Spectacular Air Spring Failure

[S2central.net]

Missus gets the wagon home tonight after calling me to say she was nursing it home slowly after the suspension light came on - it was dropping the front, raising it, then dropping the back and going a bit bonkers.

She gets into the driveway and I was taking pics in amazement of how high the front was. After the 3rd pic the front left air-spring failed in explosive fashion. All the neighbours started twitching curtains and opening doors to see who had been shot dead on the street.

I have never heard of an air-spring failing like that... I also have no clue how it got so over-pressurised... mental - there are parts of air-spring and god knows what else lying on the driveway. Thankfully nobody was standing close to that side.

Guess I am looking at 2 x 200 quid for new air-springs - where is that case of beer ?

[spink]

Arnott ones are cheaper than that from memory (been a few years though) ,I found they sit a bit higher after fitting but you can adjust height of all 4 corners on vcds

[S2central.net]

Arnott fronts are £300 each on a quick market scan tonight - happy to hear if anyone knows a good source of them for sensible money. There are loads of vendors for £100 specials from the far east no doubt the quality will by shyte.

[S2central.net]

Friday,03,June,2016,22:51:15:36838
VCDS Version: Release 10.6.3

Address 34: Level Control Labels: 4Z7-907-553.lbl
Control Module Part Number: 4Z7 907 553 G
Component and/or Version: - 2C1A1 D052
Software Coding: 25500
Work Shop Code: WSC 00899
VCID: 499241A0593F
4 Faults Found:

01769 - Sensor for Vehicle Leveling; Front Right (G289)
27-10 - Implausible Signal - Intermittent
01780 - Sensor for Vehicle Leveling
04-10 - Mechanical Malfunction - Intermittent
01577 - Turn-Off due to Over-Temp
35-10 - - - Intermittent
01575 - Control Switched Off
35-00 - -

[S2central.net]

Ordered a pair from a reputable looking seller on eBay - £170 each including new top mounts, bolts & seals and that includes shipping. They have 2yrs warranty - which is 2yrs more than you get on the cheap-skate-specials. I will need to check the state of the front right height sensor as well - it might be unrelated, but its another £120 odd if that needs replaced. Total pain in the ***, but to be fair - could have been lots worse if it happened while driving and/or bits of shrapnel hit somebody. The only damage is a ringing noise in my ear and a slightly singed PayPal account !

[Henkjan]

isn't there supposed to be some form of mechanical overpressure protection? like a proper relief valve set well below the burst pressure of the suspension bits?

[S2central.net]

You would think so - I will check the manuals - if that valve exists you would think it's in the valve block down beside the compressor. From memory the only pressure sensor I can recall is in the reserve tank - rear left corner. You would think the height sensors at the front would be telling "enough" to the control unit but if one or more is flaky and says the corner is too low then maybe the controller keeps pumping air to that corner to give it more height. So you would think a failsafe mechanism based on mechanical pressure relief would be wise.

[johne]

From my experience of working on Range Rover Classic air suspension, the overall max system pressure is set by the air tank bow-off valve (150psi). The springs are mechanically constrained by the damper and can take being inflated to the full system pressure.

True, the RR air springs seat top and bottom like a car tyre whereas on the Audi the top is held with a steel band with only the bottom seating like a tyre, I believe.

I wonder if in your case there was already a cut in the air spring rubber or some other defect that let go when under max pressure.

Will be interesting to see where the failure started from when you take it off, usually it's in the part of the rubber fabric near the bottom that folds over itself.

John

[diesel des]

Yea sounds like a weak bladder let go when at Max Operating Pressure. There will some sorta relief or cutoff I'm sure to protect the parts from pressures much above MOP.

Your want to hear a 4 inch vent at full chat at 85 bar....

Sent from my LG-H955 using Tapatalk

[S2central.net]

The front had been showing signs of leaks recently - it was weird - if you parked it, locked it walked away it would rise to level 3 as per the norm but then leak away overnight at the front most nights... but if you put it on level four before shutting off then it would hold that all night and longer no probs.

Anyway - see attached pics...

2534 is evidence of how sky high the front was on Friday night - that pic is seconds before boom - if I had been on video mode, it would a YouTube sensation already (or not)

2540 is the 'mex-spec low-rider' look (herself's term - not mine) on Saturday morning after the boom... looks kind of cool way down there alright, but totally undriveable

2542 is the destroyed airspring on front left - hard to say where the weak spot was yet

2548 is the reason for the level control fault codes from front right... the lever had seized in the lower joint (where it connects to the chassis leg) and the stress had caused the upper joint to be torn out of the link rod.

My presumption is that the resulting signal from the front right sensor was that the car was too low (according to level controller) and it needed more air to lift the nose, but quite why the front sensor on the left side wasn't then checked is a mystery to me. Regardless of the front left spring maybe being weak - I still think its a control system failure for so much pressure to have been allowed to build up in the first place.

I checked the SSP manuals last night and there is no mention of any mechanical fail safe - yes there is overtime protection for the pump, but thats it.

There is a pressure sensor within the valve block which is used round-robin to measure pressure of each corner (and the reserve tank) - I wonder is that faulty and giving out low values to the level control unit. Have to investigate that when its up and running again.

I have to order a new level control sensor for the front right - guessing not much change from £150 for that from TPS.

I need to finish working on back of the beast first though - the rear brake unions that meet the flexi hoses just melted away at the sight of a spanner yesterday - oh joy.