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The new flexible hoses are terminated in 10mm compression fittings.
They're rather like domestic plumbing compression fittings, with copper olives that are compressed onto the outside of the mating tube with a screw-down bolt.
However, they're rather more robust to cope with the high pressure, and are completely reliable in my experience.
They are also removable, without having to remove the rest of the metal pipe, so if it fails again you can simply drop in another.
The connections to the car's equipment - struts, valves etc - are the OE connections. I don't think its feasible to replace those due to the tight geometry of the bent metal pipes close to the equipment. I discussed this a few times with my hydraulics man, and he said the metal pipe sections had to stay. Just the flexible sections can be replaced, and you need a short, clean section of straight metal pipe to connect to.
Obviously, the new flexible section needs to be a bit longer than the original section, as the repair section has to overlap with those sections of straight pipe. (If that's not obvious, this might not be the way to go for you).
Here are the links I was looking for:
Can anyone recommend a hydraulics shop that rebuilds the hoses and valve blocks , and their cost ?
They're a commodity. Use any well-established hydraulics/pneumatics shop.
I've been doing some research on hydraulics and hoses, trying to find out how long hoses are expected to last. The usual answer is that it depends, and very few people will stick their head out and give a figure. I only found a few guidelines:
The shelf life for a roll of hose (stored cool, dry and dark) is just ten years. That's without any terminations, fluid contact or high pressure at all, so there's no way an ABC hose should be expected to last that long in situ. Here's a data dump of some recent on-line reading:
Even knowing all the operating parameters of a system, it is still difficult to predict the expected service life of a hose. Probably the best tool to prolong life and predict failures is an adequate maintenance program. This includes keeping the fluid clean and visually inspecting hose for signs of abrasion, heat damage, and so on. Depending on the application, a simple visual inspection once a month is often adequate, with a complete overhaul and replacement of hoses and other components every year or two. On the other hand, if a failure would be life threatening, changing the assemblies every month would not be out of line. Keep in mind the associated costs and repercussions of failures, down time, and potential life-threatening injuries. It is better to replace a $100 assembly twice a year rather than spend thousands to clean up or make repairs from a spill.
Just as twisting can dramatically shorten hose life, so can excessive heat. Heat from external sources, such as exhaust components on mobile equipment, can quickly soften or embrittle the hose wall from the outside in. Therefore, it is important to keep hose away from external sources of heat. If this is not possible, manufacturers offer insulated protective sleeves to partially block heat transmitted to the hose.
An inspection of all of the hoses should be performed at least monthly. Signs that a hose is about to fail such as bubbling of the outer hose, loss of flexibility, cracks, discoloration or signs of abrasion are easy to spot. It is always better to replace the hose before it fails. If the hose fails during production, not only will production time be lost but it is likely that the ruptured hose will damage something else. Anyone who has ever witnessed a hydraulic hose breaking knows that it is not something to be taken lightly.
For construction equipment, hoses can be expected to last 5-6 years.
http://en.wikipedia.org/wiki/Hydraulic_machinery
The weakest part of the high pressure hose is the connection of the hose to the fitting. Another disadvantage of hoses is the shorter life of rubber which requires periodic replacement, usually at five to seven year intervals.
Generally, the following factors commonly contribute to premature hose failure: external abuse, rubbing & abrasion, twisting, stretching, over-pressure, over-temperature, fluid contamination and tight bends. ABC pipes are pretty well clamped and protected, but I bet the hoses in the engine compartment get hot. They seem to be the ones that fail first.
For critical applications, it seems to be the norm that hoses should be replaced at periodic intervals as a precaution. Agricultural and plant operators don't simply wait for some thing to fail, they perform preventative maintenance. Industrial hydraulic systems are usually designed with maintainability in mind, so the hoses have suitable fittings and are accessible.
Rather like brake pipe flexible hoses, in fact.
Nick
Last edited by Welwynnick; 06-11-2014 at 08:37 AM.
So my sugestion to Mercedes is, why not have cheap, simple, robust, removable fitting at the end of each flexible ABC hose, so they can be replaced like brake hoses?
It could be a flare fitting, which is robust, and can be made up in the field. Hydraulic connections are traditionally metal-to-metal, but increasingly often they have O-ring seals, like the ABC quick-release connectors at each strut (but do without the quick-release).
Flare connections are a labor-intensive method of making connections, but are quite reliable over the course of many years. Flared fittings are sometimes
thought to be more secure against leaks and sudden failures, and are often preferred for safety-critical connections, such as in hydraulic brake systems.
http://en.wikipedia.org/wiki/Flare_fitting
Flared connections offer a high degree of long-term reliability and for this reason are often used in mission-critical and inaccessible locations.
I've just bought five more ABC hoses for my car, and they're all much the same length. They have compression fittings, but I'd rather they were flare fittings. Actually, thinking about it a bit more, there's no reason why we can't make flare fittings ourselves. Cut the pipe, slide the nut on, flare the end of the pipe with a suitable 10mm flare tool (not ridiculous), and then you simply screw on a new hose. The fittings cope with multiple removals, so you can replace the hose as often as you like, and the pipes stay where they are.
So that way, Mercedes dealers (or any dealers for that matter) could carry a stock of cheap, industry-standard hoses that will fix most leak problems quickly and easily. And because its just the hose that would have to be replaced, the full length of the pipe doesn't have to come out
Doesn't that sound like a sensible approach?
Nick
Last edited by Welwynnick; 06-12-2014 at 08:03 AM.
I know what you mean. MB garages are as far removed from charitable organizations as you can imagine, but MB do need to ensure their cars are maintainable. I think they will go through a long and painful process with their best customers if they don't face up to the conclusion that the hydraulics industry presumably learned the hard way a long time ago.
