We drove my 2005 S600 for about 5 days with the red "ABC Warning - Do Not Drive" message lit, ~15 miles a day, back and forth to work. The car was definitely lower, but wasn't rubbing the tires when driving, and there wasn't any groaning or grinding like a faulty pump. Finally Friday I checked the reservoir, and of course it was empty. Topped it off with Pentosin, started the engine, hit the Raise button twice, then got out of the car to look for drips. Well it wasn't a drip: all that fluid was dumped out under the right front corner of the car. Not under the right wheel, but inboard and forward of that, about under where the right side horn is.
So I put the car up on QuickJacks and could see that it was all wet in what looked like a mess of hoses right under the crank pulley. So I pulled the radiator fan to get a better view, filled the reservoir about halfway, quickly started the engine and ran around to where I could see about where the leak was. It's the line I've seen referred to here as the Pulsation Damper, and it's ruptured in some way, but I haven't got it out yet to see clearly where it broke. (The leak is dead-center of the car, but was squirting to the right.)
Which leads to my question: even though the pump has proved twice that it will pump plenty of volume, will it pump enough pressure when I get the hose repaired? I plan to cut the hard pipe either side of the bad rubber section and have a hydraulics shop make up a replacement rubber section with compression fittings. If I knew for sure the pump was toast I'd skip that step and just do the "recirc mod" to keep the dual PS/ABC pump in place (props to whoever posted that, I forget who it was), then put Yellow Speed coilovers under the car (I know, blasphemy, and I love ABC, but if this hose has gone, then it's only a matter of time before the next one, then a strut, then the accumulators if they're not gone already, etc.). Or if the pump is going to cause me trouble in future even in recirculation mode, then while I have the front of the car apart I could put a PS-only pump in there.

So, is there any hard data to back up the "your pump is toast if you ever let it suck air" horror stories one reads? Because obviously it hasn't seized up, I just don't how it's built and what kind of seals it may use internally that running dry/hot might've damaged. I'll probably just repair the hose and see if it works, then we'll know for sure.

And a related question: I've always read that you have to pressurize the ABC reservoir to get the pump to prime, but mine's primed itself twice from absolutely empty without being pressurized. But that's with a ruptured discharge hose; when it's able to build pressure is it not going to want to prime?
Thanks,
Mike

 

 

Thanks for the encouragement, I think you're probably right.

For anyone who may have a similar situation, I took some pictures. This one is looking straight down between the radiator and the front of the engine, with the cooling fan removed:


A closer shot. I don't know anything about these kinds of fittings, but it looks to me like the "nipple" sticking out the end is just the main pipe/tube, while the bigger section gets swaged down over the rubber hose, thus compressing the hose between the sleeve and the pipe.
And here's the business end of the rubber hose that fit inside that fitting. The rubber sleeving off to the left looks to me like a heavy-gauge rubbery heat shrink tubing, if you've ever used that. It covered the whole hose from end to end, overlapping onto the fittings/sleeves on both ends, like the next photo shows.


That shrink wrap was the only thing holding the compromised connection together. That and the rubber hose basically being pinched between the u-shaped tubing seen above, and a clamp that held this end of the tube on its right side. (The car's left side, over close to the PS/ABC pump, but down low.) The shrink wrap also made it hard to diagnose where the leak was, because just looking at it you don't see anything wrong, and everything down there was soaked with hydraulic fluid. But as I was monkeying with those clamps it became obvious that the rubber hose wasn't connected to the metal piece anymore. And I was able to squeeze hydraulic fluid out of the outer wrap, and it seeped out around the end where it overlapped the metal fitting. So if you ever have a leak and can't see a hole, check for that sort of situation.
And the MB part number is stamped there, which me, my wife, and my daughter read as A220 320 5972 01, but I can't get that to come up with anything. The "0" in "01" isn't well formed, but I've tried "3" and "8" there, and can't get a match on a Mercedes part. Not that I wanted to buy one, just see how much they were, if they could be bought.
And while I'm talking about this thing, mad props to those who got the whole hose out and back in. I looked at where it attaches to the pump and that looks like a b***h to get to, and then there's this crazy sort of metal guard just after the pump that keeps the hose from rubbing on a pulley, so I give much respect to those who have snaked it out of there. (A lot of what I learned about this thing was from Wellwynnick's posts. Thanks, Nick.)

