Unscheduled Maintenance

Driving along yesterday in a mild summer deluge I couldn't help but notice that the wipers on my SLK were less "intermittent - slow - fast" as "occasional - weary - stopped". I expected my bank balance, personal safety or chances of getting the mid-afternoon snooze all to be at risk.

Having an eye for broken windscreen wipers my diagnosis was that the linkage was seized. The Internet says a new one is more than £100 so I'll obviously be taking the old one to bits in lieu of having anything better to do.

1. Remove both wipers; under the plastic caps on the tops of the spindles are nuts and then a bit of wriggling to get the wipers themselves off the tapered shafts.
2. Remove the plastic bulkhead shield - half a dozen self tapping torx screws then a bit of pulling. The washer jets are attached to this so just plonked on top of the engine so I didn't need to disconnect them
3. You can now see the wiper mechanism; I removed the nut which connects the linkage onto the motor (after marking it's position with tippex so I knew where to put it back...) and the motor was able to whizz around quite freely on it's own. Also I tried to move the linkage by hand and it was going nowhere - Diagnosis correct!
4. There's three bolts holding the wiper mechanism to the car - one above each wiper spindle and one on the bulkhead. Because the linkage was jammed in an odd position I had to also detach the motor to get it out (three more bolts in the middle of the big metal plate on the linkage.

Once I had the linkage out it became obvious it was seized as balls. I put it in the vice to work it back and forward with a big lever and all the penetrating fluid which freed up a little but it was never going to be right. Also I couldn't tell if one or both of the two spindles was seized. It needs to come to bits.

Can you take the sodding thing apart? Unbelievably, you can. Each of the spindles sits in a housing like this:

I am good drawer.

It's a simple case of pushing off the circlip (which is actually very easy). I did the driver's side one first and the spindle fell out of the housing with only a slight bash with a hammer. That one's ok then. Then I tried the passenger side (centre) one and, well, that was stuck.

After several rounds of violence and bad language I managed to get it out. It dragged one of the bearings out of the housing with it.

My theory about what's gone wrong here - the depression that the o-ring sits in was full of aluminium corrosion. That had forced the o-ring against the spindle and it had worn away (it was more "D" shaped than "O" shaped). Water got in and sat in the void between the two bearings and that filled with steel/aluminium corrosion. My guess is that this isn't so bad until it dries out and since there's now no water to lubricate it, it suddenly seizes.

Here you can see the spindle complete with the (plain, brass?) bearing that got pulled out of the housing. In the middle you can see where I've cleaned up the big glob of corrosion. To the left is the actuating arm and to the right is the groove for the circlip.

Anyway, all the bits were cleaned up, lubricated and re-assembled (including pressing the bearing back in) and... everything worked perfectly - better than ever in fact. I didn't have a replacement o-ring so I reassembled it with the old, tired one, however I can change that with  the linkage still on the car next time I have cause to be ferkling around in there.

Total time taken - about two hours plus procrastination.

Now, stop raining and breaking.