Driving at about 65 mph last evening, I heard a loud boom, and the red ABC waning came up, and I could see oil trailing behind me on the drivers side. I guessed it was a hose and I drive about 4-5 more miles at low speed, but very concerned about burning the ABC pump up, then had it towed home.

Sure enough, blown hose in the LF wheel well (see picture).

No problem to replace the hose but, I am wondering if it was just a 24 year old hose, or if the pressure control valve is problematic too? This hose (smallish) must be a pressure line (vs. larger Low P return) and seems to go into the manifold there with the relief valve (pressure control valve) in it (see pics). About 2 years ago when I was sorting out the system (all new accumulators and replacing a strut and the rear valve block, flushing the system) the return hose just in front of the blown line in the pics, blew to at that time, I never figured out how that line became over pressurized? (maybe it didn't ?) That line gave off a large boom too and I assumed it was a pressure line or became over pressurized. That led me disassemble and inspect that relief valve thinking that maybe the spring loaded poppet was seized or was otherwise sticking.........it was fine (and I'm an old aircraft hydraulic and valve engineer). If I recall I was then able to see the system pressure in DAS.......and it was normal (can't remember 1500 or 2000 psi. And it appears taht the blown P line feed into the manifold, then the fluid passes over the relief valve and out to the return (Low P) line noted above. The system has worked fine since.






So, I'm seeking others experiences in this regard. Do I have my facts straight? Just a new hose? Or a need relief vale too? Should I replace other P hoses too??? Are some hoses more prone to fail? Thats a lot of hoses. And concerns or suggestions about re-starting the system? Or just fill and let it self bleed?

This is a car that I occasionally drive cross-country......places that are along, long way from my garage or any garage that go farther the US mad pickups. So, I don't want to have this occur on a trip like that. But, a fantastic long distance GT, so I can't resist!!

Thanks all in advance
MK19

 

So far I think just a new hose. I don't know my hoses well enough yet to know where the other end is, but hopefully not to difficult to remove the hose. An alternative to a new hose is to take the old hose with both ends to a hydraulic repair shop and let them make a new hose for you, reusing your ends.
Even smaller towns have hydraulic repair shops to serve trucks, construction equipment, farm equipment and such.

 

Hydraulic shop is fine re-using the ends.

Swap your fluid, filters and all accumulators. From all I know, blown hoses only come when accumulators are failed. Without that dampening effect (or with sludged fluid) is the only way you get pressure spikes that are sufficient to blow hoses. Some may disagree on this point, but if you think you'll get blown hoses with all fresh fluid and accumulators then that means don't own the car.

Accumulators are good for 10-15 years, 100k to 150k miles, so once in your ownership maybe twice. Fluid and filters I do every 3/30 or 5/50. So far either interval has been fine.

GL

maw

EDIT ... I didn't see you had all new accumulators. I'm pretty sure the fluid cleans and lubes the pressure relief valve so I'm not sure what that's about. But I don't DIY this system so sorry I can't be more helpful. I will say though, I don't see any mention of filters with the accumulators and fluid.

 

Besides age, the main reason for a hose to blow is because the accumulator responsible for absorbing the fluid shock is dying. Seeing that you have extensive experience in hydraulics and also replaced those parts, I think Id start with just the hose, or hose repair as well. After you replace it you can always monitor the system in Star/DAS if you have it.

 

Yes, I understand the role of the accumulators observing pressure spikes. And I replaced all 4 accumulators (or was it 3?) about 2 years ago. When I had at lease one bad one, which resulted in an ABC warning when going over bumps. That issue was resolved by the replacement accumulators.

There is an accumulator right next to the hose failure. It's located on the pressure control valve manifold behind the LF wheel. Could it have failed???

New OE hose arrives later today. FYI, the local hydraulic hose houses don't handle metric sizes.....maybe in a big city, but not in rural Colorado.......all farm stuff.

Thx.

 

Have you seen this?

https://cdn.webshopapp.com/shops/352...-watermark.pdf

 

Yes, but thanks Balti
It's very informative but I don't think it discusses blown hoses.......but let me know if I've missed something there.

Has anyone seen a blown hose?

MK19

 

It doesn’t discuss blown hoses specifically, but if you search the word blown, it will talk about blown accumulators and the pressure variables. I never had a blown hose specifically, just leaky O-rings at the connections…which I replaced.

 

Thanks again for Reminding me of this Balti.

I hadn't reviewed it in some time and after doing so I have a number of things to check after replacing the bad hose, namely the small accumulator on the relief valve block that the bad hose feeds. This is the pump pulse damper and if its blown, then the pump would likely have beat that hose to failure. It was replaced in mid-2021 and less than 8k miles back, (car is an '03 with 81k miles) but it may be bad as I think I heard the Humm described in that paper. Plus I can just poke something in this accumulator and see if the membrane is present and firm. And I'll feel the hose in and hose out as described and expect to find a marked difference in the pulses if the accumulator is good.

I'll update my post on any findings.

Best, MK19

 

I installed the new hose today. but before I did, I pulled the accumulator/pulse damper from the Relief Valve Manifold and poked around inside. I has a little metal like a rivet or such inside the port, likely to keep the membrane from blowing out of the port. It was solid when I pushed on it, and as it was still quite new, I decided it was ok and reinstalled it. For future reference, the bottom end of the hose/tube connects to a "T" underneath that's next to the left Cat, so not to bad a job..........of course as everything was oiled down, it was messy.

I was planning a fluid change anyway, so I set that up and filled the reservoir. Worried that I could have damaged the pump on my short few mile drive after the hose blew and the reservoir had been pumped dry, I also wanted to monitor the flow. It was slow to start pumping, and i started and stopped the engine in short intervals until choaked down a few quarts of oil, and once it did, then I finished the flush as normal. Put in a new filter, checked for leaks and then tried to feel the two pressure hoses at the Relief Valve Manifold to sense a difference in pulsation as suggested in the ABC Specialists paper. Whatever differences were there were pretty subtle......so inconclusive on that.

System pressure looked normal at about 198-195 b, and the system seems just fine.

So what did the hose blow? Possibly just old (22+ years), or maybe the accumulator/pulse damper that I replaced had been bad for some time and that fatigued the hose? Hope it holds up. Thx all for your inputs here.

 

Great work, congratulations. 22 years of a hose running close to 3000 PSI, hard to complain. New one should last at least 7-10 years, and very likely twice that.

 

Old age, they’re all likely seeping/weeping at this point.

find a good shop to go over all your hoses and they can predict which one will go next.

my shop told me one that could be problematic, I totally forgot it’s been a few years now.

 

So I just had a similar situation happen to me. One difference was I was sitting at a red light and heard a little boom and a small cloud came from my front wheel well and ABC warning light came on. My car is a 2005 SL 65. I drive the car home about 3 miles with no additional noises and car drove close to normally. Car is leaking fluid along the divers side. I haven't had a chance to look at it yet but can anyone suggest a course of action? I was just leaving the MB dealership getting a new battery as the price difference wasn't that much compared to auto repair stores. I inquired about getting the ABC system flushed and they didn't have anyone there who understood how to work on the system.
Any suggestions??

 

If you aren't into doing the work yourself, I'd look for a good Indy shop. BTW, an MB dealer who can't service ABC is a joke dealership........I'd stay away or find another if you don't prefer an Indy.