drewk88

Nick,

I don't think raising the engine would make removing the banjo bolt easier. I put the 3/8" ratchet in from the front of the pump with the pump pulley already removed. It took lots of torque to break loose the banjo bolt. There isn't room for a longer ratchet handle because the close distance to the radiator. I do think it's important to remove the shroud completely. To do that, you need to disconnect the transmission cooler line where it connects to the right side of the radiator about 2/3 of the way up, not much fluid will leak out it you keep the end high. Also remove the two plastic clamps holding the top of the radiator. Disconnect the fan wire plug and lift the shroud/fan out gingerly being careful not to break plastic tabs. If you maneuver it just right, not much force is needed. If you use force, something will break. Then re-connect the fluid line until you re-install the shroud. I could not break loose the bolt with the ratchet alone, the bolt was too tight. So I clamped vise grips to the end of the ratchet handle, at 90 degrees upward. Then after getting the socket on the bolt head, I put leftward pressure on the ratchet handle with my right hand and pulled the vise grips leftward with my left hand. I had the front of the car raised so it was at comfortable working height.

kraut56

Fantastic stuff - it gives me hope that I can do anything on this car!
(mine is an April 2002 manufacture, but everything looks good so far).

Does anybody know how to find the "Rodeo" exercise in DAS or Xentry?
I haven't spent much time in DAS yet.

Merry Xmas and Happy New Year to everyone!

shardul

iTrader: (1)

Control Units>Chassis>Suspension

Welwynnick

Thanks for the advice Drew, really appreciate it. Would you recommend removing the poly-V belt as well?

The ABC reservoir was empty, so of course I'm worried that I've damaged the ABC pump as well

EDIT:

After removing the fan and serpentine belt, the pump does turn smoothly and firmly.
It spins round easily enough, but stops immediately.
It was replaced by a previous owner, and it definitely feels new rather than knackered.

I've been looking around for a new damper pipe, and I'm wondering what's really required of it.
After dipping into hydraulics a bit (a new field for me),this is a quick summary of what I found:
It seems that ABC is mostly a conservative, conventional system.
200 - 300 bar is normal working pressure for industrial hydraulics.
They're proof tested to 2x that, and expected to fail at 4x.
Small bore pipes commonly have two layers of steel braid, and cost a few pounds per metre.
End fittings cost a few pounds, and the swaging ferrules are pennies.
Swaging machines (which can press tens of tons) are expensive, but there are lots of companies that service and repair hydraulics.
New pipes take a few minutes to make, and generally cost a few tens of pounds - about a tenth of what Mercedes charge.
Industrial pumps, pipes, valves and telescopic rams are relatively cheap and easy to repair.
My impression is that they're INTENDED to be serviced and repaired periodically.

ABC hydraulics, by contrast, are tightly packaged into hot, vibrating, corrosive environments, but are "intended" to be fitted for life.
It shouldn't have been difficult to see that it wouldn't work out like that.
I think Mercedes should have designed the system to have been more maintainable.
However, looking at the V12TT engine bay, its hard to see how they could have done anything else.
At least they didn't make Lexus' mistake and mount the suspension pump directly above the alternator.....

I'm struggling to understand the requirment for the damper pipe. It looks like an afterthought of the development process. If its just there to damp pressure pulses, then I could presumably get someone to make a terminated 2 ft hose, and route it somewhere convenient. Alternatively, maybe I could connect a reservoir sphere to the end of a short pipe. On the W216/W221 ABC pumps, it looks like Mercedes HAVE added a sphere to the pump itself - they probably wish they'd done that all along with the earlier cars, but that's the price you pay for being a technology pioneer....

Nick

drewk88

Yes, you should remove the serpentine belt, but first break loose the three fasteners on the ABC pump pulley. Then after removing the belt, remove the pulley. Spin the pump by hand, it should not be hard to turn, but a new pump will feel tighter than a worn pump, which will turn very freely.

Well, I would change the hose first, put some fluid in the reservoir, then pressurize it to 1 bar or so if you have the means, start the engine and see if you get pressure to raise and lower the car a few times while monitoring the fluid level in the reservoir. Fingers crossed!

Welwynnick

Drew, you're right on the money. Removing the fan and poly-V belt isn't difficult (you do have to take care) but I think its quite essential to gettting adequate access down there.

