REAR SUSPENSION AIRBAGS

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Hirsty69

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S20 1aj
Hi,

Any help, advice or suggestions much appreciated.

I have a 54 plate Disco 2 which has just been in to the garage for MOT and a service. I took the opportunity to ask them to replace both rear suspension airbags. The nearside bag seemed to have a leak and the arch rested on the tyre when it was parked, but lifted up about 30 seconds after starting.

I bought two airbags from Hong Kong via ebay, which the garage fitted. As soon as the car was lowered, the nearside bag blew with a massive bang (see pic). We thought "cheap rubbish, lesson learned". However, garage ordered a genuine replacement bag, fitted it, lowered it and it went bang again, but this time blew off a piece of the solid plastic at the bottom! I haven't got a pic of that one, but have highlighted the area on the second pic. The garage put the old bag back on the offside, because it appeared sound, and swapped the second Hong Kong bag to the nearside - bang again. The mechanic and I stood scratching our heads. He phoned one of his contacts who deals solely with 4x4s. He suggested it may be the sensor arm, which cuts off the airflow when the bag is properly inflated. However, the arm seems to move freely and the airflow stops when the arm is manually extended. We put the original airbag back on, the one which allows the arch to rest on the tyre, and it's not blown.

I have also noticed that after driving there is a buzzing noise, which I've been told is a "minor leak on the compressor" and not to worry. It seems to me that there is too much pressure being sent to the new nearside bags, so they blow, but the leak on the old one allows the pressure to escape so it doesn't!

HELP!!!
 
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I am no expert on SLS having fitted coils to mine for overlanding, but it strikes me that your theory seems sound. Too much air to the affected side and the original only survives because of a leak.
This implies that the compressor may be running continuously, and I note the hissing noise and the inadequate diagnosis that it is a "minor leak on the compressor" and the dodgy advice not worry about it. The compressor is not designed to run continuously and will eventually burn out if not given the chance to cool down.
You do not mention if the calibration of the sensors has been checked. I would start there.
If thee was a fault with the compressor system I would have expected a warning light and some codes, but if the calibration is correct then I guess you need to look inside the compressor casing to check out the relevant air supply control valve and maybe the exhaust valve.
 
how did they fit them ,they come rolled over the bottom,if thats pulled out to fit the bag then lowered back down so bag folds over on it self it may well blow off,it could only break the bottom plastic circled in red by bad fitting
 
Si Click said:
I am no expert on SLS having fitted coils to mine for overlanding, but it strikes me that your theory seems sound. Too much air to the affected side and the original only survives because of a leak.
This implies that the compressor may be running continuously, and I note the hissing noise and the inadequate diagnosis that it is a "minor leak on the compressor" and the dodgy advice not worry about it. The compressor is not designed to run continuously and will eventually burn out if not given the chance to cool down.
You do not mention if the calibration of the sensors has been checked. I would start there.
If thee was a fault with the compressor system I would have expected a warning light and some codes, but if the calibration is correct then I guess you need to look inside the compressor casing to check out the relevant air supply control valve and maybe the exhaust valve.
Click to expand...

Thanks so much for the speedy response and helpful suggestions :)

The tyre place where I had the front nearside tyre changed, just before the MOT, said he thought he heard a leak on the rear nearside tyre. There wasn't, but there's obviously a leak of air around there, almost certainly the bag.

The advice about the compressor came from a guy whose own Landy made the same noise and he said he'd been driving round in his for over three years!

The garage who did the MOT aren't Landy specialists, so I'll investigate garages round Sheffield who may have a bit more expertise to look at calibration of the sensors, but might be worth just replacing them - less than £30 a pair on ebay, UK supplier.

If it were a fault on the compressor, wouldn't both bags blow? Maybe not at the same time - path of least resistence, but seems odd that three blew on the nearside, but the offside bag was happy as Larry. Unless different valves in the compressor serve the bags individually? (Please forgive my ignorance!) Before the MOT, the "three amigos" were a regular occurrence (TC, ABS, and the Hill Descent lights), but that seems to have been rectified now and was almost certainly unrelated to the bags. No other warning lights on the dash.

Thanks for taking the time to read my waffling :)
 
Hi,

Thanks for the speedy reply!

All three of the bags arrived and were fitted "rolled over the bottom", they were not expanded and folded over. Not ruling out bad fitting, but it seems unlikely. If the compressor is not cutting out when the bag is fully inflated, either because of a faulty sensor or the compressor, it would take the path of least resistance to blow - the band at the top of the bag on the two from Hong Kong and the plastic at the bottom of the UK one, wouldn't it???
 
If the sensor would not make the compressor to cut out you'll see that side going much higher than the other first but this was also covered by LR as the compressor has a pneumatically operated mechanical pressure valve which should release the air before the bag blows (as long as it's not stuck closed).

