Help on LAD air removal...

[StoyanG]

Hi guys,

So the other day I've done a repair on my right LAD shock, replaced all of the rubber rings and stuff, reassembled it with putting some oil in the shock, and then tried bleeding the air out of it, by making the rear of the car going up and down with the valve, but no luck.
So any other ideas on removing it, because the car is higher on the right and it's unstable as hell.
On the net I didn't manage to find something more than - :put some weight and start the car" ...

Cheers

[shogun]

lift the rear of the car that both rear wheels are hanging free, that cause the shocks to expand,

start the engine and let it run so that Pentosin can circulate. At the bottom of the small part of the LAD shock is a small bleeding hole which opens when the rear of the car is lifted and the rear wheels are hanging free

[StoyanG]

Shogun, could you show me a pic of the bleeding hole on the shock?
Or you mean the bleeding valve on the regulator?

[shogun]

http://bmwe32.masscom.net/gavin/a9.jpg
http://bmwe32.masscom.net/gavin/A10.jpg

The ride height is adjusted to a predefined height (distance from the edge of the rim to the edge of the wheel well) with the pre-defined weight in the trunk. Both values can be found in the Bentley Repair Manual and they are also mentioned on this board. Use the search with 'LAD ride height'.

Here is a trick from my own experience that should make the job easier. You should loosen the lever on the stabilizer so you can change the adjustment. If you move the lever forward, in the driving direction, you also move the lever on the control valve forward and the result should be an increase in ride height, in reverse, moving the lever backwards, should result in a decrease of the ride height. First thing to do after a repair is to remove all the air from the system. You should raise the car with the wheels hanging free and the engine running, move the lever fully in the ‘UP’ direction and let it sit for 5 to 10 minutes. You should repeat this perhaps 2 to 4 days. Driving also aids in the removing of the air. The air collects at the top of the shock absorber which then in turn is removed by the previous procedure on the car lift. The only way I can tell, in my opinion, that all the air is gone is by repeating the above procedure, It took 4 days before I felt the car was stable again in cornering and driving, and I did not have sudden changes in characteristics. After a few days you can adjust the ride height. The lever on the control valve has in the center ( ‘0’) position, vertical, a small dead zone in the ride height control between raising and lowering the rear. You should check the center position carefully. One should slowly move the lever a little in the direction to raise the rear and listen carefully for the sound of flowing hydraulic oil. Small movements of the lever cause large changes. The trick is to adjust the ride height (with the prerequisite extra weight in the trunk) exactly at the point where you can hear the hydraulic fluid flow. You probably will need a few tries to get this right but you try to get the ride height correct at the onset of the hydraulic fluid noise. Now carefully tighten the lever without moving it relative to the stabilizer bar. Now check the ride height once more without the weight in the trunk, it should not have changed Note: Theory and real world are two different entities and there is no sure method to remove the air. I removed the air 5 times on the same day and re-adjusted the ride height , then I would find the car the next morning sunk uneven again. the abnormal drive characteristics disappeared at the same time the pentosin level stabilized. Note: The car stood lower in the right, but the left side would also sink over night, as measured with a ruler. When the car started the rear would pump back up, but the pentosin level would be permanently a little lower unrelated to the control valve and the new bombs. Mainly the right side maintained a lot of air in the shock absorber. I have a special test corner and the car would go soft in the rear, something that never happened with the olf shock absorber. But luckily now the right shock is okay.

[StoyanG]

OK, so today I've changed the drive shaft bearing, and managed to make some photos, this in the red circle is the bleed valve as you showed me by the pictures. But as I've touched them on both sides it looks more lik there are rubber caps. I would like to be sure that those caps are not removed in order to do the bleeding procedure.

[shogun]

see post 35
http://www.7-forum.com/forum/24/komp...age-84467.html
and here is a cross section drawing under section 1.4.5 and it shows item 5 Verbindung Aussenluft
ftp://bmw-wiki.org/PDFs/SeminarArbei...ial_NR_EDC.pdf

[StoyanG]

As far as I saw on the drawing fro, the PDF, this is shown there as a bolt which could be unscrewed.
As for the explanations of the people - should i take a look on the link givven on post 35 ?

[shogun]

here is the pic from post 35, I uploaded it
http://imageshack.us/photo/my-images...htestelle.jpg/
Tat is the bleeding hole. Usually nothing to remove, just lift the rear of the car and let engine run and 'play' with the rgulating valve as described before.
I have seen people putting screws, rubber caps and what else in this hole as they thought it was leaking from there, but actually that is for bleeding.

[StoyanG]

So up to now on, I've lifted the car with the rear hanging freely and engine running - nothing comes out of those bleeding holes.
Playing with the regulator, while car is on the ground doesn't help either.
So you mean to put the car up with free hanging rear AND play with the regulator at the time, in order to get more pressure in the shocks and get the air out?

[shogun]

yes, exactly.
First thing to do after a repair is to remove all the air from the system. You should raise the car with the wheels hanging free and the engine running, move the lever fully in the ‘UP’ direction and let it sit for 5 to 10 minutes. You should repeat this perhaps 2 to 4 days. Driving also aids in the removing of the air. The air collects at the top of the shock absorber which then in turn is removed by the previous procedure on the car lift. The only way I can tell, in my opinion, that all the air is gone is by repeating the above procedure

[StoyanG]

So I did the things I've been told by Shogun, but still on the right side the car is higher.
No fluid didn't come out. At the moment the car is lower than previously.
Today before I got it lower, at the morning I was driving and at some point the rear end got quite stiffer than when I've started the car. And further more after some driving it seems to me that the lower left side gets higher than at the cold start.

