Viscous clutch/fan repair

[LeaUK]

Here's some info specific to repairing the SL clutch that I wanted to share. An explanation of operation can be found in the Tech Help forum so for this, it’s best to search there first.

My car is a '93 500SL and has the classic symptoms of no fluid remaining within the clutch. ie you can easily spin the fan blades by hand.

Here’s what I’ve completed so far:

1. Removed all plastic cowling – 2 minutes

2. Removed fan blade assy.

3. Removed clutch – there’s a hex cap head bolt (M8/M10) through the centre (standard thread) this needs a long lever and plenty of force

4. Removed the bi-metallic strip and pin – push the strip down at one end (inspection reveals which end) and slide. Remove pin with fingers.

5. Refill clutch (30ml – not sure how much to use as all clutches are potentially different) with Dow Corning 12,500CST silicone fluid by using a 5ml syringe. Force the fluid down the hole that the pin originally sat within.

6. Reassemble

The clutch feels much tighter now and next week my plan is to measure the RPM at:

idle
<95degC @3000RPM
>95degC @3000RPM.

I’ll let you know the results soon...

Here are some pics for info too: