Still got issues on 2007 E class estate rear self levelling air suspension.

[Baldbloke]

Is your newly fitted ride height lever, the one thats on the rear axle, adjusted to the correct length. Mine snapped and when I replaced it wasn't high enough so I had to adjust the length by trial and error.

Thanks for the reply. My plastic arm snapped a couple of years ago too. I replaced it with an upgraded Mercedes metal one. The height adjuster seems to be set as it’s fixed between the mounting plate which the sensor fits onto the body and the arm’s end which clamps onto the anti roll bar. The clamp fixing corresponds to a cut away on the roll bar so it looks like there’s no adjustment as such as it is pre-determined between the machining of the roll bar and the body fixing bolts
I did wonder if Star diagnostics has a capability to reset the sensor so that the air suspension can take more pressure, but that wouldn’t explain why the compressor needs to start up each time the engine is restarted.

I’m beginning to think there’s a leak that’s allowing the bags to mostly pressure up but not allowing the system to pressure up adequately for the proper ride height.
If there is a leak, and it’s at the valve(s) on top of the air springs it is odd that the springs don’t deflate completely after a few days.
I think it will have to return to the workshop for another soapy water test of all the pipe work joints

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[Dodipops]

I don’t think there’s a re learn or teach in of the height sensor.

There might be a calibration of the whole system but shouldn’t need done for either compressor or level sensor replacement

What happens when you try to lift it with the raise button in the car?

 

[Baldbloke]

I don’t think there’s a re learn or teach in of the height sensor.

There might be a calibration of the whole system but shouldn’t need done for either compressor or level sensor replacement

What happens when you try to lift it with the raise button in the car?

Hi, there is only air to the rear air bag units on my estate car. Steel coil springs on front. So it isn’t Airmatic as doesn’t have full air suspension. No ride height adjustment in car that I know of.


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[Dodipops]

I just done a compressor on 2008 211 and im sure it only had rear bags with a button inside to lift it?
Maybe not!

Have you got any form of diagnostics? In live data it should tell you actual and target heaight of the rear axle. The one I just done was 0mm.

 

[Baldbloke]

I just done a compressor on 2008 211 and im sure it only had rear bags with a button inside to lift it?
Maybe not!

Have you got any form of diagnostics? In live data it should tell you actual and target heaight of the rear axle. The one I just done was 0mm.

Hi again. I certainly haven’t seen a ride height adjuster button. There’s just a C/S (comfort and sport) which I don’t think does anything for ride height)
Mines a 2007 Elegance model
No, I don’t have any diagnostics. I’ve been considering Carsoft but was a little disappointed with one I bought for another make, and Star is astronomical in price




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[Dodipops]

Well I done a height sensor on a 221 s class fairly recently too so maybe I’m merging 2 systems together.?!

Without diagnostics it’ll be tough, the only thing you can do is swivel the bracket on the anti roll bar (while the car is on the flat)until the car gets to a reasonable height.

I assume you have the flat bit of the clamp against the cut out of the bar not the rounded u part?

 

[Baldbloke]

Well I done a height sensor on a 221 s class fairly recently too so maybe I’m merging 2 systems together.?!

Without diagnostics it’ll be tough, the only thing you can do is swivel the bracket on the anti roll bar (while the car is on the flat)until the car gets to a reasonable height.

I assume you have the flat bit of the clamp against the cut out of the bar not the rounded u part?

Yes, the flat bit of the clamp does correspond to the flat cut out section in the roll bar.
I’ll get the car back into the workshop tomorrow, jack up all four wheels and put the rear wheels on ramps to load them. Otherwise with wheels hanging it won’t want to allow air to feed into the bags. It will also give me another chance to check for leaks
Yes, I understand the S class has more buttons and functions over my E class. Mine seems complicated enough!


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[Baldbloke]

Is your newly fitted ride height lever, the one thats on the rear axle, adjusted to the correct length. Mine snapped and when I replaced it wasn't high enough so I had to adjust the length by trial and error.

How exactly did you adjust the length? I did wonder if my new (two years ago) replacement metal linkage was longer than the plastic broken plastic one it replaced.
Now the ride height has been a little low ever since the linkage first broke before the recent suspension collapse and before the bags were renewed. I’ll maybe try the (newish) linkage on the sensor arm’s first hole instead of where the original plastic linkage was fitted at the end hole.


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[millo777]

I'd suggest you jack the rear of the car up so the weight is off the rear wheels but they are just about touching the ground then activate the compressor with a jumper wire where the relay should be (between 30 and 87) .

This will remove and issues relating to the height sensor. It'll just activate the compressor and pump the springs up.

Let it run for 30 seconds the lower the car back onto the floor and let the engine run for 5 mins.

This should get the car back to the normal ride height.

You can do it without jacking the car if you're comfortable that the springs won't get damaged.

