Viscous Fan Clutch

[lip277]

I am chasing a cooling issue on my (mostly) stock 2800CS....
The PO installed a later 9 blade fan and clutch. Works fine for the most part but the temps always ran warmer than I thought they should.

I have replaced the TS
Drained and refilled the antifreeze (with 40% concentration) and used Water Wetter.
Runs very nice (cool) now even in the warmer weather as long as the car is moving.
It used to run warmer so I feel I have addressed most of my problems.

But - (Isn't there always a 'but'?)
I ended up yesterday in some stop and go traffic. When sitting - the temps would creep up 3/4 the way to the red. As soon as I got to speed again - back down to the 'normal' position (with needle just about horizontal)

So I am suspecting the fan clutch.
As noted - There is later clutch and 9 blade fan installed - What is the 'preferred' fitment to choose from to get a replacement? Is there more than one choice?

I have seen 11521260459 used on E12, E24 and some E9's but don't know if there are other choices..... OR if there are different styles that I would have to match to (depending on what I have installed already).

Any thoughts would be appreciated.
Thanks-

 

[bert35csi]

A radiator shroud will probably will alleviate and possibly solve the high temperature problem during idling and low speed operations. The shroud will help to "centralize" the air coming through the radiator instead of the fan pulling air from every which which way. I suspect that the later viscous 9 bladed fan system work best with a shroud in place. The original fan setup on my previous CS did not exhibited these cooling problems.

My coupe uses the same clutch/fan as yours and it exhibits the exact same cooling faults as yours. I too have change the fan clutch, thermostat, coolant, a new radiator and the problem still persists. I've bought a new shroud (still pretty cheap) to install on my coupe but have yet had the opportunity to do so. Hopefully when installed, it will solve the nagging problem.

Bmw shows the shroud in their part catalog, but very rarely have I seen one install on a coupe. This application may be for the very late 74 and 75 coupes.

Radiator - BMW parts catalog

 

[OCCoupe]

When I purchased my Coupe it ran in the mid range unless I was stuck in traffic on a warmer day or I was driving aggressively on hilly road. I replaced the thermostat with a cooler one and flushed the radiator, this really did not help. I took it to my mechanic who felt around the radiator and was able to show me cool spots which he explained were areas that had calcified build up or scale which restricted flow and capacity. He removed the radiator and had it re cored and cleaned, problem solved. The temperature is constant and even in the warmest days we've had with hard driving the temperature stays put.

 

[Honolulu]

Imnsho

The shroud could be used but your problem is elsewhere and there's a good chance the shroud won't solve the problem. I can also tell you that a shroud from a E12 won't directly fit.

Cooling systems that don't, in stop and go traffic, show that the radiator isn't up to snuff. Recoring is one option but I had mine rodded out by "some old guy" to whom I gave $40. He did it on the spot with me standing there in my nice clothes. He was quick and you could see that he'd done this many, many times. No wasted motion, no searching around, no fuss, clean job all the way through. Plus, he found and fixed a pinhole leak in one of the tubes.

Another possibility is that your tstat isn't opening as it should. This is easily testable in pot of boiling water.

Trick from an old timer ex-dealer top tech (obviously not me): drill a 1/8" hole at the 12 o'clock position of the tstat.