Hiya Gents
Ok got an issue now with the suspension ..
i have ordered a replacement AMK unit , ready to install tonight

But although the suspension system is tied into the Brains of the car , i believe most of this is via sensors all over the place .
In theory the actual suspension system should be quite simple
Air is sucked into the pump via the filter then distributed to 4 airbags which the Height is managed by a level sensor at each strut ..

My question is ,,, what other issue's can occur other than Pump Failing, blocked filter , leaking airbag , faulty level sensor

" Read somewhere about powder in the system " what is that ?

i know i am looking at this simplistically , But that is how i start my diagnosis.

cheers for any guidance in advance

keith

There are three valve blocks that distribute air and control the level in each corner bag. One is adjacent the compressor and sends air to/from the reservoir and to the front/rear valve blocks. There are two axle blocks, one at the front, one at the rear. The front one is fixed to the rear of the front bumper on the right corner, the rear one is on the left rear suspension strut - you can see it through the wheel arch.

The valve blocks are connected to the centre valve block by pipes and then are connected to each air bag by a pipe. All air from the system is exhausted via the exhaust valve in the compressor - so if you lower the suspension, all four bags are exhausted via the valve blocks back through the compressor exhaust valve.

The valve blocks at each end also allow the air bags at their end to be connected e.g. if the front left wheel is pushed upwards, the front right wheel is pushed down by the air being pushed from the front left airbag. This mimics a solid axles when off road and helps with traction.

The height of each wheel is monitored by a sensor attached to each corner. These are calibrated so that the suspension control module knows where each is. If a sensor is changed, the system needs to be calibrated. The suspension control module is above the driver's feet on the front right A-pillar base. You can access it via the footwell.

If the air dryer in the compressor breaks down, it can cause the drying medium (white powder) to be pumped around the system. This then causes the valves to not be seated correctly and then they leak.

If the exhaust valve stops working, the system can't lower. A symptom is that when asked to lower, the vehicle will then go up to off road height. This is because the system knows it's asked to exhaust air to lower but doesn't see the lowering happen - it doesn't monitor the exhaust valve directly. If no lowering happens, the system assumes you are bottomed out on something so it raises the suspension to allow you to drive off the obstacle.

I think that's it in basic terms.

Simple!  2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

Last edited by RRSTDV8 on Thu Jun 04 2020 12:33pm. Edited 1 time in total

In terms of failures, leaking air bags are rare - they are robust items unlike the original system back in the P38 days.

Valve block issues do happen and is usually down to stuff on the seals.

The compressor exhaust valve isn't a serviceable item so if it fails, it's a new compressor. The air dryer is serviceable. The air inlet filter doesn't usually cause problems but it can do if it gets full of gunk.

Sensors do fail. One failing will throw an error light and give reduced performance. If two were to fail, the system would likely drop to the bump stops. This also happens if the calibration becomes corrupted. It's still driveable but it's not nice and is limited to low speed. 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

Thanks for the responses

i have recently replaced one of the levelling Arms on the OSR. and had to re-calibrate.
everything OK for a couple of Months

But now got amber triangle with codes C1A20-64 / U0421-68 / C1131-92
initially Bought a new End Plate for the Hitachi compressor ( i then realised i had an AMK )
so i bought a complete new unit from Bearmach ( excellent service , Inc Next Day delivery)
which i intend to replace tonight.

so my post was to cover all other angles , Just in case

thanks

keith

Can't find a U042168 but U042181 is invalid data from suspension control module. These comms errors can usually be ignored.

Quote:

C1A2064 Pressure Increase Too Slow When Filling Reservoir

Compressor fault

Reservoir pipe air leak

Reservoir air leak

Gallery pipe air leak

Intake filter
blocked/restricted

Intake pipe
blocked/restricted

Air suspension intake
silencer blocked/restricted

Corner valve stuck open

Pressure sensor fault

Quote:

C113192 Air Spring Air Supply

Unable to pressurize
gallery

Insufficient pressure from
compressor

Detached air pipe

Loose or burst air pipe

Reservoir valve block pipes
incorrectly installed
(unions reversed)

Pressure sensor fault

i got "U421-68 = Invalid data received from Ride level control Module.


will update shortly when new compressor is on

Replaced Compressor , all back to normal now
took on a test drive , initially created loads of errors , cleared those ( engine was cold though )
then on the same test Drive all ok , no Errors Generated.

Just Ready for Boris to open the Country then go on a long Journey to Properly test

Happy Days

Just for information on thread, I found my issue to be the Air receiver it had rusted out will pin holes on side nearest the subframe. Sorry about quality of pic but ensure you spray some washing up liquid around it.

Folks, some stuff here I discovered in my recent suspension investigations and resolutions. Bit of a read but might help resolve issues as you trundle through the problems. I found a lot of different issues were resolved from simply changing Orings in valve blocks.
Interesting to see Drobe's issue was an air receiver.

https://www.rrsport.co.uk/gallery/albums/u...solved.pdf

WexMan - that's a heck of a guide you put together there. Excellent job.  2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

Cheers, the funny thing is, same symptoms may result in a different root cause for others. Get the diagnostic tool out and break the problem down and try to corner that sneaky fu€&er

That’s really helpful. Thanks Wexman

WexMan, excellent job mate That should be a sticky

Great write up saved that to my reading list, thankfully don’t have any issues at the moment. Steve

2005 2.7 TDV6 HSE, ongoing project.
1998 Volvo V70 R auto FWD, mothballed future project.
1999 BMW Z3 (owned from new) garage queen.

No bother folks. Hope it helps someone out of a jam.