Overheating Issue

[74-AMX]

Hello,
I am new to BMW and recently picked up an '89 525i from an auction. The motor seems to run very well, but it overheats when idling, driving or any time in between. I poped off the thermostat housing only to find there was no thermostat. I let the vehicle run and I noticed that there was no water circulation so I figured that the water pump had failed. I replaced the water pump, installed a new thermostat and I now get a minimal amount of circulation, but the vehcile is still very quick to overheat. I then replaced the fan clutch and purchased a new fan blade as well. The cluth seems to move a good volume of air but the vehicle still overheats. I have check to see if there is any fluid transfer (oil in water or water in oil) but all fluids are clean and clear with no transfer. The compression reads between 145-165psi through the cylinders so I don't suspect there is a head issue and I do not get any bubbling in the radiatior. Can anyone tell me if there is a know or common blockage issue associated with these motors? Is there a valve that I don't know about? Can the auxiliry water pump or heater water valve disrupt the engines ability to cool itself properly? I noticed that when the vehicle starts overheating the upper radiator hose is hot, but the bottom is only luke warm. Water flows through the radiatior very easily if I flush it out. Again, I am not sure how the cooling system is supposed to work in one of these vehicles, I just did the tests that I would do on my AMC Javelins. Any help would be greatly appreciated. Thanks

[dacoyote]

Pisser Line?? Make sure you don't got an air bubble...

Does the heater work?

[JD525IA]

To check it, start the car and pop the hood. Make sure the engine is warmed up to your overheating temp.

Look at the fan as you are shutting the engine off. If the fan continues to go around for a couple seconds after you shut down, then the viscous clutch is bad and needs to be replaced.

What is probably happening is that when you come to a stop, the radiator is no longer getting sufficiently cooled by the air that comes from the car moving forward. If it hits a certain temp, the clutch is supposed to solidify, or lockup, and make the fan turn more via the engine rotation. Did I say that right?

Basically, everytime you stop at a light, the temp gauge will go up, and when you resume forward motion the needle will drop to normal again. Classic symptoms of a bad fan clutch.

Luckily, it's cheap and easy. Good luck.


Oh crap! I just re-read your original post and you already replaced the clutch. Sorry, mate!

[E34-520iSE]

Make sure there's no air lock in the heater matrix - it's really common on the e34.

HTH,

Shaun

[Blitzkrieg Bob]

sounds like you did everything, but bleed the air out.

[74-AMX]

Thank you to all how responded to my questions. I have bled the system multiple times but I have had no success getting the vehicle to run without overheating. Is there a seperate step for evacuating the air from the heater matrix or is that done in the regular bleeding process? Dacoyote mentioned that it could possibly a "pisser line"? Not sure what that is. Any info would help greatly. Thank you all for your time.

[Blitzkrieg Bob]

while bleeding.

Check this site out for more information.

http://www.bmwe34.net/e34main/maintenance/engine/Coolant%20replacement.htm

[632 Regal]

do a search on "bleeding" theres a million threads on the subject. I can almost guarantee thats the problem, welcome to BMW, the V8 engines dont need to be bled :D

[74-AMX]

Thanks again for all the info. I followed the directions from the site on bleeding but before I did so I removed the therostat housing to make sure the arrow was pointing in the 12 o'clock position and it was at about the 5 o'clock position. I have reset the thermostat to the proper position and I am just waiting for the sealant to dry a bit. I have went back throgh the bleeding procedure. I am not confident that repositioning the thermostat is going to be the fix as there was no thermostat in the vehicle when I purchased it and it still had these overheating problems. I will repost wether or not this fixed the issue. Thanks.

[632 Regal]

some threads say to bleed it with the front on ramps, some say to pour coolant through the upper hose etc. Bleeding can be a complete bitch to do properly sometimes and thats probably the issue that has caused the car to go to auction. Also, since it has been overheated probably many times the head and gasket could be fubared.

[74-AMX]

Can you give me any indicators to lookk for regarding the condition of the head and gasket besides the obvious signs of a defective head or gasket (ie. low compression in one or more cylinders, oil and/or water passing through head or into radiator or oil, excessive pressure or bubbling in the radiator or foamy oil?). Thanks for your help.