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1988 BMW M5, 1989 BMW M3, 1979 Mercedes 450 SEL 6.9, 2006 SL55 AMG w/ P30 Performance Pack
I pulled the front block out today and found some interesting issues! One locking valve had a piece of PTFE ring stuck in a hole! The other one seemed to be stuck in the open position? Non of the rings on both locking valves were compromised. You may notice one doesn't have a white ring because I destroyed it 2 years ago when I was trying to seat the valve back in the block during the rebuild. (I had to re-used an old rubber ring). So it seems all the broken up PTFE pieces came both control valves! I didn't know they can migrate into the locking valves.
The one broken rubber ring seems to have split and I don't think there is a broken piece that is now floating around somewhere. I haven't clean out the block to see if there are any pieces stuck in there. I was initially happy thinking this was the cause of my problem. However applying 12 volts to BOTH locking valves did not activate them. Both control valves work fine. Assuming both locking valves were bad before I pulled them to test, would have there been more serious issues besides the left shock raising all the way up? Again, I was able to do full calibrations sessions and two rodeos when troubleshooting before I pulled the block today.
Ordered a used tested valve block and should have it by the weekend. The locking valve on the right seem to be stuck in open position? The locking valve on the right seem to be stuck in open position?
1988 BMW M5, 1989 BMW M3, 1979 Mercedes 450 SEL 6.9, 2006 SL55 AMG w/ P30 Performance Pack
Stop the presses! I figured out why both my locking valves were not actuating during my testing. I was not applying pressure to the spring when I fed 12v to them - just like in the video. I know the author of the video implied this but, my mind didn't catch it last night.
So if anyone is trying to test their locking valves - make sure you apply pressure on the spring just like in the video. The control valves don't need you to apply any pressure on them to activate w/ 12v being introduced.
Video:
Thanks for the update. It was a mystery why the valve block was mostly working but the solenoids failed your +12V test.
When I preventatively rebuilt my ABC, I installed a rebuilt valve block even though the current one was working perfectly. The rebuilt one also worked perfectly. UNTIL a month ago where one wheel sags after a week of storage.
Therefore, I now plan to rebuild first the original valve block and install that to replace the commercially "rebuilt" one.
Like many commercially rebuilt parts, they are rebuilt quickly to make money, not with maximum care.
Therefore, I suspect your own rebuild may last longer than buying a rebuilt unit.
In case anyone is interested, this is the ABC Valve body rebuild kit I purchased from ebay: https://www.ebay.com/itm/195077209380
Not the cheapest and not the most expensive. I liked that it had a very detailed description indicating that the seller actually makes the kit and doesn't just resell it.
1988 BMW M5, 1989 BMW M3, 1979 Mercedes 450 SEL 6.9, 2006 SL55 AMG w/ P30 Performance Pack
Originally Posted by mrvedit
Thanks for the update. It was a mystery why the valve block was mostly working but the solenoids failed your +12V test.
When I preventatively rebuilt my ABC, I installed a rebuilt valve block even though the current one was working perfectly. The rebuilt one also worked perfectly. UNTIL a month ago where one wheel sags after a week of storage.
Therefore, I now plan to rebuild first the original valve block and install that to replace the commercially "rebuilt" one.
Like many commercially rebuilt parts, they are rebuilt quickly to make money, not with maximum care.
Therefore, I suspect your own rebuild may last longer than buying a rebuilt unit.
In case anyone is interested, this is the ABC Valve body rebuild kit I purchased from ebay: https://www.ebay.com/itm/195077209380
Not the cheapest and not the most expensive. I liked that it had a very detailed description indicating that the seller actually makes the kit and doesn't just resell it.
I was able to activate the locking solenoids on my 4th try by putting pressure with my finger on the spring! The valve needs physical resistance to actuate with 12 v introduced in case you missed that in my post.
I too was hesitant to buy a remanufactured block because I know all they do is test them and replace o-ring. I don't think the valves are rebuildable from my research. The rebuild kits with the split PTFE rings are annoying and stressful to install. They tend to bind when you slide the valve in and get pinched. There is no way to verify they didn't get pinched unless you pop the valve out again. I pulled one back out to check and sure enough one broke and another was deformed. I had to use non-damaged old ones to finish. I lubed the crap out of the block, valve and rings and tried it again carefully. Apparently the locking valves can be rotated 360 degrees to verify they are seated correctly with no pinched rings. I was able to test that. However, the larger control valves won't rotate 360 and you just have to pray no rings got pinched.
I'll see if everything is back to normal now. I'm still thinking the worse that my plunger sensor which is internal in the shock is bad. That can't be replaced - new shock time. This is another worry of mine since my car is a P30 and the shocks and spring are different (part #) and I have no idea if Arnott would rebuild mine using the OEM firmer springs and whatever the P30 Sachs shock have different. A good coil over system with beefy sway bar kits are top of mind for the next few years.
Last edited by m5zealot; Aug 28, 2025 at 12:42 PM.
Reason: spell check
Just sold my '11 Porsche TurboS cab for an '03 SL55!
As far as I can determine, nobody has set up a hydraulic test rig to test these valves. Many say "tested" but that's bull. Although, if a salvage yard wanted to, and the car was not destroyed, it could cycle these valves before removing them and also let the car sit for a few days to watch for the droop that results from very slow (usually) leaks through the blocking valves. I talked to several of the "rebuilders/testers" and none had a good answer about testing. And yes, "rebuild" seems to stand for new seals. I struggled with this droop and even bought a new OE block.......that leaked. Finally solved it with a cheap (?$100) used block off of ebay. BTW, MB warrants their parts, but to get them to do that you have to take your car in so they can evaluate it. I'm so far from a dealer that I never made it. (out about $1500 !! ugg).
1988 BMW M5, 1989 BMW M3, 1979 Mercedes 450 SEL 6.9, 2006 SL55 AMG w/ P30 Performance Pack
Sorry I forgot to post a follow up. All is well with the left front shock now. Replacing and broken rings fixed the problem! Hope this helps someone in the future.
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