Date registered: Jul 2007
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ACS Pump failure
My story which may be of help.
I had a 160 ACS that the pump failed on. The symptoms started with the car suddenly reporting an error on the dash an the car refusing to go into gear. At first if I switched the car off for five mins and on again it usually fixed itself. However the fault quickly got worse to the point it wasn't driveable.
I found that a sharp bang to the passanger side wing got the car going again for a short period and when I discovered this was where the ACS pump was I decided to investigate.
I would recomend having a go at this yourself if your handy with the spanners as its not that difficult and you'll save the £600 odd pounds the stealer wanted to charge me to fix it. Even if your pumps totally buggered you can very easily fit it yourself saving £90 an hour at the stealers.
Remove the passenger side wing, very easy as its just bolted on. behind it you'll find the pump it looks like a large cylinder with a tube coming out the end and a smaller cylinder on the side. I removed it completely as at the time I didn't know what was wrong with it but I suspect you can just unbolt it so you can get access to the electric motor on the side ( the smaller cylinder).
If memory serves there where two screws holding the motor casing on, undo these and pull the casing off to reveal the rotor and actuator. Look closely at the rotor end which is towards the tube end of the larger cylinder, you should see a sort of structure holding two blocks of copper either side of the rotor. Theses are the bushes and in my case these where the problem as they had worn out (after 60K miles!! come on mercedes).
these blocks have a silver wire coming out of them through a cut out in the cage. As the bushes wear the wire moves along this cut out until it meets the edge of the cage and can no longer self adjust at which point the pump fails.
to remove the bushes carefully prise open the end of there runners, slide them out and cut the silver wire (remembering to leave enough to solder you new bushes to). Surprise, surprise Mercedes doesn't stock these bushes (not in the UK anyway) so it was off to my local autoelectricians who where able to source me a similar set for the princely sum of £10. fit in reverse order to removal, being careful with the motor casing, it contains magnets around the inside so it can be tricky to get the rotor end into the casings bearing. and remember you'll need a soldering iron to re attach the bushes silver wire.
If like me, you remove the pump completely and let all the hydrolic fluid out, a simple way of bleeding the system once the pump was re attached is a s follows.
switch the ignition on with the bleed valve open, close the valve ans switch ignition off, repeat a few times.
so to sum up a couple of hours work and £10 or £600 to the stealer.
Hope this helps.