danmm7

This is a weird one...

Last week, i rebuilt both ABC valve blocks - front and rear. I also replaced the pressure accumulators on the front and rear, just in case.
Since i did not have a new one handy, i was not able to replace the second, smaller, return line pressure accumulator.
I put everything together, flushed the system, and everything worked great. Drove the car for 50-60 miles and the ABC worked as it should. No issues. I was very happy with the results.

*******
Today i received the brand new, smaller, return accumulator and i decided to pull the rear valve block out to replace it. Why did i bother, i am wondering now.

I disconnected only 3 of the 4 quick connect pressure hoses since the last one appeared stuck.
I did NOT disconnect any of the wired connectors from the solenoids, so no wiring was touched, moved or changed. I swapped the small pressure accumulator without fully removing the valve block from the car, and put everything back together.

Started the car and it can raise it up and down. No error codes. I did a manual "up-down" procedure about 20 times. All 4 corners go up and down just fine. Fluid level is good.

>>> Here is the problem: As soon as i turn off the engine, the rear left corner goes up on its own to max height. It feels like, as soon as the car is off, something pumps it up to the max. As soon as I start the car, it slowly lowers itself to *almost* same level as all the other 3 corners.
I measured the height at all 4 corners with the car running, and i discovered that the rear left was always a bit higher than the other 3 corners. That was not the case before.
I hooked up my iCarsoft scanner (did not have time to plug in the Star scanner tonight).... and the Carsoft scanner confirmed the same - the rear left corner always sits a bit higher than the other 3 corners.....it raises and lowers itself when i play with the ABC mode button, but it's always a bit higher than the other 3 corners. As if it's not calibrated.

And of course.....as soon as i turn the engine off.....that same corner shoots up high.

Some observations....

1. There are no warning lights or messages or error codes related to ABC or anything else. No visible leaks either.
2. Only one corner shoots up with the engine off.
3. I did NOT do a flush this time.... just manually raised the car up and down, about 20 times
4. Not sure if this is normal... but i hear slight "air"/pressure being released when the car lowers. Not sure if it was doing that before or this is a new thing.
5. I wonder if i have air trapped in the rear left strut and if this is even possible. I did not open any of the bleed screws, but i did not do it last week either, and i had no issues.
6. Can a defective ride height sensor be causing all this? If yes, why would it just fail today, while i was replacing the small pressure accumulator? Makes no sense.


Any ideas what could be causing this weird behavior?

I am open to any suggestions. I have a Star tool, so i wonder if a Rodeo procedure may help?!
Perhaps when i was disconnecting some of the valve block lines today, i introduced some contamination and now the valve(s) are clogged?!?! .... but if that's the case, why the suspension works fine when the engine if ON.... and then only one corner shoots up when the engine is turned off? .... and why is this same corner a little bit higher than the others when the engine if ON??


Thanks!

bobterry99

I don't think it is possible to know why one corner is a bit higher than the other three, but I would remedy it with a Star Diagnosis level calibration.

It's my guess that both control control valves for the left-rear strut are contaminated and unable to seal-off the strut completely from the pressure supply. When the engine is running, the controller corrects for this through valve action, but with the engine off it no longer does. CORRECTION: According to the WIS the controller will release oil from the struts as necessary to maintain correct level for up to one minute after engine shutoff. I think that makes the test described immediately below essential.

A test of the above theory would be to shutoff the engine and quickly remove the negative cable from the trunk battery. If the car still rises as before, you know that it is purely through a mechanical anomaly and not an electrical one.

If the control valves are contaminated, then two 15-minute Rodeo routines run back-to-back may cure the problem. As you surely know iCarsoft can not do this -- SDS can -- and this is among the many reasons why I advise members not to purchase iCarsoft.

danmm7

Well .... let's just say that the STAR software I bought is worth every dollar I spent on it.

I have not fixed the issue yet, but after a series of tests using Star, I was able to narrow down where the issue is.
I took some pictures of the computer screen so you can get an idea. See below....

First, I measured the height levels at each corner using the sensor readings and the rear left was way off, not surprisingly. It just sits higher than all other corners, even if the engine is running.
See picture:




There is an auto-calibration procedure in Star that i was able to run, it lowered that rear corner a bit more, but it still ended being higher than the others. See picture:



After the auto-calibration, the values did NOT stick. As soon as I turned the engine off, the rear left bounced up again.

I checked some of the sensors' parameters. The plunger sensor reading was interesting, not sure if there is anything alarming though:



I performed 2 separate rodeos and unfortunately, it did NOT help at all. I also opened the bleeders on each of the rear shocks, fluid, and some air came out, but the main problem remained.

>>> During the rodeo test, i noticed that the other 3 corners were lowering a lot more than the problematic left rear corner. It was always the highest point of the car. It's like something keeps that rear left strut constantly filled and lifted...even during rodeo test.

>>>> There is also a Star test that allows you to manually raise and lower each corner. As soon as I attempted to do this for the rear left, I heard a click and the corner quickly popped up to the highest setting. Trying to use the "lower down" button on the screen for the same corner, just produced a click from the valve block (i can clearly hear it).... but the car did not move down at all. So I can tell there is an electrical connection and the valve is triggered when needed, but nothing happens.