The other theory with a leak which saved the first bag is not valid either cos this would have kept the compressor working over time and there is a protection for that too which cuts the compressor feed on a "exceeded duty cycle'' default then the warning lamp comes on and the comprssor will get feed only after the fault code is cleared

something very strange is going on there, IMO not system related
 
Hirsty69 said:
If it were a fault on the compressor, wouldn't both bags blow? Maybe not at the same time - path of least resistence, but seems odd that three blew on the nearside, but the offside bag was happy as Larry. Unless different valves in the compressor serve the bags individually? (Please forgive my ignorance!) Before the MOT, the "three amigos" were a regular occurrence (TC, ABS, and the Hill Descent lights), but that seems to have been rectified now and was almost certainly unrelated to the bags. No other warning lights on the dash.
Click to expand...

There is a separate air supply valve for each bag. But as I alluded to, and others have stated, if there is a system fault then you should have a warning light and fault codes. You need to get the codes read by a decent LR specific diagnostic reader - Nanocom and Hawkeye are the best known. Avoid an "expert" with an OBDII reader as they do not work on the TD5 D2. You might want to think about buying your own as it will save money in the long term. About the cheapest option is the Foxwell NT530 with the Jaguar Land Rover software package (around £140). A suitable diagnostic tool will also calibrate the sensors. BTW even if you buy new sensors, they will still need to be calibrated.

It is because of the potential for difficult to diagnose and fix faults like this occurring somewhere remote that I have coils. The peace of mind was worth the loss of the benefits air suspension brings, and I do not miss either the air bags or the ACE.
 
Hirsty69 said:
Hi,

Thanks for the speedy reply!

All three of the bags arrived and were fitted "rolled over the bottom", they were not expanded and folded over. Not ruling out bad fitting, but it seems unlikely. If the compressor is not cutting out when the bag is fully inflated, either because of a faulty sensor or the compressor, it would take the path of least resistance to blow - the band at the top of the bag on the two from Hong Kong and the plastic at the bottom of the UK one, wouldn't it???
Click to expand...
youd have noticed an over fully inflated bag the arse end of the car would be stuck up in the air,if thats the case theres an answer
to snap the bottom plastic piece the bag must have been trying to twist
 
Si Click said:
There is a separate air supply valve for each bag. But as I alluded to, and others have stated, if there is a system fault then you should have a warning light and fault codes. You need to get the codes read by a decent LR specific diagnostic reader - Nanocom and Hawkeye are the best known. Avoid an "expert" with an OBDII reader as they do not work on the TD5 D2. You might want to think about buying your own as it will save money in the long term. About the cheapest option is the Foxwell NT530 with the Jaguar Land Rover software package (around £140). A suitable diagnostic tool will also calibrate the sensors. BTW even if you buy new sensors, they will still need to be calibrated.

It is because of the potential for difficult to diagnose and fix faults like this occurring somewhere remote that I have coils. The peace of mind was worth the loss of the benefits air suspension brings, and I do not miss either the air bags or the ACE.
Click to expand...

I have a Foxwell NT510 and it has been very helpful - obviously the D2 doesn't throw half as many codes as the other later-model cars I use it for (I have the LR and VAG software loaded). The Foxwell has decent support and with the internet forums and a bit of controlled playing around you gradually pick things up. One day these diagnostic devices will be user-friendly for the average Joe (some of the language and terminology needs a bit of work). Would like to get a Nanocom, but price was a tad too high and I wanted something I could use for different makes of vehicles.
 
jamesmartin said:
youd have noticed an over fully inflated bag the arse end of the car would be stuck up in the air,if thats the case theres an answer
to snap the bottom plastic piece the bag must have been trying to twist
Click to expand...

This certainly makes sense - would have introduced torsion as bag inflated and I noticed the tear at the top in the pic. Hard to imagine someone installing it in a twisted position (or maybe not locking the bayonet end at the bottom to start with).
 
Last edited:
jamesmartin said:
youd have noticed an over fully inflated bag the arse end of the car would be stuck up in the air,if thats the case theres an answer
to snap the bottom plastic piece the bag must have been trying to twist
Click to expand...

This certainly makes sense - would have introduced torsion as bag inflated and I noticed a tear at the top of the bag. Hard to imagine someone installing the bag in a twisted position to start with, or maybe just not locking the bayonet end of the bag at the bottom with a quarter turn to start with).
 
Intestinalworm said:
I have a Foxwell NT510 and it has been very helpful - obviously the D2 doesn't throw half as many codes as the other later-model cars I use it for (I have the LR and VAG software loaded). The Foxwell has decent support and with the internet forums and a bit of controlled playing around you gradually pick things up. One day these diagnostic devices will be user-friendly for the average Joe (some of the language and terminology needs a bit of work). Would like to get a Nanocom, but price was a tad too high and I wanted something I could use for different makes of vehicles.
Click to expand...
My Foxwell 520 is great and has just helped me solve a problem on Wifey's Citroen Pluriel at minimum cost and effort. diagnosed it right off. (Lambda sensor after the cat). SF warns that a Nano seems to get the wheel sensors mixed up and that happened to me when I took it to a LR garage. They cost me both time and money through that. don't know which diagnostic they used but they only managed to get the fault to the right axle, no further!
 
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