Air suspension leak

[sweeper]

Ok, so i have had a small air leak for a while now, in fact it was reported by previous owner and checked during a service but no leak was found, so the leak has got a bit bigger so the car drops noticeably over night on the left hand front, I checked the strut for leaks and during that process the hose actually blew off the strut just as i was removing the plate that covers it on the R Class, I must have just knocked it a little, I quickly pushed it home again and it will need looking at (new pipe and fitting) once I have located the leak, as the leak is very small I decided to isolate the strut using a ball valve, just cut the pipe and used a push fit ball valve, run engine and allow suspension to level off and turn the tap off, left overnight and the car was still level.
So the leak is either in the line or leaking back through the valve block, so I bought a new fitting for the valve block and got some 4mm hose (I checked the valve block connection for leaks first, none found) so close off the tap (no need to support the car) and took the pipe off valve end (quite easy to get to on the R, just behind headlamp and no need to remove bumper or wheel arch inners) and put a temporary hose form valve block to ball valve, turn the valve open and left car overnight and it is still sitting level (up during the day due to high temp and down a little when cooler but same both sides) so the leak id somewhere in the line, so i'll put a new line through and drag the old one out just to see where it is leaking. Interestingly my local Mercedes dealer reckons most of the leaks are the lines and not the bags or valve blocks.

 

[Oonnzo]

I wouldn’t be so quick to pinpoint it to the lines. I’m onto my 3rd set of front bags and each time I have intermittent sagging, it sometimes stays up for days at a time.

The bags develop fine pinholes that may or may not seal when parked but they eventually get worse enough to drop consistently.

I just changed over a bag from aliexpress on the weekend (I’ve had the strut in for a while but first time I’m using one of their bags).

At $700aud for an arnott bag (only) or $250 for aliexpress bag and strut - I thought I’d give it a try and all seems good so far.

 

[sweeper]

It had to be in the line, proof was in the temporary line curing the issue and the bag was isolated by the ball valve as a way of shutting it off over night, also confirmed now I have removed the line and fitted a complete new one, ( I bought fittings from Mercedes at £3 each and some nylon tube off ebay, make sure it has 20bar working pressure) inspecting the old line I found two areas where the pipe had been chaffed almost right through and this is where is was leaking slightly, this has been leaking for some time as a previous owner had the fault investigated (clearly not very well as they couldn't find a leak) the area the pipe was damaged was where the hose goes around the r/h headlamp then down before turning back up to the valve block. Left any longer and one big bump would have burst the hose leaving the car undriveable.
I have had a Jaguar with air all round, it was 16yrs old when i sold it, it had never had and new air suspension parts, not a line. bag or compressor and it was poor workmanship/design that led to the line failure on the Merc., there is no protection on the lines and they were poorly routed which didn't avoid contact scrub points. My advice at the first sign of any leak would be to fit a ball valve near the strut/bag to rule this out, you say you are on your third set, it is unlikely it is in the airbags, why are they failing so quickly? Maybe the heat? but bear in mind mine in the uk we have big changes in weather and road salt to contend with, it can be -10c or above 30c and we have some rough roads.

 

[Oonnzo]

That’s great to know where to look if I suspect the lines are failing.

My experience with the bags seem to be common based on forum posts. It sounds like you’ve been lucky!

 

[mioba]

Good isolation and ID of the the failing part.
Sometimes these pinhole leaks are a real pain to find and "some" garages dont like the job because its a head scratcher and time consuming. This leads to a labour (time) extensive job which annoys some customers as they a see a bill for hunderds for the want a very cheap part.

 

[sweeper]

photo of damaged pipe

 

[sweeper]

That’s great to know where to look if I suspect the lines are failing.

My experience with the bags seem to be common based on forum posts. It sounds like you’ve been lucky!

My Viano is on the original bags, lines and compressor, 330000 miles! the compressor mounts have collapsed but its still working