Here's a pic just to show that the hose is made by Aeroquip, which I think is good stuff. I don't know if they made the whole assembly, probably not.
Now I just need to find a hydraulics shop around Atlanta to make up that rubber piece with a 10mm compression fitting on one end and capped on the other.
The capped end got me thinking: if this thing's supposed to be a pulsation damper, what if we attached a proper pulsation damper to the end of it? If we attached Pulsation Dampener 2203270215 or Accumulator 2203270115 to the end of this hose, would that help with dampening pulsations at the pump discharge?
Has anyone ever done this, or looked into it? Seems to have some merit, if the purpose of that pipe is truly to dampen pulsations. And it occurs to me that being a dead-end pipe, all the pressure pulses over the years pounding against the plugged end of the pipe may've incrementally hammered the rubber hose out of its fitting. An accumulator on the end of that pipe ought to help dampen those pressure pulses and make that pipe, and the whole system even, last longer. There's a little room beyond where the pipe/hose terminates, over near the left headlight and inside the curve of the bumper, to fit an accumulator.
Any opinions on this? Wild goose chase?
Mike

 

FWIW that hose isn't terribly expensive from MB. Should be under $200. Comes complete with all the little brackets and new o-rings, yes it's more than having a shop make one up for you, but it's also a direct drop in and saves you time.

I had a hose fail under there and the pump started leaking around the seal within a couple miles of driving it back towards home. AC Delco rebuilt pump was only $250. Well worth fixing and keeping the ABC on these cars, if you can work on them yourself and not get dealer raped, it's a great system.

 

I think that BJ Hydraulics, at the base of Kennesaw Mountain, can do that for you. One critical point is that the orientation of the ends must be perfect - the hose does not flex to rotate!

 

Joe: I was about to ask, "Have you seen what it would take to get that hose loose from the pump end?!?", but I guess you have if you replaced the pump. It was enough trouble just getting the dead-end end loose, and I don't want to have to chase it all the way back to the pump just yet. $200 isn't bad though, so if it was easy enough to get to I'd do that, but I don't want to go there just yet. If after putting it back together I find that the pump is bad then while replacing that I'd probably replace the hose with the OEM item. Although I gotta say, after seeing how this line failed, with the rubber hose basically squirting out of its crimped fitting, I'm more inclined to think that a compression fitting is bound to be at least as strong as those crimped fittings. I've worked around a lot of Swagelock fittings holding 2200# and higher, and never seen one just come apart like this hose has.

Wally: Thanks for the tip about BJ Hydraulics. I live on the SW side of Atlanta, so hopefully I can find something closer, but if not I'll definitely call them. And as for the orientation and exactness, with this piece of hose being a dead-end and just having one connection to a hard pipe that shouldn't be an issue. But I'll definitely keep that in mind if (when) I have to change another one that's double-ended.

 

The pump on my car had a banjo bolt, I believe 18mm. Was easiest to access from underneath. There's a straight shot to it from the bottom through a plastic piece that moves when you put the tool through. It's hard to explain but once you see it, it makes sense.

 

"And as for the orientation and exactness, with this piece of hose being a dead-end and just having one connection to a hard pipe that shouldn't be an issue. But I'll definitely keep that in mind if (when) I have to change another one that's double-ended."

There are several ways to make the hoses, and one way is to use a fitting that screws into a fixed fitting on the hose. That is, they swage a simple fixed threaded fitting onto the hose, and attach another fitting onto the metal end of the hose that screws into/onto the fixed fitting. This gives complete freedom to align the end as needed. Thanks to Capt'n Earl for reminding me of that...

 

Yeah, I'd seen that on another thread, will have to look for that access hole next time I'm under there. Although I'm going to fix the hose and refill the system and see if the pump still works, I'm afraid I'm going to be replacing it. In which case I'll be getting real familiar with that banjo bolt.