I just finished up replacing the high pressure hose that runs under the engine from the pump to pulsation damper on my 03 SL55. Thankfully it did not explode on me, but developed a large leak just sitting at home.
Along with a fluid flush, I decided to replace the 1/2” Magnefine ATF filter I installed inline of the ABC return line to reservoir approximately 5 years and 30k miles ago. Attached is a picture of the cut open filter (I used to a pipe cutter to keep it clean, no shavings)
There were no large metal particles to be seen (thankfully) The black residue on the white towel below the magnet is what wiped off of it, which I presume is metallic dust that circulated past. The 3 micron ABC filter might have caught a lot of the same residue but for $20 this seems worth it. Happy motoring.

 

Where did the line develop the leak? I would suspect that the leak occurred due to age and pressure but Mercedes said these were lifetime systems and we see a lot of theses failures. Maybe they should back them for lifetime like the SBC!

On another note, how did you fix the line?

 

Seepage around a crimped fitting leaking into and through the heat insulator.
Definitely an age+use issue, it sees more pressure and pulsation than any other hose in the system and the car is nearing 20 years old! I’m just glad I caught it at home and not on the road (there was a pool of green ABC blood under car and through splash shield when I moved it from garage for a warmup)

I fixed it using a compression adapter on the hard line from pump and also routed the hose differently straight to the pulsation damper. I eliminated the banjo with a port fitting and have JIC couplings on either end for easy future hose replacement. I did this as a hose I replaced 5 years ago began seeping and needed to be replaced *again* but was put in with compression fittings. I was uneasy about having to reuse them so didn’t want that on this critical section.

 

I am just about to replace this hose too.

Would you have any pictures of the fittings you used?

Specifically the port fitting: is this a 90 degree piece that replaces the banjo?

I want to copy your work and would much appreciate more information.

Tom

 

I have a couple of pictures attached. The inlet fitting on the pulsation damper/pressure regulator assembly is just metric thread using a banjo bolt, so I used an adapter. Male metric port with o-ring boss seal (ORB)(m14x1.5 thread) x 3/8” JIC. I used a straight fitting and a 90° jic fitting on the hose. Either should work, I wanted the straight fitting so I’d be less likely to screw up the assembly for orientation. Compression fitting is right by the crank pulley (which I may need to replace as well, little wobble going on)
Hose loops back, under front valve block, up and over the wheel well and down to damper (03-06 model)
You will want a 9 foot total hose length for this run. It is possible to just follow the factory routing as well but I wanted to keep the hose away from the heat. Tons of room for this.




Seems to be working great!

 

Ah. I get it. You had the hose made up with a 90 degree bend in the metal section.

Those JIC fittings are actually designed to be screwed on and off many times, unlike the compression fittings which appear to be designed to be installed only once and not repeatedly removed and replaced.

This will be my first foray into the world of hydraulic lines and fittings.

After I do the main hose, which I will do in this way, I plan to replace every soft hydraulic hose in the car.

THANKS heaps for the info.

Tom

 

The easy future replacement is exactly why I wanted to incorporate the swivel JIC fittings on this critical hose section. As I mentioned before I had to replace a section I had already used compression joints before. I had a slight drip from each after installing the new hose but after cranking down to near thread snapping tightness they are okay. ...works, but I didn’t like it so from here on I am going to try to use removable fittings where space allows.
I’m thinking I may do the same as you and continue on the rest of the soft hoses. At least the other high pressure lines for now. They look perfectly fine but that doesn’t seem to mean anything! Could be degraded from the inside out.

Forgot to mention before the hard line from the pump is 12mm tube for the first section where the compression fitting is. It necks down to 10mm closer to the pressure regulator/damper. Most of the system is 10mm tube.

Good luck with the repairs. This is a pretty easy one to work on as you have plenty of space! Let me know if you have any questions.

 

I sidelined this thread; you posted about the magnetic filter.

Nonetheless replacing the critical, aging soft hydraulic lines will no doubt be of great interest to users worldwide.

