MK19

I've got suspension sagging about an inch or two on both front and rear of the right side and am trying to determine if I need to reseal both of the valve blocks or will I get lucky and find out that one of the two valve blocks operates the right side.

Given that at least one is bad, I should probably go through both as further failure can't be too far behind but any opinions there would be appreciated too.

Thanks, MK19

MK19

I've researched further and found that the front and rear valve blocks operate the front and rear struts respectively as one might have guessed. So it looks like I'll have to go through both blocks.

latemodel21

This is a useful guide to R230 ABC
http://mercedes-abc-drive-carefully....y-part-of.html

On my own 2003SL55 (which I bought 9 years ago with 53k miles and now is has about 130K), I have found that sometimes one or more corners would sink over time (hours or days) and this cleared up in some cases on its own and in other cases, by flushing the fluid (I am assuming there was a chunk of debris on one or more valve seat). Eventually (40k miles ago?) I did take out the front valve block and replace the o-rings. AND, while I was in there, I stretched the small "shut off valve spring" on each valve assembly (to increase pre-load on part of the valving that holds the car up when it is shut off). Not saying this is a approved solution, just something I did and it seems to work (although, changing the o-rings may have made all of the improvement).

HTH,
Chris

MK19

Thanks Chris, yes......helpful.
MK

carguyshu

2 valves control whether fluid is going in or out and 2 valves are locking valves, which when they are activated doesn't let anything in or out. The locking valves are the taller ones and they only activate when the car is stopped. These are the ones that cause the sag over time issue. If you release the pressure off of each strut (there is a bleed valve like found on a brake caliper near each strut that does this) you can even pop off the valves swap the rings and pump them back on without having to remove the entire valve block assembly from the car, which is a bit time consuming.

MK19

Thanks CarGuyShu. That helps as I was assuming I'd have to pull the whole block.

MK19

Here's more on this saga among others on my learning curve;
Background: New Pump and reservoir w/in last year by others, and in the last month 4 new accumulators and new RF strut. I found no dark fluid found anywhere in the system....nice.
The only thing wrong with the system initially was likely the large rear accumulator (prompting the red ABC caution message over bumps) and minor weeping/torn boot at the RF strut. The LF strut was a new MB item installed before I bought it 2 months back. I used an Arnott unit on the RF.
After replacing these recent parts some limited usage I ran a rodeo then the automatic leveling w/DAS.
Then I noticed I had a sage of about 1 - 1.5 inches in the RR. The LF corresponding on the high side. Ok...…...must have popped a Shut Off Valve seal in the rear block. No problem as I have a background in aircraft hydraulics design and manufacture etc. This sagging would occur very quickly...….maybe 1-3 minutes max.
So I put new seals on the 4 vales in the rear block. BTW a few seals showed evidence of their working against pressure but they were really fine to my eye. No extrusion of the TFE backup rings and no nibbling of the orings. But I'm sure there were original to the car and the orings had set a bit.
At first it seemed fine, I blead and re-leveled it. But after about 70 miles, I drooped again in the RR! Now, even with the Hight setting on low (normal), when I turn the key off, the car immediately settles all around and the RR corner drops the same 1-1.5" or so.
Hmmmmm, seems to indicate the SO valve seat is bad, but it (both really) looked great. Hard to imaging that valve leaking that much all at once. I could see a slow leak over the valve seat, but not the 'dump' that is occurring.

Thinking of going back into that valve block but want to determine which of the two SOV's is associated with the RR (Blue or Yellow?) I can chase the hydraulic lines if I have too but that's no so easy in that area.

Other wise the system works fine, no codes either. Could it be the RR strut?? (fluid bypassing the damper piston seal??).

BTW for those contemplating the rear valve block reseal:
As suggested elsewhere here I found that I remove the 4 valves from the block w/out pulling the block and breaking all of those tube fitting (all a source of future leakage). By removing the clamp over the tube support block (rubber) just inboard of the valve block, and juicing up the rubber support there so the tubes could all move freely, I was able to pull the whole valve/bracket back and more or less flip it upside down, supporting the top of the bog accumulator on blocks inside of my drip pan. From you'll have to remove the brackets to get at the 4 valves. I had dreaded the job of getting the valves in/out of the block but the control valves have a non-critical surface covered by the protective rubber rings that allowed me room for a pry tool. The SOV's were even easier: Id' jacked both rear wheels to relive pressure but forgot to vent the system at the local bleed port. All I had to do was get the valves rotated to the removal positions and a bit of back/forth and the pressure just popped the out spraying an ounce or two of oil reach......….was a small price to pay. Chris...….thanks for your great pictures, I referred to them several times along the way, VERY Helpful.

More to follow.

latemodel21

From my understanding of the system, a leak inside the (RR) strut could only explain the drop if fluid was actually leaking out of the strut. It sounds like you have been very thorough, but I wonder if the rear block is 100% debris-free.

Chris

MK19

You were correct again latemodel Chris, I pulled the Red (right side) Shutoff Valve and was able to solve the problem.

I found nothing apparently wrong - all seals in place, no flaws or damage there. No apparent contamination or damage either on the valve poppet or valve seating surfaces and no contamination within the cavity in the valve block either. And I looked at all of it very carefully albeit without any magnification. So seeing nothing amiss, I did two things just hoping something would work. 1) With the with the valve poppet in place and against the valve seat I used moderate pressure on the poppet while rotating it against the seat. Much like we might have done years ago to lap engine valves, but I used no lapping compounds or anything besides the residual oil. then I did a crude leak test by squirting WD40 into the valves side ports while very lightly holding the poppet against the seat. It appeared to seal well. 2) I stretched the spring out by another mm or so to add to the ~0.5 mm I'd previously stretched it. These springs are tough to stretch, so this time I used two pairs of needle nosed pliers to grip though and across the end coils to get some force on it. Then I more or less straightened the ends so that the spring stood up straight on either end. And...…...there was immediate change in the leak down rate to near nil. Both sides drooped about 3/16" over night, partially or maybe entirely do to oil contraction as it cooled off.

Also: to my original question of which valve operates which strut? The Answer can be found in the attached and excellent paper...…..its the best overall functional description of the system, its parts and its issues that I've come across. Bottom line; Valve Block Port FB1 goes to the Left side and in line with that side of the valve block are the Yellow SOV and the Blue Control Valves. The FB2 port for the Right side corresponds with the Red and Green valves respectively.

Hope it helps the community here.

MK19

Follow Up: The right rear drooped again although it took 24 hours this time, so I had made progress.

So I pulled the Red SOV again and lapped the popped into the seat, more aggressively this time, and stretched the spring another 2 or 3 mm's and it seems to be holding well.

Side Note: It seems that the poppet is held against it's seat by the pressure trapped in the strut (and the pressure resulting from the weight of the car). This force is far greater than that of the spring so the stretch probably does very little. The purpose of the spring is to get the plug in the hole in the first place, then the trapped pressure does the rest.
Cheers, MK19