To make a jumper wire you only need 6 inches of 12awg wire and crimp a spade terminal on each end.

The point is, all the height sensor does is trigger the relay to turn on the compressor. Bypass that whole set up and you can check the compressor can pump up the springs. If it can't , then you can investigate further.

 

[Dodipops]

Just double checking that you have got the lever on the sensor at the top think it sits about 1-2 o clock.

It is possible to have the arm more like 5 o clock and still have the rod connected to the bar ok.

So arm on the sensor itself is at top pointing towards the back seats essentially.

 

[Baldbloke]

Just double checking that you have got the lever on the sensor at the top think it sits about 1-2 o clock.

It is possible to have the arm more like 5 o clock and still have the rod connected to the bar ok.

So arm on the sensor itself is at top pointing towards the back seats essentially.

Now this could be the issue. I’ll have to check this out.
When the sensor arm broke two years ago, the arm hung down as it wasn’t connected to anything. The rear of the car rose up so high the nose almost touched the ground. Because of this I had no datum/ reference which correct attitude the arm should have been reset to. It’s possible I set it up wrongly and I’ve copied my mistake ever since. The car had always sat a little low since that first incident, although not as low as presently. I’ll check and report back.

Although it’s a bit restrictive, I will see if I can take a photo to confirm it is sitting correctly - or not.


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[Baldbloke]

I'd suggest you jack the rear of the car up so the weight is off the rear wheels but they are just about touching the ground then activate the compressor with a jumper wire where the relay should be (between 30 and 87) .

This will remove and issues relating to the height sensor. It'll just activate the compressor and pump the springs up.

Let it run for 30 seconds the lower the car back onto the floor and let the engine run for 5 mins.

This should get the car back to the normal ride height.

You can do it without jacking the car if you're comfortable that the springs won't get damaged.

To make a jumper wire you only need 6 inches of 12awg wire and crimp a spade terminal on each end.

The point is, all the height sensor does is trigger the relay to turn on the compressor. Bypass that whole set up and you can check the compressor can pump up the springs. If it can't , then you can investigate further.

You mentioned this earlier, and I did look to try it out, but I had three problems. My relay was on the inboard side (and not the outboard side as kindly marked by you on my photo) at the very rear of the fuse box. It was really awkward to get to, let alone see any numbers on the holder base as a view is obstructed by the bulkhead.
The last issue was that the car did manage a pump up with the wheels up in the air just touching the ground but with everything connected. When I lowered it back down so the car was fully weight bearing and restarted the car there was an audible dump of air from the compressor end.
I don’t think I’ve got the sensor lever misaligned, but I have done more stupid things!

Thanks for all your inputs guys! It’s much appreciated


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[andym2]

I’ve got a 2008 S211 with the same suspension setup and a MaxiECU diagnostic that cost about £150. Pretty sure that can read all the sensor levels and stuff. I’ll plug it in and have a look later, then post the values so you have an idea of what they should be, if that’s of any help. MaxiECU seems ok for older cars like mine, but doesn’t support the very latest models. Having done a lot of DIY maintenance on my car I’d say some sort of diag tool is essential for these cars, otherwise you end up replacing a lot of things that aren’t broken to find the part that is. A lot of things need coding or calibrating too when parts are replaced.

My car has done over 225,000 miles now and I’ve had to reconnect the wires to the compressor a couple of times now after they’ve broken. Seems the compressor vibrates on it’s rubber mounts when it’s running and that breaks the wires near to the connector. Last time I replaced the connector as the break was too close to the connector to join the wires. Only a couple of quid from MB dealer, but you have to order the contacts and the connector shell as separate parts.

 

[Baldbloke]

I’ve got a 2008 S211 with the same suspension setup and a MaxiECU diagnostic that cost about £150. Pretty sure that can read all the sensor levels and stuff. I’ll plug it in and have a look later, then post the values so you have an idea of what they should be, if that’s of any help. MaxiECU seems ok for older cars like mine, but doesn’t support the very latest models. Having done a lot of DIY maintenance on my car I’d say some sort of diag tool is essential for these cars, otherwise you end up replacing a lot of things that aren’t broken to find the part that is. A lot of things need coding or calibrating too when parts are replaced.

My car has done over 225,000 miles now and I’ve had to reconnect the wires to the compressor a couple of times now after they’ve broken. Seems the compressor vibrates on it’s rubber mounts when it’s running and that breaks the wires near to the connector. Last time I replaced the connector as the break was too close to the connector to join the wires. Only a couple of quid from MB dealer, but you have to order the contacts and the connector shell as separate parts.

