Auto Level Suspension - PeachParts Mercedes-Benz Forum

smartin · #1 01-27-2003, 11:31 AM

1985 300 TDT wagon - Started to investigate why system does not work. (I was guessing a leak - but not at rear - no signs) Put MB susp fluid in reservoir - started engine later in the day noticed level was at bottom of reservoir. Put in a little more fluid - started engine let it run (parked) saw leak under engine - could not see yet where it was originating. Puddle was right under engine just front of oil pan. Anybody know of a "common" leak poit on this system? Thanks all.:

lrg · #2 01-27-2003, 12:24 PM

I'm not sure there is a common leak area. Just be sure to continue to use the proper mineral based fluid or you will start seeing leaks EVERYWHERE. If this car is new to you worst case is the prior owner may have used the wrong fluid. More likely, one of the rubber hoses has dried out and needs to be replaced. Start at the pump and work back toward the rear. Be sure to flush the system after replacing a hose. If the system still doesn't work do a search and you should be able to find all the info you need. In a nutshell though if the system holds fluid then the usual points of failure are (generally in this order):
1. accumulators
2. self leveling valve (at the rear)
3. shocks
4. pump

Good luck.

smartin · #3 01-27-2003, 11:49 PM

Thanks for the info. Will need tor trace lines under car at engine - there are 2 ? Is this correct? Does anyone have a diagram or drawing that I can look at while I am waiting for manual?

Aaron · #4 01-28-2003, 12:07 AM

The pump that pressurizes the hydraulic system is at the front of the engine, towards the driver's side. It's a round radial-piston type pump. There is a flange and a gasket between the pump and the engine block and when the gasket goes south, the pump will leak INTERNALLY. If one of the pressure hoses is bad at the pump, it will leak EXTERNALLY. Make sure this is in fact hydraulic fluid that you're seeing because it's not uncommon for the pumps to leak internally. This will then cause hydraulic oil to be sucked into the engine oil circuit.

lrg · #5 01-28-2003, 12:54 AM

There are two lines, a main pressure line and a return line. FYI, the fluid is filtered on the return line as it re-enters the resevoir. If you trace the lines you'll find most of it is metal. Be sure the fittings are tight as those can leak too. If I remember correctly they cross over to the passenger side and work their way back from there. Happy hunting.

smartin · #6 01-28-2003, 01:49 AM

Aaron AND LRG - Thanks for the reply. The fluid is hydraulic, because I put 1 (blue) container of it into the green reservoir, started the engine and it immediately dumped it out onto the ground, the puddle being LARGE enough - volume of the blue container of the MB fluid. Nothing else is leaking THAT MUCH. I was in the back of the car looking at the valve that controls the level, when this happened. It was only when I went to the front of the car when I saw it dripping in the major way - clear in "color" on the black top driveway. And the reservoir level was at the bottom. I'm hoping (of course that this leak is at some sort of junction or connection in these metal lines - if not, can the lines be spliced or patched in some way? Or is this just wishful thinking? Once this leak is fixed, how can the system be flushed out? Thanks again.

lrg · #7 01-28-2003, 12:26 PM

Given the pressure, a patch on the lines is likely not to last very long. It may be possible to remove a section and with the proper tools attach the appropriate fittings to replace just the leaking section. All said and done though it'll probably be easier just to replace the whole section. To bleed the system put the rear wheels securely on blocks or ramps. Block the front tires, set the brakes and start the engine. There is a bleed nipple in the level control at the rear that you can open to drain the system. At idle the fluid will drain out relatively slowly. Be sure not to let the pump run dry; you will need to add clean fluid as the old fluid runs out. You may also want to drain the lines from the accumulators by disconnecting them. The system should self bleed just by running it so check the resevoir level a few times after you drive the car.

smartin · #8 01-29-2003, 11:30 AM

Well, the leak is somewhere in the return line where it runs under the engine - along the frame (crossover under engine) I know this because the lines are clean, the supply line to the rear valve crosses in front of the engine up away from the area where the leak occurs. The only line under the engine is the return line. Anyone have this happen to them? Is this type of line something that can be fabricated or something that the dealer sells? Anybody know what this might cost? 1985 300TDT (CA wagon). Thanks to any help - in advance. Along that same note - are the AC hoses something that can be fabricated or is it just better to get a new hose?

lrg · #9 01-29-2003, 12:54 PM

Sorry, I don't know about the hydraulic line. The dealer or better still a wrecking yard should be able to supply one. I very much doubt there is any difference between the CA and 49 state cars. The dealer should be able to verify that. As to the A/C hoses, a good auto A/C shop can make new ones using your old hose ends. Before you do that, I'd price new ones because they should be pretty readily available and might even be cheaper.

smartin · #10 01-30-2003, 11:14 AM

Thanks all. I am very anxious to get this suspension in good working order! I hear so many good things about them. I realize that it will take $$ and time and questions and answers. This forum is excellent. Thanks again.

smartin · #11 02-01-2003, 01:43 AM

The return line to reservoir goes under engine from passenger side up to reservoir. It looks as though trying to get this out as well as back (with new line) would be very difficult. Anyone do this before? Also, would it be possible to use a "hose" (flexible) such as onbe used for brake lines? I know of a hydraulic specialist comapny here that can make bent tubing type line, A/C lines, and hose type flexible lines - is there anything WRONG with this idea? With the flexible hose I could get it in, maybe anywhere I wanted to - probably keep it low and away from electricals. Any ideas? Thanks.

smartin · #12 02-05-2003, 01:56 AM

Anyway, this line seems to be under the engine - sitting on "saddle" shaped frame just forward of oil pan (between engine and saddle) I'm not sure (yet, as I have not yet tried to remove this line) but it seems that it may be difficult to just remove without having to move other things out of the way - perhaps raise engine a bit - Has anyone encountered this yet. Thanks.

smartin · #13 02-12-2003, 01:32 AM

LRG - Well the leak is definitely from the return line (to reservoir) leaks at line at a point under the engine. I know that it is the return line because this is the only line that crosses under the engine, the "pressure" line routs in front over the radiator (insulated with black rubber) around down passenger front fender under car - not under engine. So my question is if all the fluid leaks out from return line, did it leak out BEFORE the system could equalize (or something along that line) and therefore did not allow the system to pressurize, OR does this mean that the valve is not holding pressure somehow and is merely allowing fluid through valve body only to leak out under engine? Help.

lrg · #14 02-12-2003, 01:02 PM

Hard to tell. Normally the system pressurizes to the valve but if the valve is leaking even a little you'll loose all your oil. Also if your springs are a bit tired the valve my be in the open position more often than not. My guess is that probably the valve is OK but is bleeding off some of the pressure to the return line. Worst case you'll eventually need to rebuild the valve but from what I understand that's a pretty straight forward and not horribly expensive job. At idle the pump puts out a steady flow but not high pressure (at least not at the rear valve bleed screw). My guess is that if you patch/repair the return line the rest of the system will be OK. You may be able to cut out the leaking section where you have room to add fittings and patch with a braded brake line. A good brake shop should easily be able to handle it. Just be sure to tell them NOT to add brake fluid, they might not know any better.

luvmy84300sd · #15 02-12-2003, 03:53 PM

Hey Guys,
I owned two of the Lincoln Mark VIIs that had this auto leveling suspension and both were trouble spots. Seemed like I was replacing the "bags" at the wheels constantly to prevent that ground hugging look. Do the Benz versions of these systems last for a while? Also, what models can I expect to see these on (I know the SL's don't have them)? I'd like to acquire an SDL or 560 SEL and am worried they may have them.
Thanks!