Big bang

is the noise my rear suspension bag made today when it popped Luckily I was stationary at traffic lights and not on the m/way fully loaded , which I will be on Sunday!!
so new airbags this w/end then , should be ok fitting new ones but I was wondering if I should be looking for any underlying problems which may have caused the failure.
Looking thru old paperwork , one bag was replaced about 3 yrs ago but it doesn't say which one. I cant remember any big impacts recently , it only has light off road use when i go shooting but tbh it has a sheltered life for a 4x4
Andy

maybe now is the time to go coil springs??!!

It did cross my mind , but it is useful being able to lift it a bit to get the towbar out of the banks as i come downhill.
I think that being a 7 seater there are type approval issues as well

ordered bags today £155 for a pair including new clips and express delivery.
Stealers quoted £450 and I would have to drive and pick them up

Might be worth looking at ride height sensors, if the compressor was pumping and shouldn't have been. That can overpressure the bags.

David

I too would suggest you make sure the compressor turns off when it should or else your new bags will also explode.

Change your ride height sensors, please. They can be bought from LRseries for £20+vat each, so why wouldn't you?

I did look closely at the sensors but i couldn,t see anything broken / missing. I was going to replace the bags and check again once the system is all up and running (and hopefully stopping)
The bag that blew was an original so its 10 yrs / 110k miles old , I have taken them both off and it was def the old one that blew. I'm hoping the ride height sensors will be ok.

fireman-andy said:

I did look closely at the sensors but i couldn,t see anything broken / missing. I was going to replace the bags and check again once the system is all up and running (and hopefully stopping)
The bag that blew was an original so its 10 yrs / 110k miles old , I have taken them both off and it was def the old one that blew. I'm hoping the ride height sensors will be ok.

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The very best of luck to you,

Dave

well , changed the bags today , allgoing well until i started the engine and only one side inflated. wiggled the ride height sensor and it cut in inflated a little then stopped.
so 2 new ride height sensors later and all seems well.
looking at the two old ones i think that only one side has been working and it got too much and went pop.
hopefully thats it sorted now. the ride seems a little harsh now but I guess thats new 'springs'
does anyone think its worth getting the sensors calibrated as per rave??

thanks for all the help
andy

fireman-andy said:

. the ride seems a little harsh now but I guess thats new 'springs'
does anyone think its worth getting the sensors calibrated as per rave??

thanks for all the help
andy

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Taking into acount what happened/the harsh ride and that u put new sensors it wouldnt hurt to calibrate them just to be sure. Usually is not necessary but for that u have to be very cautios when u replace them.

My advice is to go for a calibration...u'll sleep easyer after

Cautious how? Surely it is just a case of undoing the mounting screws and removing them?

David

David Pye said:

Cautious how? Surely it is just a case of undoing the mounting screws and removing them?

David

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thats what I thought , raised the rear to full height to give me room to work. unplugged the multiplug , and.......... hiss as the back settled onto the bumpstop
I never knew that
so I swapped them over no problem started the engine and the raise suspension light was still lit.and no movement So it was on the bump stops but the max height light was on:doh:
pushed the raise botton again to switch light off , pushed it again and the car lifted to full height. lowered back to normal height and seems about level test drive was ok if a little harsh (bit like winding up preload on a m/bike)
seems to be settling level and not going down so wonder if a calibrate will be worth the expense

David Pye said:

Cautious how? Surely it is just a case of undoing the mounting screws and removing them?

David

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I meant that if u want to be sure u don't need calibration is to make certain that the car standed on a straight and plain surface during the work therewith after u replaced the sensors u have to do some "tricks" using ORM and doors until the SLABS ECU "accepts" the new sensors.....a kind of "manual calibration"............... That's what I know............on a second thought do u think that those who wrote the workshop manual did it with bad intention?

"When the sensors are replaced or removed for any reason, a calibration procedure is required to recalibrate the
sensors and the SLABS ECU. The calibration procedure requires the use of TestBook and calibration blocks to set
the axle to chassis height to a known value."

Not doing this could lead to "big bangs"....IMO

My understanding is that assuming you start with a car at normal height, disconnect the the battery negative lead so disabling the sls system, then replace the ride height sensors, then reconnect the battery lead.

No calibration should be required. My guess would be the blowout was caused by a faulty sensor sending bum info to the slabs ecu, so over pumping occured. This shouldn't have changed any element of calibration, in my book.

The key with all these systems is to disable them BEFORE disturbing them.

thebiglad said:

My guess would be the blowout was caused by a faulty sensor sending bum info to the slabs ecu, so over pumping occured. This shouldn't have changed any element of calibration, in my book.

The key with all these systems is to disable them BEFORE disturbing them.

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In this case dont u think that the SLABS ECU has an error code in it which could mess up the initial calibration?......or from some reason the ECU went mad and ordered the overpumping without faulty sensor?

My doubts came when fireman-andy said that " the ride seems a little harsh now....."

I'd say that it would be healthy just tu put the calibration blocks in to see if the level isnt too high from the start..........I might be a little(or more) paranoic on this

sierrafery said:

In this case dont u think that the SLABS ECU has an error code in it which could mess up the initial calibration?......or from some reason the ECU went mad and ordered the overpumping without faulty sensor?

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No, I wouldn't think so, to be honest. Apart from the sensor going open or short circuit, any other value would be seen as 'valid' and it would try to adjust the height accordingly.

I am certainly not aware of anything that needs to be done to make it 'accept' new sensors - you can just change them over. It will assume that the values from the new sensors will track in exactly the same way the old ones did and will adjust accordingly.

I certainly replaced mine this way. I did exactly what thebiglad suggested - remove the battery connector, replace sensors, replace battery lead. It doesn't really matter whether it is on level ground etc at the time you do the replacement as far as I can see. One of two things will happen:

Sensors near enough to originals to not need calibrating - no problem.

New sensor values are significantly different to older ones - should be calibrated otherwise risk of bags exploding.

I'd say that it would be healthy just tu put the calibration blocks in to see if the level isnt too high from the start..........I might be a little(or more) paranoic on this

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No, that seems very sensible to me, especially if there is a change in handling.

All I am disputing is the necessity to do anything to make the ECU 'accept' new sensors - not the advisability of performing a calibration.

David

I AGREE WITH EVERYTHING YOU SAID.........I was just exposing pretty much unlikely events....... SLS works in mysterious ways:brick:... sometimes........as we can see from the amount of related postings

To avoid testbook calibration in this case(the harsh ride) remains only a test to do......to activate ORM and see what difference it makes......if the difference is very small then I'd say that the bags are too inflated in normal mode and that's the reason of harsh ride(recalibration recommended).......if the difference between ORM and normal height is the standard one ....... I rest my case

I think the 'harsh'(firm is probably better) ride is just the fact that both bags are now working in stead of one . I think the ride height sensor on the side that never popped was faulty and caused the otherside to do all the work, coupled with the fact it was the original bag it couldn't take the strain and popped.
the car sits level and raises nicely in ORM, body roll is much reduced when driving.
This is my 1st disco and assumed the slightly soft wallowing ride was due to it being a 4x4 and no ace when it was more likely due too only one side of the suspension working properly
thanks for all of the responses
Andy

Good to hear that it's Ok, believe it or not Im pleased when I'm not right because the faults I describe are the meanest ones.....just pls don't believe that only one height sensor could work independently.