Thanks for taking the time to reply. If I get this sorted I’ll probably go down the route of spending some cash on diagnostics.
My car has only done 71,000 miles and I bought it from a friend who was the original owner. So apart from slightly corroded suspension components the car is in great condition apart from this suspension problem.
The new replacement compressor (along with the relay) is audible and a lot busier than the original compressor. The wiring seems good with my limited testing abilities. My concern is that I’m not sure if the new compressor should be working so much. It appears to run for a while on each start up. Today I’m going to check again for leaks as well as look to see if the sensor arm is positioned correctly


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[Baldbloke]

Now this could be the issue. I’ll have to check this out.
When the sensor arm broke two years ago, the arm hung down as it wasn’t connected to anything. The rear of the car rose up so high the nose almost touched the ground. Because of this I had no datum/ reference which correct attitude the arm should have been reset to. It’s possible I set it up wrongly and I’ve copied my mistake ever since. The car had always sat a little low since that first incident, although not as low as presently. I’ll check and report back.

Although it’s a bit restrictive, I will see if I can take a photo to confirm it is sitting correctly - or not.


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Unfortunately the arm is at the 2 O clock position, and the clamp is positioned correctly

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[andym2]

Ok... I tried MaxiECU and is doesn't have as much info as I thought. Although it can see the self levelling suspension ECU all it seems to be able to do is read the version number and any stored faults. It also has Air suspension on the menu, but that gives a waring about the ECU being an unknown controller version. It looks more like it's expecting the full airmatic ECU as it has front and back, rather than just the rear. Still, it does show the output voltage from the level sensor as 2.9v and the vehicle height as 2mmm.

I've also got an old iCarSoft AET-1 scanner. You can't seem to buy these anymore and their website has disappeared, but it does give a bit more detail. I've uploaded a few screenshots to a gallery...View media item 8321View media item 8322View media item 8323View media item 8324View media item 8325View media item 8326View media item 8328View media item 8329

 

[andym2]

If you can find a way of measuring the level sensor output voltage, maybe you could adjust the arm position so you get about 2.5v at the correct ride height?

 

[Baldbloke]

I’ve got a 2008 S211 with the same suspension setup and a MaxiECU diagnostic that cost about £150. Pretty sure that can read all the sensor levels and stuff. I’ll plug it in and have a look later, then post the values so you have an idea of what they should be, if that’s of any help. MaxiECU seems ok for older cars like mine, but doesn’t support the very latest models. Having done a lot of DIY maintenance on my car I’d say some sort of diag tool is essential for these cars, otherwise you end up replacing a lot of things that aren’t broken to find the part that is. A lot of things need coding or calibrating too when parts are replaced.

My car has done over 225,000 miles now and I’ve had to reconnect the wires to the compressor a couple of times now after they’ve broken. Seems the compressor vibrates on it’s rubber mounts when it’s running and that breaks the wires near to the connector. Last time I replaced the connector as the break was too close to the connector to join the wires. Only a couple of quid from MB dealer, but you have to order the contacts and the connector shell as separate parts.

Ok. I’ve carefully checked every join for leaks. There’s no leaks.
I’ve loosened the sensor arm on the rear anti roll bar to play around with the levels. What I found so far was that if the sensors lever was turned anti-clockwise (ie nearly vertical/upright or 12 o clock from its proper 2 o clock position) the compressor vented and the car lowered. However even bringing the lever down to touch the rear driveshaft fails to lift the car. So the car is presently even lower than it was before.
However both sides are equally low and when it was slightly up previously, it was equally up. I can only surmise there’s an electrical fault and that With my nil knowledge on electrics will be unable to find it.

The new compressor fails to start up even when I lower the arm to ask for extra ride height. Somethings amiss.





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[Baldbloke]

Ok... I tried MaxiECU and is doesn't have as much info as I thought. Although it can see the self levelling suspension ECU all it seems to be able to do is read the version number and any stored faults. It also has Air suspension on the menu, but that gives a waring about the ECU being an unknown controller version. It looks more like it's expecting the full airmatic ECU as it has front and back, rather than just the rear. Still, it does show the output voltage from the level sensor as 2.9v and the vehicle height as 2mmm.

I've also got an old iCarSoft AET-1 scanner. You can't seem to buy these anymore and their website has disappeared, but it does give a bit more detail. I've uploaded a few screenshots to a gallery...View media item 8321View media item 8322View media item 8323View media item 8324View media item 8325View media item 8326View media item 8328View media item 8329

Hi Andy, thanks for your help. I’d just posted before seeing your most recent offering.
It is looking like Millo might be correct on the wiring front as moving the sensor arm is having little to no effect on ride height.

EDIT:


The ends of the lower wishbones are sitting on axle stands so I would have thought that would have allowed air in on demand.

With my phone I’m unable to see your pictures but appreciate the effort.

I didn’t realise there was an ECU involved too, but I think it’s time to try to get it to someone whose good on electrics and Mercedes.


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[andym2]

The ECU/controller is N97 and it's in the passenger footwell. Wiring diagram says there's a 4 wire connection from that to the rear axle level sensor.