viscous coupling replacement

[Nik_Codling]

Hi All,

I posted a while back about whether my fan ('89 300CE) should be audibly "roaring" all the time, and it was suggested I check whether the viscous coupling was performing correctly.

Well I checked it over the weekend, using a chunk of dense insultation foam (as opposed to the suggested carrot!), held up to the edge of the fan, with the engine just idling. The fan didn't even vaguely stop turning, and happlily gouged a chunk out of the foam. This would seem to suggest to me that the viscous coupling is either not working (and needs replacement), or has been re-assembled incorrectly, such that it has been prevented from operating correctly.

In the absense of not knowing any different, can any one advise me whether it's possible for the viscous coupling to be assembled in a manner than would prevent it from operating - in other words, can it be inadvertently "locked"? I don't want to buy a new one and find that the one on there is ok, and has just been incorrectly re-fitted.

Second, can anyone advise how I go about stopping the fan rotating while I undo all the necessary fasterners? The fan can still be turned by hand with the engine switched off, although there is considerable drag from the viscous coupling.

Many thanks for any advice.

Nik

 

[grober]

viscous fan removal

Hi Nik,
I think for your vintage of 124 MERC used a small L-shaped rod to lock a hole in the water pump pulley flange from the rear, something like a 5mm allen key. this locks the pulley against a small flange on the body on the water pump housing. This is one to be done more by "feel " than by sight. Later models used a special Y shaped tool which fits over the round allen socket bolts securing the vbelt pulley to the water pump hub. You could try to fabricate one. ?? If you are thinking of replacement have a look at the OEM sachs site "english version" at http://webcat.sachs.de to get the correct version. They also mention that the viscous coupling should always be stored VERTICALLY, to avoid fluid loss I guess

 

[Matt Crooke]

Nick

A very crude way of doing things, but a quick fix for a viscous coupling is (i had this on a Granada several years ago) to simply lock the fan and the coupling together, generally using a screw or nail.

Yeah it stops the overheating problem, but the noise levels and fuel consumption go through the roof!

Have a check to make sure someone hasnt tried this in the past!