Go for coils springs or can it be sorted?

[NeilF]

Disco 2 facelift, 2002, 7 seat. I've done a search of the forum, but didn't find an answer to my problem.

I'm having trouble with my air springs. Both have been replaced, the last one about 2 years ago. They are not leaking - I can pump up the suspension and they stay up for days.

The problem is that the suspension goes down, on both sides, often just after parking. They will go up on driving, usually but not always. I can raise the suspension to off road hight without any problem and quickly.

I just got back from a short trip and it was down when I got out of the car
Then stayed up at normal hight for hours. Just drove over 6 or 7 speed bumps on our estate and by the last, the suspension was down to the bump stops (the back crashed down at the last). Used the off road setting to get it back up.

So it's unlikely a leak or compressor fault, and unless both ride hight sensors went out at the same time, it seems more of a management issue. I'd rather not go to coils if it was easy to sort.

 

[neilly]

Hi NeilF

Have you tried pumping up to max ORM and spraying with soapy water to see if there are any leaks.

Have a read of this as well, may be useful.
https://www.landyzone.co.uk/land-rover/disco-ii-air-suspension-–-the-definitive-guide.61211/

Cheers

 

[neilly]

Also,

To distinguish between a leak and system failure.

You can get valves and connectors to isolate the air side of the system.

Bay of flea number is.
271935006590


Cheers

 

[brian47]

Early faults on the air bags are notoriously difficult to diagnose. Sometimes they stay up for days, even weeks and other times they go down again in a matter of hours. The soap test isn't always conclusive.
You say that the last air bag was changed two years ago, this implies that you're changing them one at a time. This really isn't the way to go, in all fairness, they should be changed as a pair. Many owners have fallen into that trap over time and ended up pulling their hair out.
The other parts which can give troubles are the ride height sensors. In the grand scheme of things, they aren't expensive at about 25 quid each, but from your symptoms I'd say it was more of an "air side" problem.
I suppose there could be a leak on the pump or a valve, but if you're able to make the suspension go up and down with the ORM switch then it's probably unlikely that there's a fault on the electronics

 

[NeilF]

Guilty as charged on changing one air bag at a time. What is an "air side" problem? The fact that it went down after a couple of minutes driving over speed bumps might suggest sticking ride height sensors? I'd bite the bullet and get a pair of ride height sensors and two new air bags if I thought that would do it.

I went through all the posts on the SLS thread, but it didn't give me any clues

With the engine running, I bounced on the back bumper; the air pumped up and then released when I dismounted. Then with the engine off, I bounced on the back and the suspension dlflated in minutes

 

[brian47]

Guilty as charged on changing one air bag at a time. What is an "air side" problem? The fact that it went down after a couple of minutes driving over speed bumps might suggest sticking ride height sensors? I'd bite the bullet and get a pair of ride height sensors and two new air bags if I thought that would do it.

I went through all the posts on the SLS thread, but it didn't give me any clues

With the engine running, I bounced on the back bumper; the air pumped up and then released when I dismounted. Then with the engine off, I bounced on the back and the suspension dlflated in minutes

An "air side" problem is one which involves the compressor, air lines and air bags, any part that involves air, as opposed to an electronics side which would involve the SLABS ECU, ride height sensors, compressor motor and other electrical bits.
A "sticking" ride height sensor is unlikely unless one end has come loose, since one end is attached to the axle and the other to the chassis so that it can measure the distance between them and therefore the height of the body off the ground.
I had a problem where the suspension dropped just once, about three years ago. I didn't bother with trying to diagnose the problem, I just changed both of the air bags and I've had further trouble.
IMO the bags are relatively cheap, about 160 quid a pair and because they appear to be the first point of failure, it's worthwhile changing them at the first sign of trouble, or even as a "diagnostic" measure, you could at least then discount them if you have to go deeper into the working of air suspension system.

 

[NeilF]

I was thinking the same thing, though I'd thought of replacing the ride height sensors while I was at it. Dunlop air springs are only £55 each and the sensors £22. If that doesn't do it, i could think again. I would go straight to coil springs, but it's a 7 seater and I've read of insurance invalidation and I'm not sure of fooling the ECU bit.

 

[brian47]

I was thinking the same thing, though I'd thought of replacing the ride height sensors while I was at it. Dunlop air springs are only £55 each and the sensors £22. If that doesn't do it, i could think again. I would go straight to coil springs, but it's a 7 seater and I've read of insurance invalidation and I'm not sure of fooling the ECU bit.