[shogun]

could it be, that your regulating valve does not work or the hoses are plugged between regulating valve>>bombs>>shocks? Have you removed the hoses from the shocks and seen pressurized Pentosin coming out? Or mixed up the connection at the regulating valve? Feed and discharge?

It is a wild guess, but one never knows.

[StoyanG]

So two years later, while the car was sitting - the ride height it high again, the right shock absorber is hard as a rock, and the car is bouncing.
On the left side the ride is a lot softer and this difference causes the car to be unstable.
I'm planning a change of the bombs in a few days and give a feedback, what have changed etc.

Still I could not explain myself, why the right side is higher - maybe because the bomb on that side is a goner or something else?

[StoyanG]

A mod that I've come up with: I've changed the original seals of the shock absorber with new ones, made for hydraulic cylinders.
Z94fZ9.jpg

enVmJs.jpg

kokIc1.jpg

As you can see the original upper seal was removed, but not all of it, as there is a washed at the bottom of the seas, which could not be removed from the bed. Therefore only the rubber has been cleaned with a knife, and the new gasket was put in place, with a little bit of sealant (silicone).
The bellow part has been disassembled, and another new gasket (or whatever the english name of this is) has been put in place with a little sealant.
Sizes of the seals are 17x25mm, and as said - their application is high pressure hydraulic cylinders.
For the moment everything is running clean and dry.

[Sansouci]

Sound like the accumulator on the right side failed. Regrettably, when mine failed I replaced the system with a standard shock and coil spring setup. I wished I had fixed it.
--Ken

[StoyanG]

I'm sure one of the two bombs has failed, but since I've got a minor leak on the left side shock now, I'm planning on replacing the regulator + both bombs + fixing the leaking left shock.
I've recently fixed the right shock leak, since it was leaking badly.
More pics to come, and I still don't know how are we going to unscrew the hoses. Seems like mission impossible.

[shogun]

The hoses are usually crimped and the 'nuts' are unfortunately so corroded that it is difficult to get the hoses off with a normal wrench. Best is to take out the shock with bomb and hoses attached and put them into a vice and then use a large water pump wrench.

[NE32]

Hopping in this old thread for clarification. Replaced my accumulators and threw in lowering springs. The rear is sitting pretty high. I tried to bleed the system per Bentley instructions. My question is, how do I adjust it down now? I was able to use the lever to adjust the rear down before I replaced everything but now it does nothing. Do I need to reset anything at the regulating/control valve? I know you can set it to "zero" but I didn't touch it when I replaced everything. Or is there still air in the system and it'll go down when it works itself out?

[shogun]

Did you drive already a bit that everything is settling and maybe air comes out?

Usually it should come back to normal position. If you want to adjust the rear height, see my website under fixes>>>LAD>>>LAD adjustment.

The system is self bleeding. See filling and bleeding procedure on page 37-00/13 and adjust ride level height as per page 37-12/10
https://www.bmwtechinfo.com/repair/m...es/4810642.jpg
https://www.bmwtechinfo.com/repair/m...es/4810643.jpg

For bleeding the steering/servotronic pump you do not have to lift the car/4 wheels. For the LAD shocks you have to lift the rear so the shocks hang down, that will open a tiny bleeding hole at the shock botttom (the smaller part of the shock).

The ride height is adjusted to a predefined height (distance from the edge of the rim to the edge of the wheel well) with the pre-defined weight in the trunk. Both values can be found in the workshop manual + Bentley. From our own experience to make it faster: You should loosen the lever on the stabilizer so you can change the adjustment. If you move the lever forward, in the driving direction, you also move the lever on the control valve forward and the result should be an increase in ride height, in reverse, moving the lever backwards, should result in a decrease of the ride height. First thing to do after a repair is to remove all the air from the system. You should raise the car with the wheels hanging free and the engine running, move the lever fully in the ‘UP’ direction and let it sit for 5 to 10 minutes. You should repeat this perhaps 2 to 4 days, if absolutely necessary. Driving also aids in the removing of the air. The air collects at the top of the shock absorber which then in turn is removed by the previous procedure on the car lift.

The only way I can tell, in my opinion, that all the air is gone is by repeating the above procedure.

Adjusting the ride height. The lever on the control valve has in the center ( ‘0’) position, vertical, a small dead zone in the ride height control between raising and lowering the rear.
You should check the center position carefully. One should slowly move the lever a little in the direction to raise the rear and listen carefully for the sound of flowing hydraulic oil. Small movements of the lever cause large changes.

Bentley's has a table for LAD equipped cars as follows:
Wheels Rear ride height
15 in. 522 +/-3 mm (20.55 +/- 0.4 inches)
16 in. 529 +/-3 mm (20.93 +/- 0.1 inches)
17 in. 545 +/-3 mm (21.46 +/- 0.1 inches)

Ride height is measured from the lower edge of the wheel arch to the bottom edge of the wheel rim (not the ground).

[NE32]

Honestly, I've driven maybe 20 minutes since I've put everything back in. Haven't had time to really drive it. I'm gonna leave the rear wheels off the ground for a few days and drive it more next week. I'll report back.