Rear suspension - PeachParts Mercedes-Benz Forum

betobenz · #1 03-10-2005, 02:00 PM

Hello All.
I have an 87 TDT wagen in very nice shape with 165k on the clock. It appears well cared for before i got it with 142k. I and my mechanic since have looked after it well. My Mechanic has told me the pump on the engine for the rear suspension is not working. He said the bulbs and struts are fine. The car sits level and does not sag in the rear. I have not messed with it because the Haynes manual says its a specialist job. But I just found out where I can get a rebuilt pump for $149.00. My mechanic quoted a lot more than that. This is a job that I would like to try. But first I think I'm supposed to get the rear wheels up on ramps and then go under her rear and move the little valve actuator arm to see if it makes the car rise or lower. I'm also told that that arm could be corroded. While I have pulled and replaced an engine in my 67 Land Rover and did a main seal on my Moto Guzzi Lemans One and other jobs I am fairly ok around the wagon in terms of mechanics-but I am a little afraid here. Please advise if I should even do this. And if so roughly how-The Haynes manual is miserable.

dieseldiehard · #2 03-10-2005, 04:12 PM

no problem on a lift, I suppose if you have a good ramps set up its allright just don't mess with it otherwise because you could get flattened if it comes down on you if you're under the car on the pavement. The mechanic that said the pump is bad should have checked the arm first, it is common to get broken or come off the ball joints. And is the cheapest fix for a problem of this type. Of course they might be trying to sell you a $750 pump (thats the price for the W123 chassis hydro pump)!

tomm9298 · #3 03-10-2005, 04:33 PM

Is there a rebuild kit for the pump? I know the vacuum pump on the diesel has a kit.

dieseldiehard · #4 03-10-2005, 06:21 PM

No, there isn't a rebuild kit only some gaskets to prevent leaking wheere it is driven off the engine. The precision machining of the internal clearances is really very exacting and rebuilding would be a difficult job. Not that somebody somewhere like NASA might attempt it

I had one in my hand and it makes a nice ker-sluck noise as you turn the driveshaft, with a little oil in it of course.
I haven't heard of a suspension pump failing at such an early time but it is possible, especially if the oil ever ran low or ran out !? I hope its the control arm or the valve at the rear end
This might be a job for the dealer, I hate to say that but they have (or should have!) the test gauges and fittings that attach to the pump to readout the high pressure involved. Most Indys would not be that well set up unless they are larger and in a big city perhaps.

lrg · #5 03-10-2005, 11:41 PM

If the rear end is level it's hard to imagine the pump is bad because I believe the normal movement of the car up and down over bumps would force the fluid out of the rear accumulators and the rear would sag. If the car is up on ramps you'll be pretty safe to move the lever, just be absolutely sure the car is secure (wheel blocks, brake on, etc.) An alternative is to try opening the bleed screw in the rear valve while the engine is idling. You should get a slow but steady flow of fluid. If you do the pump is probably working but don't worry if it's not gushing, at idle there isn't a whole lot of pressure. If the system hasn't been flushed for quite a few years or if the rear valve is bad I could see where a mechanic who didn't know the system might think the pump was bad. By the way, it IS possible to rebuild the rear valve.

tomm9298 · #6 03-11-2005, 07:53 AM

Where would you find such a rebuild kit?

odie · #7 03-11-2005, 12:09 PM

my 82 TDT settles when it's parked over night. As soon as I start the engine I can feel the rear suspension rise up about 2 inches.

I don't appear to be losing suspension fluid on the ground anywhere.

Is this "bleed down" normal or are the struts themselves leaking internally?

R Leo · #8 03-11-2005, 12:50 PM

Quote:

Originally Posted by odie

my 82 TDT settles when it's parked over night. As soon as I start the engine I can feel the rear suspension rise up about 2 inches.

I don't appear to be losing suspension fluid on the ground anywhere.

Is this "bleed down" normal or are the struts themselves leaking internally?

Mine does the same thing. No external leaks either. I suspect that it is a small leak in the positioning valve alowing pressures to equalize.

lrg · #9 03-11-2005, 01:30 PM

The bleed down is due to a slow leak inside the actuator valve at the rear end. You won't get a leak on the ground and it has nothing to do with the struts. The valve leaks internally allowing the high pressure side to bleed into the low pressure side so the rear slowly sags, usually overnight. I had the same proplem and bought the rebuild kit to fix it so it works perfectly now. The rebuid is definitely a DIY project. You'll need to completely remove and disassemble the valve. Pay very close attention to how it comes apart as it is relatively easy to put it back together with some parts reversed or backwards (ask me how I know and how good I got at taking it apart and putting it back together). One tip, there is a small piston inside that needs to be fully removed to get at a small seal inside. I didn't spot it at first but I think replacing that seal is critical to getting the unit properly rebuilt.

The rebuild kit is available at the dealer, part# 000-586-00-32, officially called a "washer set" which is why a lot of people have had trouble finding it. It cost $63.68 when I bought it a year ago which doesn't sound too bad until you see how little you actually get in the kit. Even so, to me it was a very worthwhile and satisfying project.

JimmyL · #10 03-11-2005, 08:11 PM

Great info LRG. Thanks!
JL

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