A couple of points to note about the jobs:

• Disconnect the battery before you start unplugging the ride height sensors otherwise you could have to recalibrate the system afterwards. Make sure that you know the radio security code!
• When you fit Dunlop bags, They have push in connectors for the air lines. Make sure that you cut them absolutely square at the ends. Make sure that the pipe ends are clean and undamaged before assembly. Push them fully home before you pressurise the system. Before you start with the bags, check that you have two new clips with each bag.

 

[NeilF]

I'm trying to get my head round the fact that it can stay up for days, and yet go down within minutes, even with the engine running. What's the signal for the system to release the air from the bags? The height sensor is the easy answer, but is it sending the wrong signal to the ECU or is the ECU sending the wrong signal to the (?) valve block?

I've ordered the bags, but I'm convinced its something else.

 

[NeilF]

As an addendum, I cancelled the order for the bags because on the one hand, it will stay up for week, but on the other, if I bounce on the back bumper, it goes down in seconds and further, if I go over speed bumps, it will also go down, even when the engine is running. It goes down too fast for a leak. What can I try?

 

[Tony e]

Sounds like the valve block to me. Could be a solanoid. Can it be diagnosed like the p38, just a thought before you waste your hard earned

 

[brian47]

Sounds like the valve block to me. Could be a solanoid. Can it be diagnosed like the p38, just a thought before you waste your hard earned

Valve block?
The disco 2, unlike the P38 only has air suspension on the rear axle. The only components of the SLS air suspension system are:

• Two air bag springs
• Two Ride height sensors
• The SLABS electronic control unit
• The SLS Compressor unit which basically comprises of an electrically driven compressor and two electrically activated air valves to inflate/deflate the airbag springs.

I'm still of a mind that the problem lies with the air bag springs, although the OP seems convinced that the only way to remove the fault is change to steel coils.
As I've already said, in the early stages of trouble with the SLS, the air bags can present some strange symptoms. They can stay up for weeks if they're left alone and drop immediately if disturbed, but if one is convinced that only a change to coils can remove, not repair the fault then that will be the only possible way to go. Trying to "over-analyse" the fault will just muddy the waters.

 

[neilly]

I already suggested he try the isolation valves.

In this way he could blow the airbags up manually, leave them and also try his driving over sleeping policeman or jumping on the back of it and see if it stays up or not.

Not sure what else to offer as a suggestion.

Cheers

 

[NeilF]

I think this is the thing? Best price is about £150 - lot to pay on spec........

I'm not sure if it's true that a leak an drop the suspension on both sides immediately. When I have had leaks, it was one side, overnight.

ANR4869 | Valve Block - Ds2 Rear Air Suspensi

 

[NeilF]

I followed the link for the isolation valves, it's only £20 for the set - it wasn't clear how it's used but I'm guessing to comes with instructions. If I remove the whole air system from the equation, I can pull the valve block and clean it and still be mobile if it goes pear-shaped.

 

[neilly]

Give the guy on bay of flea a call, He probably has seen this before and may be able to give you a hint on what to try to diagnose the problem.

Cheers

 

[brian47]

Give the guy on bay of flea a call, He probably has seen this before and may be able to give you a hint on what to try to diagnose the problem.

Cheers

It does look like the OP has convinced himself that the only way to remove, not repair the fault is to change to coils. I'm still of a mind that it's nothing more than the bags.

 

[brianconwy]

It is strange for both sides to deflate if a bag has gone, unless two bags have gone. But then why would they stay up for days? Connecting up to a diagnostic unit allows the option of raising either side independently and trialling the valves etc.

 

[NeilF]

Well, I went back to first principles and sprayed with soapy water. Nothing. Then I jumped up and down on the back bumper and lo and behold! bubbles from one spring. So I'll buy a pair to replace both.

Still not sure why both sides go down though?

 

[meego]

Well, I went back to first principles and sprayed with soapy water. Nothing. Then I jumped up and down on the back bumper and lo and behold! bubbles from one spring. So I'll buy a pair to replace both.

Still not sure why both sides go down though?

First port of call is always the bags. Even a relatively new bag. They operate by "folding" into themselves and small stones or chips can get in there and erode them until they leak. I know a couple of guys who converted to springs and regretted it almost immediately. Its not an expensive, or difficult system to maintain by any manner of means.