The socket wrench was good advice, too. My trusty 1/2" wrench wouldn't even go in there. I have a decades-old 3/8 socket set, but the wrench has something like 40/48 teeth, and that's too coarse to rachet in the space available. I went out and bought an expensive 72-tooth wrench. Its a pleasure to use and does the job perfectly. For anyone who wants to remove these pipes or the pump, I'd say plan a little further ahead than I did and buy a 72-tooth wrench online for a modest amount, and don't even think about proceding until you've done so. Its a no brainer.

I got the burst vibration damper pipe out and went looking for spares or repairs. I didn't hold out much hope of avoiding spending hundreds at the dealer, until I found a hydraulics/pneumatics workshop a few miles from home. On the phone, they said don't repair hydraulic pipes, as used flexible hoses cannot be reterminated, which is something to bear in mind. A new one sounded fine to me, so I went down there and had a good time looking at the guy's face as he tried to work out what he was looking at. It was a picture, until I explained what it did.

The bent-pipe fittings are Mercedes proprietary, so he couldn't make anything EXACTLY the same, but he did suggest cutting the end of the metal pipe, putting a compression fitting on the end, and adding a terminated flexible hose to replace the failed section. The termination would be removable, so as to bleed the pipe. Nice. He did that while I waited, and it only took a few minutes. This all proved the worth of getting the part into the hands of someone who knows what they're doing, and has done it every day for a long time.

I pushed my luck and picked his brains about hydraulics in general, and what Mercedes had done in this instance, and he was happy to chat for a while. It seems that there's nothing special about the hardware, the pipes are what they call two-wire (twin layers of steel braid within the rubber hoses) which is typical for run-of-the-mill hydraulics. These pipes and fittings typically run at 300 bar, with ABC at the low end of commercial hydraulic systems pressures. He gave me some O-rings to replace the slightly squashed ones that came out of the banjo fittings, but was quite confident that I could use cheap nitrile O-rings from a large box-set that he dipped into for all his other customers. Do a search for "419 piece O-ring set", and you find what he used.

There was nothing challenging about doing this repair, and even finding this workshop was easy. For anyone in the UK, the chain is called Hopespare, and I thoroughly recommend them. There are lots of workshops around, and it was all very painless compared to going to a dealer. Best of all, he only charged me £39, and this is what I got:



Nick

drewk88

Nice Job Nick!

I think you just saved me at least a few hundred dollars.
I was preparing to get a new one from the dealer. Mine has a split in the outer jacket of the rubber hose, near the end. I think I should replace it before it leaves me on the side of the road. I'll find a local hydraulic shop as soon as I return home.

I suppose the repairman could have replaced the other hose section as well, using the same method and couplings?

Well, did you get the car completely operational, ABC working and everything?

I think the pulsation damping system design consideration is twofold.
Proximity to the pressure source to reduce fundamental noise and vibrations.
Tuning to reduce harmonic and resonance effects of system geometries and elasticities.

Too much information at this link:
http://turbolab.tamu.edu/proc/pumpproc/P10/P1025-39.pdf

Welwynnick

Yes, I presume the same repair could be used on the other hose. I think there are many ways to fix this hose, and it doesn't really have to look like the OEM part. Maybe a straight flexible hose about two feet long would do the job. It could be P-clipped anywhere convenient, as long as it can't rub anything important like the drive belt or pulleys (my wife's car did that to a steering hose ).

I'm putting the car back together now, so I'll soon find out whether I've trashed my ABC pump into the bargain!

nick

haoz129

Nick,

Great job removing and fixing the damper,.
Thanks for Drewk88 and your suggestion, I'll get a 72 teeth wrench for sure.

You guys are amazing! Keith replaced his pump, Drewk88 thoroughly tested the ABC and made his perfect, now you fix the damper.

Yes, hydraulic part of the ABC is no complex than other industrial hydraulic stuff. Your fix will definitely serves you well.

You pointed out in Drewk88's thread that I said ABC is a great system.
Yes, the more people understand the ABC the more will agree with my opinion.
We learn it, we understand it, we maintain it, we enjoy it, we love it.
Good attitude guide us doing our hobby in a professional way.

Have a great weekend!

Howard

haoz129

Your input makes me think the material of the hose is matter regarding " harmonic and resonace effects".
That means when we go Nick's method, the hydaulic supplier should consider this is a damper rather than a regular hose.

