed towards the red, real close to the light coming on. As I started back on the highway, she started cooling down again until I got to my exit (about 10 miles, then she actually went red). Pulled over, let her cool for about 5 minutes and was enough to make it home. Should I do another bleed? When I bled her the first time I never really saw the stream of coolant to verify the pump is primed and pumping coolant. While holding it at about 2000 rpms, coolant was blowing out of the reservoir.
Note: the passenger side vent still blows but doesn't get warm at all...but I'm guessing this is a separate problem and might not contribute to the overheating.
When the coolant was blowing out of the reservoir, while you were checking for flow, was it because of the engine warming up, or do you think that maybe you're getting combustion gasses in the cooling system?
You may have to have it tested for combustibles in the coolant.
What's the weather like where you are at? Are you using the AC? Your auxillary fan may not be working.
Originally posted by TECH@Jan 27 2004, 08:26 PM When the coolant was blowing out of the reservoir, while you were checking for flow, was it because of the engine warming up, or do you think that maybe you're getting combustion gasses in the cooling system?
You may have to have it tested for combustibles in the coolant.
What's the weather like where you are at? Are you using the AC? Your auxillary fan may not be working.
You say you replace the water pump, correct?
The engine was cool when the coolant was flowing out of the reservoir at 2000 rpms. I did replace the water pump and the thermostat, radiator, fan clutch, cap, small overflow hose and reservoir. Coolant is starting to get a little expensive so right now its about 75% water and the rest coolant until this problem gets resolved.
How do I get it tested for combustibles? Drain some into a container and take to radiator shop? And, if I do have combustibles, what could be the cause and is it correctable?
The weather has been hovering btwn 50 and 65 degrees lately, not using A/C.
mine is a 98 528i,
replaced water pump
Thermostat
Thermostat housing (it was cracked),
I still have the same problem....I go about 10 miles, it starts to heat up, then when I accelerate it goes down...
sometimes it just overheats and accelerating doesn't help...I use the housing as a pressure release....some heat comes out in the form of antifreeze and bubles and steam....and I can keep going with normal temperature...until it all happens again...
Bought it from a dealer, drove home 45 miles ok. Next day while driving the 5 miles home from work, the top hose tore. Replaced that ok, but coolant started to overheat after 1 minute of driving. Had it towed to a garage who changed the thermostat and the water pump, but still having pressure building up in the top hose when driving. They now think it's a head gasket issue, which is gonna cost a fortune.
As you are saying that only one side of the car heats up with the heater on the problem may have something to do with a heater matrix - The heating system of a car is in fact a part of the cooling system for the engine. You have 1 or 2 small radiators hidden usually behind the dash or center console which are used to heat the car (by blowing a fan through them). These radiators (or matrix) are connected directly to the flow of your engine coolant system (where they pick up the hot water). Now, if one of these were to become blocked it would restrict the flow of coolant around the engine, causing overheating and obviously the heater wouldn't work properly. I would suggest flushing the coolant system thoroughly with a rad flush solution and possibly inserting a hosepipe into a hose and blasting the system through (not hard enough to damage the matrix though). Otherwise get a mechanic to check the matrix and the rest of the heating system for blockages.
Just a tip for anyone who suffers overheating while on the road from a radiator fan failure, a solution to get you home - turn up the heating to hottest and put the fan on full this will keep the engine cool by blowing through the heater matrix and cooling the fluid (but not you of course) I have driven over a hundred miles on a hot sunny day using this methed to get me home.
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