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Caretaker '11 GLK RWD, '04 C240 4matic- totaled, '92 500SL-sold, 95 320E-sold, 85 300TD-sold
1,692 Posts
Discussion Starter · #1 ·
Buddy across the street is a Ford millwright, decided to give me a hand, turns out it was just a loose hose in the pump assembly, took 20 minutes to figure it all out and reinstall, works like a charm!

If you want to try the following, DO SO AT YOUR OWN RISK

You'll need two small precision flathead screwdrivers as well as the MB tool kit

What I did:
1. Carefully lifted out pump, had to cut tie wrap that held on the vacuum line to get slack- DON'T CUT THE LINES

2. Marked all the vacuum lines AND drew a diagaram, just in case- dont mix up the lines

3. Connector was a bitch until we figured out it had a slide clip- use a small screwdriver to CAREFULLY slide the clip to one side until the connector comes loose

4. Use tool box pliers to gently lift off vacuum lines, grab them by the "T" otherwise they or the connector may crimp and you'll be SOL

5. Draw a quick sketch showing the round thing and the position of the two connector heads.

6. There is another slide clip on the side of each connector head, carefully pry out with small screwdriver- don't mix these heads up as I believe they are plumbed differently

7. Remove the two Phillips screws, turn the unit upside down

8. You'll see six or so small tabs that seem to bond the bottom to the sides, carefully break these off with a very small screwdriver- they dont really seem to serve any purpose other than assembly guides

9. You will now be exposing the circuit board- BE VERY CAREFUL!!! Gently use the 2 small screwdrivers to separate the bottom of the pump assembly from the case, you need to twist and lift but it is easy, need to get clearance between the sides and the tabs on the bottom. Make sure the pump stays upside down until reassembled.

10. Keep the little black pieces of foam, they separate the circuit board from the bottom. As soon as I lifted the board about 3/4" I could see that one of the silicone tubes had come loose from its barb. Reconnected it, put the circuit board back, put on the black foam pieces, snapped the bottom to the sides and badda-bing, badda-boom, done.

"NEW OWNER" of a 1991 SL 500 weekend toy. Hope I don't go broke maintaining it!
600 Posts
I just tried this procedure. I only wish I had a loose vacuum line. That would have been easy.

To help others following this - they should know you do NOT have to remove each individual YELLOW vacuum line from the harness, there are 2 harnesses and they each detach with their respective lines remaining connected (except note the side clip - I broke my clips not noting this).

Mine is now worse than it was prior. At least before I'd get IR read out of red/green at each door/trunk. Now only the passenger door will respond with Red/Green to the IR even though I have a brand new FOB key bought at MB.

Now I have to lock everything manually as it no longer recognizes the IR signal. (YES, I did resynch several times and no, still not working)

Why. Why. Why don't I let bad enough remain bad instead of making it terrible.

Greek God of the R129
8,565 Posts
I had the same problem, driver side didn't work.
After opening the door and removing the latch, inside there is a small pin that broke.
(Very hard to see.)

I am not going to replace the latch $$$
So I rigged it up to work with the key.

If I find a good used one fine. ;)

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