Thanks for your research.

Howard

drewk88

Yes Howard, precisely.

So an all metal hose wouldn't do, it must have the rubber sections.

But here's what I really like about Nick's fix; there are other lines in the system which have rubber sections, perhaps more for flexibility than for damping effect. And we all know these parts are not only expensive, but in some cases very difficult to change.

Well, once any hydraulic line (having a rubber section) was removed, repaired in this way and re-installed, if a subsequent failure of that line were to occur, it might be possible to effect the repair by replacing only the rubber section of that line without having to remove the entire line. That could drastically reduce repair time and difficulty, and of course, cost also.

In fact, it may well be that even the initial failure could be repaired without removing the entire line. Cut out the rubber section with a tubing cutter, install the compression fittings in situ, then go to your hydraulic shop and have the flexible rubber section made to length and install it. I may try that on my pulsation damper since only the end section is damaged, just where Nick's was.

I would guess that failures in the metal sections of these lines are practically nil.

Welwynnick

Drew, in hindsight (sigh....) I think you have a point there. Perhaps I could simply have cut off the failed connection in situ, and fitted a section with a compression joint.

However, that idea wouldn't have come about unless I'd removed the vibration damper in the first place, but its worth bearing in mind for the future.

I've now re-fitted my repaired damper pipe today (fine-tooth wrench earned it's worth), and I'm working on bleeding the system, and I have a cunning idea...

Edit:

There's a clear consensus that to bleed the ABC, you need to pressurize the fluid reservoir to prime the pump - otherwise the pump won't suck up the oil (for some reason). So I was wondering how I was going to pump up the reservoir... Since I now have a removable blank at the end of my damper, and with the serpentine belt still off, I thought I'd fill the reservoir and try to get oil through the damper simply by spinning the pump by hand. Maybe by turning it relatively slowly, I could prime the pump? No harm done if it DIDN'T work, but it would show that the pump WAS primed if it DID work. Does the logic make sense?

And what happened when I spun the pump? Well - after a little while - oil came out the end of the damper! I pumped it by hand for a while, until I was happy that the pump and damper were full of oil, then I closed off the termination at the end of the damper. I was happy with doing that, as it gave me confidence that the pump was primed. Then I filled up the reservoir again, disconnected the return pipe, pushed a few feet of clear PVC tubing into the end, and started the engine. To my relief, oil spurted out of the pipe straight away, and I ran a few litres through to flush the system. I wasn't brave enough to fill the reservoir continuously while the engine was running; I just started and stopped the engine a few times. The cold engine was idling fast, and the reservoir seemed to empty quickly. I was pleasantly surprised to see that the oil I was flushing out was clean, clear and green. So four litres later I stopped the engine and closed everything up.

So, very pleased and quite confident with a day's work.

Nick

kraut56

Quite an interesting read of the Mr. Vetter/Seidl paper!

I have a fair experience on the design of high pressure (3000 psi) aircraft engine driven piston-type pumps and their plumbing.

What is critical is the length of the pipe/hose, as too short a length will - due to the pressure ripple effect of the pump output - create an "echo" effect back from the next component. Thus, when this "echoing" effect takes place, it will actually augment the ripple and or spikes, depending on the flow/rpm conditions at the pump, which can easily exceed the design specs of the plumbing and the pump(!). The pressure/flow/ripple conditions can vary enormously over the engine speed range. Therefore designers are careful in surveying for pump ripple effect during design and testing.

Nice to see everybody involved here - Happy New Year.

drewk88

Nick,

I had considered researching the various hydraulic lines' sizes, threads, fittings etc. to see if I could find off the shelf non-OEM replacements. I figured it was a long shot, and so never put much effort into it.
For whatever reason, something so simple as what you discovered never occurred to me.
I guess it's like the Korean proverb; "It is very dark at the base of a lamp".

During my pump replacement, I was wondering about priming the pump by hand, but I had already put the belt and shroud back on, and I hadn't noted the direction of rotation. Glad to know another good alternative method now. I had bought an assortment of rubber stoppers. After removing the return hose from the large reservoir cap, I used a small stopper to plug the plastic pipe on that cap. Then I used another stopper with a hole to plug the dipstick cap hole. My blowgun nozzle tube fit nicely into the stopper hole, and I cranked the regulator on my air compressor down to about 12 psi. Then I did as you did, running the engine until fluid came out from the return tube. Then I depressurized the reservoir and proceeded to flush the system.

