SLS High Pressure hose. 1984 300TD - Page 2 - PeachParts Mercedes-Benz Forum

whunter · #16 02-14-2014, 08:32 PM

Repairing hydraulic hose for SLS hydropneumatic suspension on TD
Repairing hydraulic hose for SLS hydropneumatic suspension on TD

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firstdiesel · #17 02-15-2014, 01:49 PM

Agreed. The part/s I actually need is just the restrictors or orifice tubing. The rest of my setup is fine. I got the new hose and the ends are fine, so I'm almost home on getting the car back on the road.

The hydraulic shop I went to offered to cut a piece of ss tubing to use as orifice tubing, but I turned them down since I am not that familiar and wanted to stay with something from MB.

Should I have just gone that route? Is there a specific inside or outside diameter I should know so as not to restrict the flow too much?

Thank you whunter, those posts are helpful.

83TD · #18 02-15-2014, 02:29 PM

Quoting from the FSM 32-671:
"Starting May 1978 oil lines with throttle(orifice) are installed between the level controller and the two pressure reservoirs. This will provide cross damping of roller movements and avoid flow noises, knocking noises during deflection, as well as during deceleration following acceleration from low speeds."
If you do not know the history of your vehicle, it is possible that the correct damped lines were replaced with plain brake lines--I had a dealer do that on my car many years ago when I had the spheres replaced--he claimed that the threads on the factory lines had been cross threaded at the factory and could not be reused. Of course, he had no original lines in stock so substituted brake line. I replaced the brake line with the correct oem line and I could see that a piece of wire had been inserted into the oem line to provide the flow restriction and damping. Pretty high tech, even for Mercedes.
Further from the FSM:
"The lines with the throttle(orifice) can also be subsequently installed, make sure that a HP expansion hose with damper is installed on pressure oil pump, if not, subsequent installation is required. These HP expansion hoses are identified with an arrow-direction of flow- at rear connection. They are installed on all vehicles with diesel engine, starting 1978 also on vehicle with otto engine."
Hope this bit of history helps.
Peter

firstdiesel · #19 02-15-2014, 02:36 PM

Yes Peter, it does help. I did not notice any of the fluid lines being different from the greenish grey color they all seem to be painted with, but that doesn't mean that it wasn't changed at some point.

I am definitely missing the dampers inside the HP hose.

Thanks for the info

firstdiesel · #20 02-16-2014, 06:38 PM

John, sent you a PM

vstech · #21 02-16-2014, 09:41 PM

yup, I got the PM, I'm trying to get time to pick it up and confirm what's in it.

fahrvergnugen · #22 09-19-2014, 05:24 PM

Well,

I just rebuild my hose, and swapped-over the plastic inserts, all 31 of them. 30 white ones, and one red one. And I appear to have the noise that you are speaking of, a groaning that is constant and related to engine speed. I am really confused why it makes noise if I inserted the plastic bits as required?

Any wisdom here? I am searching for an answer.

TIA

firstdiesel · #23 09-19-2014, 06:03 PM

Hi fahrve,

I wish I did. I went up and saw John just to get the plastic pieces that mine was missing at the time. I have to say that it did quiet the noise I was hearing, but alas, it didn't go away; and of course it is still driving me insane.

Literally I have replaced everything else in the system except the reservoir and the pump. I got a used pump from John that I haven't tried yet. I'll probably switch that out tomorrow.

I have replaced the hydro shocks, air cells and rebuilt the ride height adjustment valve in the back as well. Of course, all of it did need to be changed, but that noise only got better with the use of the inserts. Only thing left at this point is the pump and reservoir and a plastic tank to hold the fluid just doesn't seem logical. If the pump doesn't do it, then all that is left is the tubing. I did check all of it under the car to make sure it wasn't touching the body somewhere, but it wasn't.

I'll let you know what I find out if I get a chance to change it out this weekend.

Todd

fahrvergnugen · #24 09-19-2014, 06:41 PM

Thanks, FD.

Here's the hose I used... Product Detail Page I am assuming it is the right stuff, he said it was good to 4000 psi.

firstdiesel · #25 09-19-2014, 07:28 PM

Here's the thing, there is an entire thread (don't have it off hand) that talks about the psi of the hose. Funny thing is, the one I got from John that I pulled off of a Euro wagon, I was able to cut through the OEM hose with a pair of razor type cutters like a hot knife through butter! Nylon (or some other cloth type of material) all the way, no stainless steel at all. That hose was intact, so I am certain that a stainless hose rated at 4000 psi will be perfect. I know that he went through lower rated hoses and they blew apart, so I went with his suggestion as well.

fahrvergnugen · #26 09-19-2014, 08:37 PM

Right... I had to cut mine apart to get the doodads out too; same thing, nylon something or other. Only thing I can think is perhaps the ID is different, and therefore the dynamic of the fluid is different and it makes noise? Or perhaps, one should re-bleed the system from the valve in the back so that air is released? Ultimately, I think the air would self-purge since I haven't cracked the rear part of the system... I am waiting to hear from biodiesel300TD on the seals to rebuild my valve in the back. Once I do that, I will install the spheres I have, flush the system and and bleed it.

firstdiesel · #27 09-22-2014, 02:06 PM

I have been told by more than one person that the system is "self bleeding". By just driving it around, or pushing down on the back bumper many times, will bleed the system.

Does the rear end "sag" or leak down overnight? Because if it doesn't, I wouldn't touch anything until it does, unless you are seeing a visible leak. I am not saying it shouldn't be done, but I have found that OEM parts working properly, are better left where they are.

firstdiesel · #28 09-22-2014, 02:12 PM

I changed the pump and it does sound much quieter than before, but it still isn't perfect.

I think you may be onto something with the ID. I am using an aftermarket hose that was on the car, got the pieces from John and just put them in. They went in remarkably easy and didn't bind on the sides of the hose in the slightest. My logic there, which has been known to be highly subject, is that if the pieces aren't tight around the side, they would allow some of the damping properties to be reduced thus making the sound quieter without getting rid of it completely. Good point.