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Discussion Starter #1
My 1992 525i recently has been overheating. As i was getting close to home, temperature gauge was going up. As i reached my spot, the gauge was in the red and a very small amount of smoke (steam?) was coming from under the hood. I opened the hood, nothing jumped out immediately. Coolant was leaking out from the bottom of the car into two pools it looked. I let it cool, came back later. Coolant reservoir was half empty, i refilled it and nothing leaked out. I then started the car, again nothing leaking. After idling for a while with no temperature increase on the gauge, i put some gas while still parked. The temperature gauge slightly crept up. I then took it on a small lap and the gauge continued to creep up. I parked it after it touched the red. Still no coolant leak. Anyone have any ideas whats wrong? I have access to lifts and tools so i would prefer doing it myself but if its a very involved job im just bringing it in. Love this car, want to keep it running. Thanks
 

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Discussion Starter #3
Thank you for the quick reply, I have a student run garage on my campus so I will be taking it in and will check if that is the problem. I'm pretty inexperienced with car repairs, at most changing my own spark plugs and ignition coils so i'm excited to see what I can do. Thanks again
 

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Its surprisingly easy to change since its right on top. I suggest getting the metal impeller as a replacement. Also change the thermostat housing to a metal one and fan clutch if you havent already

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Being so new to this, a lot of what you just said is going right over my head. I'm looking it up, so bear with me. The metal impeller is just the water pump but a specific type? The other parts i've found though, but do you have any suggested place to buy these replacement parts?
 

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Discussion Starter #8
Turnermotorsport.com, pelican (kindof expensive) rock auto may have them as well


Here is the link for turner for the water pump https://www.turnermotorsport.com/p-...52-m52tu-and-m54-engines-with-metal-impeller/

The thermostat housing is made of the same composite material as the water pump impeller so they fail the same way
all luckily on the top of the engine mostly
Now with a little more research, i have a couple more questions. I'm going to definitely see if my water pump is damaged, but should i also just order a new thermostat? And the fan clutch may need replacing why? I'm just trying to learn a little too. Thanks
 

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Thermostat wont hurt. The reason for the fan clutch is the fluid inside dries out with age and can cause the fan to seize. If it seizes it can cause the fan to spin too fast and shatter which sends pieces of plastic all over, either through the coolant hoses or the radiator

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Transplanted JrzyBoy
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You are indeed fortunate to have access to a lift

and that usually comes with some free advice from students. If I remember correctly, you'll need a rather long open end wrench (to be specific, mine is 20" long and appears to be about 32 mm) to remove the fan blade, and something tells me it turns in the wrong direction, meaning lefty-loosey does not apply. You gotta turn it the other way (which is of course counter-intuitive. If it's not a hose and the impeller which is part of the water pump has indeed disintegrated, you'll need to replace it with a metal impeller. Pelican Parts supplies me, and they may have a video in their tech support library to give you a step by step procedure. Make sure you use the correct Eurospec'd antifreeze...not the green Prestone. I think a lot of places (AutoZone, NAPA, probably even Walmart) sell Zerex G-05 which is approved by BMW or so it says on the label...I just checked. Or whatever BMW approves. When refilling the radiator, make sure to loosen the bleeder valve on top of the radiator...it's the large Philips head plastic or brass screw and you use the big screwdriver. Don't overtighen it either.... I found it better to fill as many hoses as you can when you clamp things together to minimize getting an air bubble (air lock) in the system. And one other tip...if you see that needle creeping up over half when driving and rapidly approaching the 3/4 mark, better just pull over, leave the car till it cools down and suck up the time lag by logging on to this forum to pass the time while learning whatever because overheating a BMW can lead to that catastrophic warpage or failure of the head, and with cars this old, it may me more economical to just put her down like an old cavalry horse. Not a pretty sight to be sure. Good luck fixing it. Get a new thermostat as well. And shoot, if you've got the money, replace the upper and lower hoses, especially if you're not sure of the history or age of them. Hoses are relatively cheap compared to having one fail next month after you just put in two gallons of fresh antifreeze. Ask me how I know.

BTW, the water pump failure is a well know flaw and you may find that the original plastic or composite impeller has already been replaced. In that case, it's just time for a new one.
 

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Humble E34 lover
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Sage advice from EyeDoc1 :thumbup:
 

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Discussion Starter #12
Replaced all the parts, haven't been having any problems with overheating! Thanks alot everyone for the help!
 

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Discussion Starter #13
Im Back

The car has begun overheating again. I had replaced the thermostat and housing, the fan clutch, and water pump. This problem seems to me to be coming from the radiator cap, as when i'm screwing it onto the reservoir it is not threading properly, is skewed, and then when twisted tightly it jumps up a thread, meaning it can never get fully tightened. This seems to be the clear problem, but before i bought any new parts i wanted some kind of consultation. I'm planning on just buying a replacement coolant expansion tank
 
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