As kraut56 mentions, the dynamic pressure interactions within the hydraulic systems are quite complex. Incident and reflected pressure waves of varying frequencies and amplitudes, it is very much like what I encounter in my work as an RF Engineer dealing with RF transmission lines and antennas. The design of this pressure damper, being a long elastic tube, may be very important. It may be to give a more "broadband" damping characteristic compared to a spherical damper, because of the wide range of RPM over which the pump must operate?

Could you tell us what is the official size of the compression fittings to fit the metal tubing?

Let us know about your first test drive!

kraut56

Incident and reflected pressure waves of varying frequencies and amplitudes, it is very much like what I encounter in my work as an RF Engineer dealing with RF transmission lines and antennas. The design of this pressure damper, being a long elastic tube, may be very important. It may be to give a more "broadband" damping characteristic compared to a spherical damper, because of the wide range of RPM over which the pump must operate?

drewk88: Yes, there is a lot of similarity in RF transmission and microwave guiding to hydraulic power transmission.Actually, the damper should be an integral part of the pump or pump outlet, but that makes the pump more bulky and more expensive. A simple length-tuned hose or pipe is obviously a lot cheaper.
Note that an entirely different subject would be the acoustic or noise problems. Sometimes those, although different in severity, require different solutions, or can create new problems such as discussed in my previous post.

Just the rambling of a retired aerospace engineer.

Welwynnick

Away from cars, I'm also very interested in audio systems and RF engineering. I used to work in EMC and Satcoms, I was an audio reviewer, and make my own speakers. I also research RF effects on digital audio equipment in my spare time.

I too was struck by many of the similar concepts between hydraulic power on the one hand, and RF and audio systems on the other. Propogating and standing waves, impedance, terminations, reflections, that sort of thing. It did occur to me that the vibration damper might be a tuned stub, though I doubt its as complicated as that. Maybe there's a hydraulic equivalent of VSWR?!

Anyway, if you have a look around at the different types of ABC pump, you can see that the W216 and W221 use a pump with an integral damper. It seems to me that the damper pipe was a relatively late addition to the first ABC systems, as Mercedes were wrestling to deal with all the development issues. With the benefit of hindsight and development experience, they designed-in the damper in the next generation pump.

In reply to Drew's question - I don't know the size of the compression fittings, I should have asked at the time, sorry.

I'm hoping to back on the road today.

Nick

kraut56

Anyway, if you have a look around at the different types of ABC pump, you can see that the W216 and W221 use a pump with an integral damper. It seems to me that the damper pipe was a relatively late addition to the first ABC systems, as Mercedes were wrestling to deal with all the development issues. With the benefit of hindsight and development experience, they designed-in the damper in the next generation pump.

No - didn't look at those since my recent W220 Mistress acquisition has not given me any real problems. For the newer pumps: Yep - done that, been there. Bet you the new generation pumps also run quieter!

Enjoyed this!

PS: you should be able to measure the pipe size od in mm; the hose and fitting size will be accordingly

Welwynnick

Lessons Learned

I drove my TT to work this morning with some apprehension, but no leaks or alerts. It was off the road for a long time, but next time will be different. My rule of thumb is “half the time the second time”, and that’s probably conservative. I now have a spare car which I can use whenever I want – but should I have to?

This is my fourth W220, and the third with ABC. Previously, my approach to dealing with ABC had been to cross my fingers and hope for the best. But I’m rather more confident to diagnose and tackle any problems now, rather than throwing a bag of money at a dealer. Things like pumps and struts will always be expensive, but many faults are readily repairable. And you have to accept that they WILL happen.

I was working outside, to give me better light and more space, but this was a mistake. The weather wasn’t great, and that tended to keep me inside, rather than getting on with it. I’ll use the garage next time, and I’m still planning to get a four-post ramp soon. I would positively look forwards to working on cars if I had one of those. I never realised what they cost before, and wish I’d got one ten years ago…..

