M60b40 Overheating in traffic

Most likely the viscous clutch/coupling of the large fan just in front of the engine has packed in.
BMW P/N: 11527502804
It is quite expensive if bought through BMW but can also be had by 3rd parties for a lot less.

Cheers
Reinhard

Check your expansioncap, is there 200 or 240 ???

Check also the electric pusher fan, which will normally run in low-speed on hot days in traffic. You may have a failed, low-speed resistor on it. If it runs when the A/C is on, it's OK. Some electric fans, however, become completely stuck, as the internal parts eventually corrode and the magnets come off and jam.

The radiators also tend to fur-up over the years and it's also possible that the rotor on your water-pump is failing.

It is said that the early translucent expansion tanks have a greater tendency to burst and should be replaced with the later all-black tanks. At some point on late cars, the pressure relief valve rating in the cap was also reduced to 2.0 bar and there was a recall for earlier cars.

Also the visco coupling can be "refurbished" ( at least while looking for a new one ) using some Silicone Oil. For example we have rebuilt some of them at our club using the Toyota SILICON OIL with the following reference number : 08816-03001 ( aprox 6€ )...

Zitat von VasJ;102656

The big fan in the front of the engine seems to be spinning fine .

The clutch works similar to a thermostat. When the engine is getting hotter a valve opens and oil makes its way between the two parts of the clutch providing friction. The hotter, the more friction, which makes the fan spin quicker powered by the engine. Once the oil has leaked (happens) it will only spin like a windmill but does not provide any cooling anymore.

Zitat

Does it mean its the resistor causing the problem ?

Yes, causing A problem. To my knowledge the resistor is only reqd for the standard first stage whereas the second stage (full power) which kicks in as soon as the water temperature (or a/c pressure) has passed a threshold does not rely on the resistor. Resistor needs replacement nevertheless.

Also: check your water level @ cold engine - common theme upon replacing parts in cooling system: air bubbles.

dudu
Pls elaborate on procedure and success of fix.

Cheers
Reinhard

Zitat von reinhard;102660

dudu
Pls elaborate on procedure and success of fix.

Hi. This URL will point to a traslated version of the spanish version ... Hope it will be clear enough. Anyway, if somebody has some doubts, i will try to explain.

http://translate.google.com/tr…ion-del-viscoso-373263%2F

Another one with more photos..

http://translate.google.com/tr…cion-de-viscoso-147728%2F

And latest one, plenty of photos and details...

http://www.bmwfaq.com/f16/bric…-525tds-e34-fotos-351795/

Cheers,

Thanks Dudu, this looks like an easy enough fix and seems to be what is needed. I am surprised to read that it requires several mL of that stuff, I´d have expected it to be only "very little".

Now... what about that rechroming method?

Reinhard

Zitat von VasJ;102618

I got this strange problem , while driving on A406 my car suddenly started to overheat and blew the expansion tank. So on the following day i swaped the expansion tank with a brand new one , drained the coolant and filled it with a new one . Now its all fine except sometimes its overheating while staying in heavy traffic (ussualy on the sunny days , above 26c) . When i switch the heater ON the temperature goes back to normal . Any ideas what can cause this ?

I would also suspect air in the water system. They are notoriously difficult to bleed successfully. I had a similar symptom after replacing the radiator. It took several bleed attempts over the course of a run (with top up water on board for when she had cooled down).

Zitat von VasJ;102656

Are you talking about the small fan behind the bumper ? Just checked it and its not spinning at all , no matter if the AC is on or off . Tried to put 12v directly into the connector and voila , it started spinning . Does it mean its the resistor causing the problem ?

The connector has three wires: (1) a ground and (2) a high-speed and (3) a low-speed connection. With 12v applied directly, to the connector, you should be able to get the fan to work both in low-speed and high-speed. If Low-speed does not work, then you have a failed resistor. I beleive that BMW have a "resistor kit" available for replacement. If your fan works both on low-speed and high-speed when you apply power directly, but does not work normally, then the next items to check are the fuses for the fan circuit and the two relays in the engine-compartment fuse-box.

[QUOTE=VasJ;102656].


Says 200

=OK