I am about to make friends with my local hydraulic supplier. The two lines that exit from the pulsation dampener appear more of a challenge; perhaps the hydraulic shop can replicate the bend in the metal section. I will take them off pretty soon and get some advice. Since presumably the pressure halves at that point they may be less of a threat but as you say, this is an age issue.

Mine are both nice and dry but the input hose is seeping a bit.

Another potential issue I thought about was that the original line routing is probably pretty good in terms of heat insulation, in that it runs under the engine and away from the exhaust, with insulation on the under-car section. Re-routing the line in front of the engine may expose it to more heat that it should receive but I will cover that section in heat insulation. It's not clear from your photos if you did that.

I will document my work. Stand by.

Your wheels are stylish. Classy. They look like they grew there. They're not factory are they? Some of the wheels you see around...

Unbecoming. That's being charitable.

 

I replaced my main pressure line in the same way and it works perfectly - no leaks.

But. I have a noticeable vibration at around 1500 RPM - sort of like the vibration I had before I replaced the pulsation dampener but not as bad.

The original factory hydraulic line has soft sections which are very flexible. The new hose I got is 4800 psi Aeroquip and it's very stiff. So what I am wondering is if the new hose is too stiff, causing the vibration. Does anyone have any insight into this?

A secondary thing which I just noticed is that the banjo fitting that goes onto the pulsation dampener valve block is attached with a bolt that contains a one way valve. I removed this fitting as mentioned above. Could the absence of the one way valve in the bolt be the cause of the vibration or does this valve just stop fluid draining back when the car is stopped?

With thanks in advance

 

The factory hose sections on my car were Aeroquip, I don’t recall the pressure rating but it’s likely similar. I did use a more flexible 100r16 hose in place of the more common and stiffer 100r2. What spec hose did you use? I don’t recall what the factory hose was marked, but I did notice it was very flexible and soft (for a hydraulic hose) as you mentioned.
Even still, if you followed the same run I mentioned you have several more feet of flexible hose section than the factory line. I haven’t noticed any vibration issues yet, but I’ve only driven the car on a couple short runs since then. It has idled plenty with no issues. I installed new motor mounts just last week. It is silky smooth now so I’d definitely notice!

More likely you just have vibration from the hose itself (or a fitting) vibrating against the body somewhere. I just used some split loom around the hose to prevent this, but heater hose or similar around the hose wherever it can contact the car and attachment points would be better. Note the large, rubber isolated clamps used by Mercedes on the hard tube sections.

I noticed the same valve assembly within the banjo bolt on mine. It appeared to be white plastic? If so it definitely can’t be a one way valve for the pressure we are dealing with. Mercedes just refers to it as a “hollow bolt” Any time the pump is running it is pumping out high pressure through that line and fitting, most of which getting returned back by the damper/pressure regulator assembly. If it is a check valve i could only think it’s purpose would be to keep fluid from going back when the car is OFF. In this scenario all the valves are all closed anyway, but there is residual pressure held in the system for several minutes by the accumulators.
Perhaps this helps keep the accumulators pressurized for longer after the car is shutoff? Or helps to keep the residual pressure directed to the return path rather than the accumulators quickly pushing it back to the pump. I don’t know for certain and can’t find anything about it.
If needed, We can both easily re-incorporate it by using the factory banjo bolt fitting along with an off the shelf metric banjo to JIC adapter and crush washers. This was actually my original plan before I saw I had enough space for a direct fitting into the block (before realizing the bolt had something inside it)

 

I'm getting to know my hydraulic shop well.

My hose is Aeroquip GH781-6 and wow it's stiff. Could it possibly be that the grade of hose was somehow incorporated into the design as a vibration dampening feature? Logic tells me that hydraulic hose should not be expandable.

The vibration - I will check the run. Thanks.

I already bought the fittings to reinstall the banjo. figuring that one way valve has a purpose. I carefully cut off the crimp; underneath lies a section of standard 3/8" steel. The compression fitting I bought will go over that.

Plenty of room under the guard to get it all in.

 

Solved!

It was the one way valve in the banjo bolt. It must be fitted.

Super smooth now.

