Disco 2 Does your Discovery 2 also lower at traffic lights?

MAF Diver · Jun 25, 2024

I've got ACE and SLS (airbags) in my D2a V8 4L and I've noticed two things when stopping at traffic lights:

1) Sometimes the rear will lower a little. It looks like the front is raising but obviously that can't be since it's got coils, right? Or can ACE do this?

Is that normal? Does yours do it too? Or is it a sign that the SLS is failing?

(I had the rear drop completely to the very lowest setting the other day when driving on a lot of curves and speed bumps. It then raised up later and I've never found it sagged in the morning.)

2) Sometimes shortly after braking to stop in traffic, the front will raise up very quickly like it's getting unstuck from something.

Is that an issue with shocks (probably the original ones still, after 75,000 miles on the clock), or is it something to do with ACE?

Andy Warren · Jun 26, 2024

Hi, this sounds like you have a leak somewhere. Mine had some odd behaviour in that it would never sink overnight even if it was left unused for a week but when driving & not always it would drop to the bump stops but if I stopped, turned the engine off then restarted it, it would re-inflate the air bags. It turned out there was a small hole in one of the bags but it always occurs under the folds where you can't see ! Try spraying soapy water on the bags/pipes etc to see if you can detect any leaks. DO NOT put any body parts between the trucks body or chassis e.g over the top of the rear wheels to spray the bags or get underneath it without axle stands/jacks in place to stop the body dropping, people have been seriously injured where the body has dropped unexpectedly ! (New drivers side air bag cured mine).

1988smithy · Jun 26, 2024

I'd be inclined to fit new bags as a matter of course depending on age and mileage covered by current ones

MAF Diver · Sep 17, 2024

So, I've got an update

Andy Warren said:
Hi, this sounds like you have a leak somewhere.

1988smithy said:
I'd be inclined to fit new bags as a matter of course depending on age and mileage covered by current ones

I changed the bags! (And also the shocks and front coils.)

Now I don't get those jolts anymore (problem 2 from my OP), but I still get problem 1:
- At traffic lights the rear gets lowered as I'm standing there with the brake depressed.

Then while driving it has to raise.

This seems really unnecessary? Or do all of them with SLS do it?

meego · Sep 17, 2024

MAF Diver said:
So, I've got an update

I changed the bags! (And also the shocks and front coils.)

Now I don't get those jolts anymore (problem 2 from my OP), but I still get problem 1:
- At traffic lights the rear gets lowered as I'm standing there with the brake depressed.

Then while driving it has to raise.

This seems really unnecessary? Or do all of them with SLS do it?

No, they don’t. Height should be consistent. You have either a compressor or height sensor fault if you have fitted new airbags. Or a leaking pipe somewhere !!

MAF Diver · Sep 26, 2024

meego said:
No, they don’t. Height should be consistent. You have either a compressor or height sensor fault if you have fitted new airbags. Or a leaking pipe somewhere !!

How do I go about assessing this?

Leaking pipe: don't think so because the car doesn't lower when parked overnight (or longer).

Compressor or height sensor issue: could be. Someone also said it could be ECU?

But how to I eliminate/test? No errors come up in my OBD2

meego · Sep 26, 2024

MAF Diver said:
How do I go about assessing this?

Leaking pipe: don't think so because the car doesn't lower when parked overnight (or longer).

Compressor or height sensor issue: could be. Someone also said it could be ECU?

But how to I eliminate/test? No errors come up in my OBD2

Raise the bags to full height and spray with soap/water mix and look for bubbles. (I know you have installed new, but better to rule them out) Trace the pipes and connections back to the compressor and check these in the same way. The compressor has seals and connections that can leak, so check there in the same way. Refurb kits for the compressor are available if that proves to be the issue. I’m not sure on an ECU being the issue or how to confirm this if your diagnostic isn’t picking it up. Perhaps a Nanocom would be better if that’s an option.

Polski Boschski · Sep 26, 2024

Sell it.
Road tax cost is enough to not bother with them anymore

sierrafery · Sep 26, 2024

MAF Diver said:
How do I go about assessing this?

Leaking pipe: don't think so because the car doesn't lower when parked overnight (or longer).

Compressor or height sensor issue: could be. Someone also said it could be ECU?

But how to I eliminate/test? No errors come up in my OBD2

OBD2 is useless in this case and it's not about a fault code as long as you didnt get the warning lights on provided they all work well on ignition self test. If you have a feeling that the front is raising not the back dropping it can be caused by ACE misbehaviour(unless it's just an impression and in reality the rear is dropping) so you must eliminate one suspect

1. Remove the ACE relay (R14) and drive it so to see if it's better or not(don't bother with the warning light, it will go out after you refit the relay) ...
2. if no change with ACE disabled remove fusible link FL9 to disable the SLS and see then(also neglect the warning lights)

in one of these cases the symptom should go away just tell when

MAF Diver · Oct 4, 2024

I didn't have a chance to mess with the relays yet, but:

sierrafery said:
If you have a feeling that the front is raising not the back dropping it can be caused by ACE misbehaviour(unless it's just an impression and in reality the rear is dropping)

I think it's the rear dropping!

I drove with my windows down and radio off, and I could hear the SLS hissing when stopped at traffic lights as the "front raises" (but the rear drops in reality)

It sometimes happens when I'm maneuvering when parking as well

Do you think it's a faulty ride height sensor? My car is sitting level more or less at the back (left side 505mm and right 506mm hub center to arch), but the Nanocom heights to achieve that are 179 left and 167 right. So quite a big difference...

MAF Diver · Oct 4, 2024

meego said:
Raise the bags to full height and spray with soap/water mix and look for bubbles. (I know you have installed new, but better to rule them out) Trace the pipes and connections back to the compressor and check these in the same way. The compressor has seals and connections that can leak, so check there in the same way. Refurb kits for the compressor are available if that proves to be the issue. I’m not sure on an ECU being the issue or how to confirm this if your diagnostic isn’t picking it up. Perhaps a Nanocom would be better if that’s an option.

Will do and will report back. I borrowed a Nanocom for a week! It doesn't show SLS errors, just an ACE one (accelerometer values not changing, don't think that's relevant)

If it's a leak as you suspect somewhere:

Could be that air is leaking from one side and the other lowers to accommodate?

Or I've also heard that vents can get stuck open? Or stuck closed?

Polski Boschski said:
Sell it.
Road tax cost is enough to not bother with them anymore

I'm in Australia mate, still good to have 'em here

meego · Oct 4, 2024

MAF Diver said:
Will do and will report back. I borrowed a Nanocom for a week! It doesn't show SLS errors, just an ACE one (accelerometer values not changing, don't think that's relevant)

If it's a leak as you suspect somewhere:

Could be that air is leaking from one side and the other lowers to accommodate?

Or I've also heard that vents can get stuck open? Or stuck closed?

I'm in Australia mate, still good to have 'em here

There is a filter for the SLS as well mate. I don’t think this will be your issue, but it’s worth giving it a clean out. It sits behind the rear near side light cluster. Remove the cluster and you will see a black canister with a sponge filter inside it.

sierrafery · Oct 4, 2024

MAF Diver said:
I borrowed a Nanocom for a week!

Then when it's on even level set it to coils and go for a ride to see if it behaves the same or not cos if it's about a leak it will lower but not rise back, if while it's set to coils it behaves normally and doesnt drop it's certainly not a leak but some strange management issue like when the ECU "thiks" that a door was opened an load remove from the vehicle or a height sensor is on it's way out became extra sensitive hence those reading differencies too at the same level

Disco 2 Does your Discovery 2 also lower at traffic lights?

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