There are lots of companies that make custom hydraulic hoses, and they all have standard terminations, meaning that the vast majority of hydraulic hose applications allow quick, cheap and easy replacement of hoses. Replacement hose assemblies are generic rather than specific, and the two-wire, 3/8" hose that MB use is perhaps the most common of all. Its cheap as well - a couple of bucks per foot or something like that.
I think its got to be a question when rather than whether MB face up to teh inevitable
Hope you don't mind me resurrecting this post... Hoping someone has been here...
Found the info herein invaluable and think I on my way... No novice... have fixed my Ferrari, Jag and Porsche many times, but have yet to touch this mb
I have a 2007 S600 w/ 60K miles... Looks to be the same or similar ABC/ power steering system as the w220. I didn't find much on the W221 forum...
Here's what happened.... Pulled out of the garage, after a few FEET, battery symbol came on and steering went dead. Backed to the street and realized things were not getting better.... pulled back in the garage and shut her off.
Looking in the engine compartment, can see lots of "green oil". Mainly on the serpentine belt and dripping on the belly pan and depositing on the floor. Maybe 6 oz of oil on the garage floor, which never had a drop before...
Fluid looks to be coming from driver's side, front of engine right above the hydraulic pump. Just a wild guess(WAG), but maybe the battery light and loss of steering is the loss of friction on the serpentine???
I haven't started her again to see where the fluid is coming from...I'm waiting to get some synthetic ATF to top off the P/S and ABC reservoirs. There's still fluid in the reservoirs, with the engine off, but I don't want to risk damaging the pump or getting air in the system.
Any input would be greatly appreciated.... Mark on South Padre Island, TX...
Here's a pic of our S and an image of the system I got off this post, if that can help anyone explain:
Not necessarily a burst hose , but a good possibility
You need to try to see where the fluid is coming from - there are many covers underneath and it can be difficult . If it's coming from a hose there's your culprit.
But sudden leaks like that can be from the abc /ps tandem pump , a reservoir burst , or a failed accumulator (which sends the fluid spraying out the top of the abc fluid reservoir )
Since you said the steering became difficult and not that the suspension dropped , I'm betting a power steering hose failed , but it could also be the ps side of the tandem pump
First thing is, don't run the engine until you've checked that the ABC reservoir is full.
Then find the oil leak. My money is on a flexible hose, but see what you find, and don't jump to any quick conclusions. Its easy to get it wrong initially.
Thanks again....I know there's some controversy here, but I'm using Valvoline full synthetic ATF as the replacement fluid.
Anyway, the hose that runs over the top of the pump (and then makes a U-turn for some strange reason) split close to the engine. It runs from the pump to what I think is the pressure reservoir. Will work on getting it off and see if O'Reilly's can fabricate a new one.
Oreilly cannot repair ps hoses. A hydraulic shop (forklift shop) might be able to, but If it's just a ps hose leak , get a new hose from
The mb dealer and refill with pentosin
If you Change to valvoline atf you'll have to do a complete flush to avoid mixing fluids and who knows what problems running atf might cause . The abc/ps system ain't cheap and ruining it over saving a few bucks on a few liters of pentosin ain't worth it
Glad you've found the leak but id definitely run Pentosin, or equivelent, in there rather than any other type of fluid. From what i can gather most other fluids dont take too well to that kind of pressure.
While the conservatory over full synthetic ATF over Pentosin still looms (VW folks have been using the change for years... and I've never heard a problem with the substitute....), I'm incline to stick with CHF11s.
That said, I've got the offending hose off. I thought it would be a simple matter of using the existing connections to fabricate a new hose.... Not so...
O'Rielly's will not use the existing original fittings to fabricate a new hose (liability issues, they say). And needless to say, they don't have the correct MB attachments.
I then looked at 10mm compression fittings and stock hydraulic hoses, as suggested herein... Not available in South Texas and most of the country(the 10mm compression fitting) , as I've been told.
And then it occurred to me, How much pressure do these hoses need to withstand? 3000PSI, 4000 Psi??? Off the shelve stuff doesn't seem to cut it???
My conclusion is, I'm left at mercy of the dealer price.... which, there appears to be no competition, and no internet quotes.
Nearest dealer is +50 miles away... And, I don't know if they have the hose I need in stock. I can only call them tomorrow.
There are lots of different CHF-11S. They're all a similar price, and maybe they're all manufactured by Pentosin, and marketed by other companies, but I think that's unlikely. They all have very slightly different physical properties.
There are other types of CHF as well, like CHF-202, which is not miscible or interchangeable with CHF-11S according to the Pentosin data sheets.
I really wouldn't get hung up on oil. You could probably use an ISO 32 hydraulic oil, which is cheap as chips. There's anecdotal evidence that works OK, but would you want to risk it? These days I tend to buy all my oil in large quantities from ebay Germany.
Here's a pic of the hose that burst. 3 screws and a couple of brackets to remove. Not the hardest job ever, but not the easiest either. Not much space to work in... Also, can't understand why the hose has to make a U-turn over the pump???
Special ordered new one (none in stock) from San Juan MB(TX, not Puerto Rico). About 500 clams. Got the Pentosin Chf 11 from Amazon, $85 for 5L. Both should be delivered Tuesday.
Sorry for all the shadows in the pic. Beautiful sunny day here on South Padre Is.
Thanks for the tip on MBpartsworld. Already ordered from dealer here, but tried to do a price comparison. Couldn't find this hose on their website.
Any tips on filling the system when I get the new hose on? Anything I should know or just fill and start? I have 5 liters of fluid to play with but, I don't have MB Star.... yet...
04-26-2014, 04:12 AM