Since the car was nose-down on one wheel, I’d assumed that the problem was with the valve assembly, and didn’t notice the obvious fault at first. If there was a fault upstream of the control valves, I assumed that all corners would be low, rather than just one. There’s a lot you can do to manage ABC and diagnose faults, but it still pays not to jump to conclusions.

Removing all the parts necessary to get full access was half the game. I went overboard and removed all the wheel arch liners and the front bumper. (This was partly out of curiosity – I had long wanted to see if I could squeeze a larger charge cooler radiator in there) The trick is to know what to remove and what to leave. In general, DON’T lift the engine, but DO remove the fan and drive belt. The oil reservoirs and coil pack can stay put for the vibration damper, but probably need to come out for the ABC pump itself.

Finally, I have to confess that my ABC did give me some advance warning, and I’d stuck my head in the sand. There was a small leak at the front, and I should have done something about it. I lost the use of my car for a few weeks, but it might have been worse; I could have been on holiday with the family. In future I’ll inspect everything closely and act on advance warnings.

Nick

Welwynnick

There have been a couple of other issues with my car that I'm going to do something about now. The front brakes are heavily worn and corroded, so I'm going to replace the pads and discs (I think you call them rotors?).

The rear suspension struts are also leaking oil, so I'm going to take them out and have a look; maybe replace them. I might have a look at the rear subframe mounts while I'm there, too. Is anyone interested in seeing pictures and description of what happens?

Howard, this should be in the spirit of what you started, but I'm mindful of going off thread. This is your thread - are you happy for me to post here, or would you prefer that I started another thread? Happy either way.

regards, Nick

PS. Better get some more Pentosin!

haoz129

No problem Nick, please post your procedure and pictures here.
I will update the index (page 2) to reflect your previous and future posts too.

Your experience about fixing the damper are great, . It definitely will benefit other members and me as well.
As there isn't much works on my car so I'd like to extend the purpose of this thread.

Thanks for your contribution!

Howard

haoz129

Check coolant or top off coolant should be no brainer for every driver and for any car.
This was what I believe until I need to do it on the Mercedes.

Pretty cold in Canada winter and I got the white coolant alert today. During cold whether coolant will contract a bit and I think it is normal. The only thing I need to do is to top off the tank and make sure it reach the proper level.
Even kid can do, right ? But I found that is impossible because I cannot find any mark in the tank indicating the proper level. For my Volvo there are Min and Max lines on the tank. Never ordinary for a Benz.

After searched a while I found the official information: Different MB has different mark to use when come to fill the coolant tank. For W220, when you see the tank, it is the boundary that the black and white halves joint together indicates the proper level.

Now it becomes straight foward and I adjusted the coolant accordingly.
Please keep this piece of info in case you haven't had a chance to check your coolant.

Thanks.

Howard

wallyp

Reading thru this thread is interesting...

A thought occurred to me concerning the dampener section. Please remember - I don't have ABC, know little of hydraulics, so not being hampered by facts, I can discuss the subject freely. Is there any possibility that the dead-end section of the hose should not be bled, but should instead contain air as a small dampener/accumulator?

haoz129

I'm afraid you are right.
The damping effect will be totally different for a damper with air than a damper with fluid.
Physics is fluid cannot be compressed. That's how hydraulic systems work.

Thanks for bringing this up.

Howard

haoz129

Last January I was wondering about this issue during the test drive.

"I had few occasion can't start the engine when I am not in the driver seat. The engine cranked normally, just didn't start (I was using the SmartKey by turning Starter Switch). But as soon as I seated back, the car did it effortlessly then sang happily."

I have never had any instance like that after. So let me clear it up.

Actually the reason is I didn't know the touch-release way MB design their ignition/key system.
I use to hold the key in start position until my volvo start. And I so use to the timing, 2 seconds is just right to start my volvo.
So when it came to start a Benz, the computer passed the control to me as I was holding the key more than a touch/release, but the 2 seconds I gave it to start was just not enough. That's the whole story.

Now I just turn the key to III and release so the computer control how much crank is needed to start the engine. Not a single miss.

Good night.

Howard

haoz129

All,

It's been a year since I notice this. Just as everyone mentioned there is no issue in the trany.

Conclusion from this case: Small aluminium flakes are from manufacture process. Filter did the right job catching all metal shavings.

Thanks.

Howard


Original thread discussing this topic:
https://mbworld.org/forums/s-class-w...on-filter.html