Benji disco · Jan 17, 2020

Hi,

im a little lost with the rear suspension, occasionally, usually after going down a long hill the rear suspension gives up and goes onto its bump stops?

this is on the left side, the right(drivers) isnt as bad but does lower as well.

what could cause it to drop onto the bump stops while driving?

holds air and the car is level at all other times and works great, along with the rear lift etc. i just dont understand this occasional drop?

sierrafery · Jan 17, 2020

Hi, disconnect the battery first then unplug the height sensors and check for cracks or corrosion, if they seem OK give them some contact spray... might be a bad contact there cos those connectors are a common failure hence many repair kits sold: https://www.ebay.co.uk/itm/151466538011

Interceptorxj · Jan 19, 2020

I would say faulty height sensor. One of mine went once and it appeared OK when you looked at it but when I disconnected it to check it I found that the centre mechanism was very stiff /seizing and the plastic arm was just spinning on the centre shaft without moving it. Mine was stuck in the high position even though the arm was connected and in the normal position and it kept over inflating the bag. Your's could be stuck in the lowering position.

Benji disco · Jan 20, 2020

Interceptorxj said:
I would say faulty height sensor. One of mine went once and it appeared OK when you looked at it but when I disconnected it to check it I found that the centre mechanism was very stiff /seizing and the plastic arm was just spinning on the centre shaft without moving it. Mine was stuck in the high position even though the arm was connected and in the normal position and it kept over inflating the bag. Your's could be stuck in the lowering position.

would that cause intermittent failure? also do they need calibrating or anything if i swap it with another, or is it just a battery disconnect and swap it out plug n play.

sierrafery · Jan 20, 2020

If you disconnect the battery and the sensors on the vehicle are genuine and you swap with genuine in most cases calibration is not needed, if the sensor are different brand aftermarket then it's a matter of luck, it's possible to need calibration or not

though the issue being intermittent IMO it's rather a bad contact issue as i explained in my previous post

Interceptorxj · Jan 21, 2020

Benji disco said:
would that cause intermittent failure? also do they need calibrating or anything if i swap it with another, or is it just a battery disconnect and swap it out plug n play.

If the shaft is sticking sometimes and other times not then yes. Just disconnect the lever and push it up and down to see if it is physically operating ok. If you disconnect the battery before removing then they are plug and play.

sierrafery · Jan 21, 2020

Interceptorxj said:
If the shaft is sticking sometimes and other times not then yes.

Can you explain please how would the sensor's shaft stick against the force of the body's weight? the sensor's arm which is attached to the shaft is moved by the radius arm.... i can't imagine how the sensor can stick against that force or if it does the sensor would brake in no time

Interceptorxj · Jan 21, 2020

The plastic sensor body has a steel spindle in the middle, this spindle has the plastic actuator arm press fitted to the spindle shaft which operates the spindle movement. On one of mine the centre spindle which normally rotates freely in the sensor body became very stiff and instead of the spindle moving the pressed on arm started to turn on the spindle shaft. The spindle was stuck in the raise position even though the actuator arm was still attached in normal height. It kept on inflating the airbag to maximum. I only found the problem after I disconnected the linkage to fit a new sensor I manually operated the arm which showed it just rotating on the spindle shaft instead of the spindle turning in the housing like the new replacement.

Benji disco · Jan 22, 2020

Thanks for the help so far, but this problem is getting a little more complex and bizarre.

i have checked out the cables and continuity tested with a meter all good, even if i move the cables about etc, the back left sensor appears to be working ok and i cant get it to fail, if i fool it the air bag raises / lowers exactly as it should.

but yet again steep incline and it gives up, although i noticed this time that the exhaust air is constantly on for the back left airbag, it tries to pump up but obviously cant. it continues in this cycle until the compressor says its ran for too long and shuts off, meanwhile the nearside back is on its bump stops.

if i switch the car off/on the compressor will start but no difference still exhausting.

if i leave the car for 20 minutes or so the bag pumps up and all is good again until i go down the exact same hill again! (all other hills are fine - its just this one!)

am i just better off sticking coils in? i cant get the bag to excessively exhaust by fooling the ride height sensor its bonkers or is it a sticky exhaust valve but that should show up with me fooling it... im a little lost for what next now

ronsealdeath · Jan 22, 2020

There is a couple of fail points, and it could be a leaking bag. Far more likely (if not the sensor) is a stuck valve in the pump. This valve releases air into the exhaust to lower the bag on each side. A sticky valve on open, would cause the compressor to stay on due to not enough pressure getting to the bag. They can be looked at and lubricated with something appropriate to unstick them. They are in the black box at passenger side. If beyond, then a good used compressor would be a cost effective option to sort it.

Benji disco · Jan 22, 2020

ronsealdeath said:
There is a couple of fail points, and it could be a leaking bag. Far more likely (if not the sensor) is a stuck valve in the pump. This valve releases air into the exhaust to lower the bag on each side. A sticky valve on open, would cause the compressor to stay on due to not enough pressure getting to the bag. They can be looked at and lubricated with something appropriate to unstick them. They are in the black box at passenger side. If beyond, then a good used compressor would be a cost effective option to sort it.

i think the bags are fine because they hold air, and i cant get the exhaust valve to stick open if i mess about with the sensor and fool the compressor into raising / lowering so i'm not 100% convinced on that one, and by time i can get a meter out to test everything its all working again.

there is a particular scenario where it exhausts i just cant replicate it on the drive, a spring conversion kit is like £180 then i dont have to worry about it ever again as this could just be the start of airbag woes, i.e first the compressor, then the bags or piping etc etc. just not sure if i would be doing the right thing removing SLS though

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