I have written up the entire job on a long post on the other forum: search Replacing the main ABC pressure line with custom made hydraulic hose and fittings

I don't know the politics of these forums and if external links are allowed. Surely we're all about sharing knowledge.

THANKS to all.

Tom

 

Looks good. Are those brass fittings high pressure rated?? I’m not used to seeing brass parts at these pressures. The high pressure hydraulic fittings I’ve used, compression or otherwise, have always been steel. Remember these parts can easily see 2500psi+
or are they yellow zinc plated steel?

 

You can eliminate most of those fittings by using just the banjo->jic adapter I mentioned earlier along with the stock bolt. I’ll do the same if I notice any NVH issues arise.

I’m still curious why you had a vibration/pulsation issue and mine is quiet, unless the hose type really impacts it that greatly? :shrug:

I was going to make a write up about my little solution after some more seat time but I guess I don’t have to bother! haha

you had asked earlier about whether Mercedes engineered the hose run into the system and whether it should be expandable. I don’t know about expandability but the OE hose was definitely quite flexible for this run. Mercedes did indeed purposely incorporate the hose sections in the manner they did to combat noise issues. In fact on some other ABC applications, specifically the V12 CLs where there wasn’t room for the long hose run, Mercedes used a dead end hose leg off the main line (using a double stack banjo off pump) as a super simple damper

 

Drock, I'm really surprised you didn't notice the vibration without the banjo bolt fitted. When I had it off, the hose shook and pulsed hard. Reinstalled, smooth as.

The brass fittings: I don't know. They're pretty chunky. Hard to imagine them blowing off, but since they came from the hydraulic shop I can only hope.

Re-engineering such a design has me nervous but so far so good.

 

Yes I wondered about getting a metric banjo adapter to JIC as you mentioned but my hydraulic shop told me they weren't available and I wanted to get the job done. I just searched on eBay and there they are...

Is there enough room on the side of the pulsation dampener valve block to get the hose fitting on to the banjo fitting?

Since I already had my hose made up I went the elbow route rather than a new hose. Overall needlessly complex but working perfectly for now.. The thick foam shield definitely provides a measure of NVH suppression.

Tom

 

Brass is a soft metal, but with enough heft the ratings may be fine. I only did a quick google search and only found a few options up to around 1000psi. I’d give your supplier a quick call just to confirm just in case. Hopefully a non-issue

Re-engineering it concerned me a little, which is why I wanted a little more seat time with the revised setup before posting about it specifically - but I’m glad you got the kinks in your install sorted. At its core it is just a hydraulic system which I’m plenty familiar with for equipment with my job. But in this application it obviously has to be more than just functional, it needs to be smooth and quiet too!

Nice work on the write up and I read you just did the motor mounts recently as well. What a pain, right!? Well one side at least.

 

There is sufficient space provided you stick with 3/8 jic fittings. That was a concern of mine as my original plan was using 1/2” jic fittings, but the clearance would have been tight to the block using the banjo adaptor which is when I thought to just lose the banjo entirely.

Complex or not as long as it works and doesn’t leak it’s all good. It’s not like Mercedes ever took the keep it simple, stupid KISS engineering approach with anything else on these cars

That was a good idea on the foam plumbing pipe wrap, I even have some around here but didn’t think to use it.

 

This is what happens when novices get on the case (me).

I didn't think about the pressure rating on the brass fittings. The hydraulic shop might have bothered to tell me. Anyway.

I just bought stainless fittings: 10,000 psi. Stand by. Thanks for the heads up.

I didn't find my engine mounts too hard. For such a common failure there was surprisingly little how-to on line, but it's really pretty easy. I took off the exhausts and jacked the motor up a bit.
I would have just lubed the mounts and spaces with silicone spray first to make them easier to wiggle back in though.

 

I took out those brass fittings; rookie mistake.

The stainless are unwieldy but work and don't leak. And they're rated to 10,000 psi.

See the updated post at the other site with the link above. Credit to dRock for the JIC fitting idea.

On now to the other critical hoses!

And how about a high-pressure magnetic filter to go in the main line?