bha

I'm having some weird issues where every day at some point the "Malfunction" light with an up arrow comes on. It is a suspension malfunction light. I diagnosed the codes and got 5285 which means it is taking too long for the compressor to pump up the system and it times out. When there is an issue, the front struts are a bit low.

Compressor is 2yrs old and was genuine OEM. Works perfectly (ran all compressor tests in DAS)

Here's the weird part:
1. I replaced both front struts (Arnott) and one rear one (used MB). They weren't leaking, they had mechanical problems (ball joints clucnking etc) so I replaced them myself.
2. No problems at all after that for a week.
3. Replaced valve block because right rear strut kept leaking down overnight. This fixed the issue
4. The "Malfunction" indicator issue started. I also get STOP car too low about once a week too (and the front end REALLY drops and scrapes everything). Usually restarting the engine makes that go away and the suspension raises back to normal, but the Malfunction comes back after a while as usual

I have no idea how the valve block could have caused it. Thought I got a bad one, so I replaced it with another one and am still having the problem. I'm pretty sure it is something related to the valve block, because had no problems at all (even after the strut install!) until I touched it.

Valve block is properly installed, all nuts torqued properly, I clipped off a tiny amount of each pressure line so the sealing area inside the nuts is new, etc.

I guess I could do a leak test but don't see why it would leak.

My two guesses are:
Since the problem is in BOTH front struts it can't be a strut pressure line. I'll re torque the nuts on the tops of the struts because I'm not sure I did that the first time and maybe there is a leak. But don't see why one would leak and cause both to be an issue as they are separate pressure lines of air going back to the valve block.
Maybe I nicked the wiring harness while doing the valve block job and it is intermittent? I know there is an area where they fray and ground out, but that blows the fuse and obvioiusly mine still works.

I ran the pressure tests a while ago in DAS (Compressor to valve block, valve block to strut, etc, etc) but maybe I'll do it again and see if any issues come up.

This seems isolated to the compressor and pressure line between compressor and valve block (at first guess) since it seems to not affect any one strut. But then why are both fronts low together? That would mean the problem is two pressure lines, cannot be the compressor, etc. Doesn't seem possible.

Again the problem started when replacing valve block, but that doesn't seem to be the issue. I was curing a problem that only had a minor leakdown (rear strut drops after about 24h) so it's not like there is all kinds of new pressure in the system now that a 'major' leak has been fixed and is causing somewhere else to blow out.

I might actually put the original OEM one back in and see if the problem goes away. Waste of time and it will start sinking in the rear, but that will tell me if it's the block for sure. If that's it I guess I'll have to spring for an original MB one from a dealer (very expensive!) even though I've already bought two different aftermarket ones.

dlafever

So, having replaced my fronts about a year ago ... are you sure the ride height potentiometers are working/connected correctly? it is possible to miss this or have a binding linkage that can lead to some odd readings. I think you're on track with re-testing the system via DAS ... run through the whole test suite and I bet your find your issue. When i replaced mine I used the Bilstein aftermarket parts because they are only $100 more online than the other aftermarket suppliers and WAY less than the dealer parts.

bha

I assume the ride height sensors are fine, since I didn't touch them at all. Would be weird for them to stop working the day I touched the valve block. I would also think that since there are two, the car would be higher on one side than the other (I am getting high vs. low equally on both sides..They both move down together when there is a problem)

Thanks for your help, I think I'm going to run every single test in DAS again and see if I can find a leak. I don't think it's a huge leak as the car operates normally most of the time (the STOP car too low only happens once a week). Once the Malfunction error pops up the car times out and won't reset until you restart the engine. So it definitely seems that the compressor is running for too much time (not sure why)

I'll also look at the compressor wiring in case it is flaky (maybe the system can't run the compressor and that's why it is timing out? Although the error seems to be that the compressor runs but won't build up enough pressure in the allotted time)

dlafever

Sounds like a plan. I mentioned the ride height sensors because I replaced the lower control arms when I did mine and remembered having to disconnect/reconnect them.

Good luck!

bha

Ah, I see. Thanks for mentioning them.

My car is a 4matic so no control arms needed to be touched during the install. 4matic actually just has one nut on a ball joint at the bottom, plus the 3 nuts at the top. That's it and the strut comes out.

bha

Hmm.. drove 80km today (approximately 50 miles).. first half of the drive was at 140km/h (85mph) and second half was at slow stop & go traffic speeds.

Not even the malfunction light came on. Usually I can't go more than about 5 mins before it comes on. And today.. nothing at all

Haven't touched the car since I drove home last night (when it did come on).. I parked it in the garage and then came out and started it up this morning. Didn't touch a thing other than that.

Maybe it fixed itself? Will run diagnostics this weekend to see if any errors.

dlafever

HA! Daimler secretly inventing the self-healing car, years ahead of the competition.