So finally, i started to run some diagnostic tests for the ABC hydraulics and one of them suggested that I should do a "dynamic test" for the whole system. It's kind of similar to RODEO but shorter.
This is where I finally got a more specific diagnosis. See picture below:



As expected, there is an issue with one of the control valves. Per the picture above, " Y36/2 2y1 , strut control valve sticks. "

Now the question is .... what does this really mean? Is the valve just dirty OR is it defective/dead?
Keep in mind, i rebuilt all the valves last week with brand new seals and they all worked great until I decided to disassemble the rear valve block yesterday to replace the small pressure accumulator.

How did the valve get stuck because of that?!?! I did not touch any of the valves. The seals are brand new. The fluid is clean. ...yet, it somehow "Sticks" and my rear corner pops up with engine off.

Also....which valve exactly is Y36/2 2y1 when I am looking at the valve block? If i decide to replace with a "new" one, i don't want to replace the wrong one.


If it turns out, it's not the control valve ... per the picture above, I must have a bad strut.
All 4 struts were replaced 30k miles ago with Arnott units. They are not that old for sure. And they were all working great 2 days ago.

bobterry99

I suppose you did not do the experiment I suggested which involved disconnecting the battery. In this case the valve would be "dead" electrically, and my expectation is that you would still have the problem with the left-rear corner rising. The ineluctable conclusion would be that you have a valve block with two valves incompletely closed presumably due to some particle contamination which entered the system when you replaced the return line accumulator.

It is one of the two larger valves. But the associated "locking" valve is also not functioning properly.

With the car off both the control and locking valves should be closed. Since the car rises, neither valve associated with the left-rear corner is completely closed.

danmm7

bobterry99, yes, you are correct. I did not disconnect the battery at all, due to some other concerns, unrelated to this issue.
I can tell you that the rear left corner jumps up as soon as i turn the key in the ignition and the engine stops. It takes less than 1 sec for this to happen. I assume, as soon as power to the valve block is interrupted, the corner jumps up.

However, I did rodeos and a full set of STAR tests and simulation and you see the final verdict from STAR. You saw the screenshots.

I hear what you're saying about both valves being stuck/dirty/compromised and not closing.... and i do agree with your logic.
What bothers me is....how the hell did both get contaminated at the same time and both got "sticky"?!?! I mean.... i just rebuilt these valves few days before that with new o-rings and all, and they were all working great.
I guess, disconnecting the 3 hydraulic lines during the accumulator replacement caused massive "damage" inside but have no idea how it happened. This is beyond puzzling.

I ordered a new set of o-rings, just in case, and once i receive them.... i will disassemble and clean everything again. I don't want to do it before the rings arrive because i may discover that somehow i have bad o-ring(s) and i will be stuck with a disassembled valve block for few days. Plus i hate dealing with the quick connect hoses. I want to save myself an extra interaction with them, if possible.

knowbenz

When you pull it apart you can apply 12v to the solenoid to activate it. Make sure it is in the middle position and not stuck at the end position allowing pressure to bleed into locking valve

danmm7

I just disassembled the valve block..... and looking at one of the solenoids, that tip at the end that goes in, middle out and fully out .... it is currently fully IN.
On the other solenoid, it looks like the tip is in the "middle out" position.

See picture:



The solenoid is now perfectly clean. I see no debris or anything impacting it's function. When i first took it out of the valve block, i did see a small, thin, metal/aluminum piece of metal 'shaving' on the side of it.

Should i apply 12V to it to see if it will go back to the middle position?

What if it doesn't and keeps going to the fully IN position? Is this fixable or i have a bad solenoid?

Thank you!

bobterry99

I have never disassembled a valve, but I am quite certain there should exist a spring or two which return the valve "spool" to its center position. So, you shouldn't need to apply 12 volts DC.

danmm7

I applied 12V.... the solenoid moves/cycles the center rod in and out.... but when power is removed, it goes back into the full IN position. As a result, i see how the center set of round holes is partially open because the piston inside does not seal them (when power is off). This likely explains why my car jumps up in one corner when the engine is turned off.

The other solenoid also moves, but when power is removed... it stays in the middle position. The middle set of holes is sealed by the piston inside.

Not sure if this type of solenoid can be disassembled. The small valves do have an external spring.
The larger ones.... all springs must be internal to them, but i am not sure how to disassemble.
I am also not sure what caused it to get 'stuck' in full IN position. It can't be dirt, because the valve is very clean now and it still stays in the full IN position. Feels like a return spring is missing or maybe broken inside.


Unless someone has any ideas on how to fix this..... My only option is to install a spare used valve that i purchased in the past.


Thanks!

bobterry99

I agree.

knowbenz

If it is springing all the way back in then you likely have a broken internal spring. Replace the solenoid, there isn't really any way to open it and reliably put it back together. This is a solenoid I made a cut away example of, you can see the two springs that keep the valve in the center with no power applied. Reversing the polarity will move it the opposite direction.

Now that I think about it, if you look at the second picture you will see how the valve portion threads onto the rod with the springs. Perhaps there is a chance it has come unscrewed but I would suspect free movement of the valve to an extent and it probably wouldn't spring back quickly if that were the case. I have that valve here taken apart if you want any close ups of anything

danmm7

And here is an update.... still not good.

I replaced the control (big) valve with another one, from a used valve block. Before i installed it, i replaced all the rubber seals.

I put everything together, filled with extra fluid..... cycled the system 10-15 times.... car goes up and down fine, no issues..... except, as soon as i turned off the engine, the same - rear left corner raises up SLOWLY.
With the old valve, it was jumping up right away. Now it is slowly and gradually going up for up to 10 seconds after i turn off the engine.
As soon as i start the car, put it in gear and move it, the rear corner lowers itself automatically.

Ideas?!?!

Just to be safe, i decided to also replace the block (small) valve on the same side. I swapped with with a freshly rebuilt valve from another valve block.
This made no difference, unfortunately. Clearly the issue is not in the block valve!

I hooked up the car to STAR and did a short rodeo, plus the 'dynamic test'. It did not give me any errors this time, but i also noticed, just like before, during the rodeo, this left rear corner never lowers itself as much as the other 3 corners.

During the dynamic test (it's like a short rodeo), the rear left corner did go down, just like the others. No errors/faults with the system were reported.

I also did an individual test for that same RL corner. There is a STAR option where you can manually turn on/off the block valve and then lower (-) or raise (+) with the control valve. Well.... for the rear left corner.... as soon as i energize (on) the block valve, the car goes up. The issue is, I cannot lower it with the control valve at all. Clearly there is a problem with this control valve. It's like the control valve does not respond or receive the up/down commands from STAR. I don't even hear a click now.

On the right side (RR) corner, as soon as i energize the block valve....car goes up, but i can easily lower it and raise it with the control valve all day long.

Any ideas?!?
I am staring to run out of options. The only thing i can do... since i have one more spare control valve, i may swap it again and see if it makes any difference. How can have TWO bad control valves??

Just to summarize....so far:

• The front and rear ABC blocks were fully rebuilt with new seals and new pressure accumulators 2 weeks ago. Everything worked for few days, no issues at all.
• I decided to replace the rear small pressure accumulator (this is when my hell started) so i disconnected the pressure hoses and replaced it. Easy.
• After this little procedure, car started to jump up in the rear left corner as soon as engine was off. Rodeo made no difference. STAR said - "rear left control valve sticking".
• Manual test confirmed that the control valve does not sear properly - likely broken spring inside.
• Rear control valve was replaced with a rebuilt used valve from another car. This made SOME difference - now car raises up slowly in RL corner after engine is off. Does not jump, but still not normal.
• Replaced RL Block valve with a rebuilt one - made no difference. Car still slowly raises up when engine is turned off.
• What's next?!?

danmm7

Last update....

All fixed and working well now. Finally!!

Replacing the control valve, with a second spare, did the trick!

I am having really hard time comprehending how all this is even possible: for the first (original) valve to just fail where it was visibly leaking due to bad internal spring...
then the second valve that i took from another Benz valve body, i rebuilt it with new o-rings, tested with 12V, it visually "looked good" .... installed it and it had similar issue as the original, but not as bad.
And finally, the third valve, from the same used valve body.... i only cleaned it well, visually inspected the o-rings but i did NOT replace any of them - i installed it and car is happy now!

2 bad control valves?! really?

Honestly, the only common thing between the two bad valves was that i replaced the o-rings on both. One may assume that the o-rings were bad, wrong size, etc..... but if that was the case, why the other 3 control valves i rebuilt with the same set of o-rings, never had an issue?? Same rings, from the same source were used for all 4 corners.

If anyone tells you these ABC solenoids don't fail much - send them over to me.

knowbenz

I've had blocks with two bad valves and many valves go bad individually. It isn't that uncommon. The same way debris gets caught up in locking valves it gets caught up in control valves. I've even had the main part of the solenoids separate from the portion that goes into the block.

danmm7

That makes me feel slightly better. I guess i am not the only one who had to deal with not one, but two bad control valves at the same time.

The first one definitely looked like a spring inside went bad/broke (not sure how and why?, it was out of nowhere).
The second one, likely had a small internal leak due to weak spring, or who knows what else ... but since it came off another car i had no history off,... it may have been leaking for some time before. I assumed it's good, installed it, and i was wrong.

Given my experience, it almost sounds like it's good to always keep a couple of spare control valves around. ... just in case. I mean, if these failures are common after all, how can one be sure that another one of those valves won't fail tomorrow? Most of our cars are pretty old, with good amount of miles on them by now. I expect to see more and more valve failures in the future.

And the dealer does not even sell these valves individually. Not sure if we can get them NEW anywhere.

knowbenz

The individual valves aren't available new. Every now and then there are some listed as new from china but they look like rebuilt ones based on some of the pictures. I keep good used, rebuilt ones in stock for this very reason