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Thread: Touring SLS-testing ?

  1. #1
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    Touring SLS-testing ?

    Guys

    I have recently bought a '93 525 touring very cheaply as my daily runner. Being a UK car, it has self levelling rear suspension.
    Having previously had a saloon, I don't know what the SLS is supposed to "feel" like, but in an unladen state the rear feels incredibly hard over bumps. Fluid level is fine and correct fluid in there.

    Question-is there an obvious way to test the system to be sure I don't have a fault?

    Many thanks.
    Kind regards

    John

    1993 BMW E34 525i SE Touring
    1989 BMW E30 320i SE Touring
    1986 Porsche 944 Lux
    1982 Porsche 924 Lux
    1979 Porsche 924 Lux

  2. #2
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    The factory manual specifies a ride height with the car laden down - that would be one test. However, I don't think that would detect if you have blown pressure accumulators, which would cause a very hard ride.

    I just replaced my rear SLS shocks and I can assure you the ride should not be hard over bumps - it should ride like a normal car when it's unladen. A very hard ride normally indicates that your pressure accumulators are shot and need to be replaced. Other than that, look for leaks in the hydraulic system back there.

  3. #3
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    Throw some weight in it and see if the rear ride hieght is maintained.

  4. #4
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    Quote Originally Posted by eddycooper View Post
    The factory manual specifies a ride height with the car laden down - that would be one test. However, I don't think that would detect if you have blown pressure accumulators, which would cause a very hard ride.

    I just replaced my rear SLS shocks and I can assure you the ride should not be hard over bumps - it should ride like a normal car when it's unladen. A very hard ride normally indicates that your pressure accumulators are shot and need to be replaced. Other than that, look for leaks in the hydraulic system back there.
    Thanks for that. I can't see any leaks and I was wondering if there were any specific tests to confirm accumulator faults? A new pair are £400 so I want to be certain!!
    Kind regards

    John

    1993 BMW E34 525i SE Touring
    1989 BMW E30 320i SE Touring
    1986 Porsche 944 Lux
    1982 Porsche 924 Lux
    1979 Porsche 924 Lux

  5. #5
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    If your accumulators are blown the rear will sag overnight. Measure the rear ride height right after you shut the engine off for the night. Measure it again the next morning before you start the car. If it's sagged overnight and your ride is hard it's safe to say they're blown and need replacing.
    Cosmos Black/Black 1995 540iA M-Sport
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  6. #6
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    If the sls is dead you can always delete it and install regular rear shocks. Not as nice a ride as sls but way cheaper.

  7. #7
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    Thanks guys-this is all very helpful. Will try the measuring thing tomorrow.
    Been looking and it seems that I can get a pair of new accumulators for about £200, so if it needs them.......
    Kind regards

    John

    1993 BMW E34 525i SE Touring
    1989 BMW E30 320i SE Touring
    1986 Porsche 944 Lux
    1982 Porsche 924 Lux
    1979 Porsche 924 Lux

  8. #8
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    As shapeshifter said. Put some weight in and see what happens. Should lift up. A simple adjustment and/or bleeding may be all that fixes it. Shogun has a bunch of info on sls or lad as he calls it.

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  9. #9
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    Quote Originally Posted by bubba966 View Post
    If your accumulators are blown the rear will sag overnight.
    I would have thought that this symptom would indicate a bad level control valve, not bad accumulators.


    If the accumulators are shot, their nitrogen charge leak out and work itself through the system and be automatically bled out, leaving nothing but hydraulic oil inside. With only hydraulic oil in the accumulators, they provide no cushion, and are therefore very hard. However, the level control function should still work fine. If only your accumulators are bad, I would expect to experience a very hard ride, but no effect on the ride height.

    As you found, the accumulators are not all that expensive. When you replace them you'll also need a couple litres of hydraulic oil - you'll lose a bunch during this exercise.

  10. #10
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    Quote Originally Posted by eddycooper View Post
    I would have thought that this symptom would indicate a bad level control valve, not bad accumulators.


    If the accumulators are shot, their nitrogen charge leak out and work itself through the system and be automatically bled out, leaving nothing but hydraulic oil inside. With only hydraulic oil in the accumulators, they provide no cushion, and are therefore very hard. However, the level control function should still work fine. If only your accumulators are bad, I would expect to experience a very hard ride, but no effect on the ride height.

    As you found, the accumulators are not all that expensive. When you replace them you'll also need a couple litres of hydraulic oil - you'll lose a bunch during this exercise.

    good explanation. In my M5, I had sagging rear and hard ride and a leaky rear shock. Park the car for a week or so and I had a puddle of yellow gold (Pentosin chf 7.1) under the reservoir where the sagging rear shocks would push the fluid back into the holding tank. One valve, 2 bombs, likely 2 shocks...$$$ ouch, SLS DELETE! $5 over the counter brake line and done/

  11. #11
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    Quote Originally Posted by eddycooper View Post
    I would have thought that this symptom would indicate a bad level control valve, not bad accumulators.


    If the accumulators are shot, their nitrogen charge leak out and work itself through the system and be automatically bled out, leaving nothing but hydraulic oil inside. With only hydraulic oil in the accumulators, they provide no cushion, and are therefore very hard. However, the level control function should still work fine. If only your accumulators are bad, I would expect to experience a very hard ride, but no effect on the ride height.
    The level control only functions when the engine is running. When it's shut off the weight of the car will slowly push the fluid out of the accumulators (which are only full of fluid because they're dead) causing the rear end to sag. Which is why I said measure the ride height at night when you shut off the car for the day, then again the next morning before you start it up. It takes a bit of time not running for it to sag enough to be noticeable. When it's running the ride height will be fine.

    I need to replace them in my M-Sport. Nothing is leaking so it's been a low priority. But when you start up the car in the morning I can feel the rear end raise up to proper ride height upon initial start up. And yeah, the rear end is riding rather hard. Next big sum of $ going into the M-Sport is going to be new accumulators & rear shock soft parts (mounts, spring pads, bump stops, dust boots, etc).
    Cosmos Black/Black 1995 540iA M-Sport
    BMW Individual Exclusive Edition, 1 of 65 total, 9/25/95 Build
    OEM additions include Euro trim, passenger seat mounted first aid kit, tool kit warning triangle, clears all around, black chrome exhaust tips, spare tire well gas can, and rear armrest fridge.

    Waiting for install is an adjustable lumbar support, & drivers side glove box...

  12. #12
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    You can easily confirm when the bombs are blown. Take the rubber hose off and poke a slim screwdriver inside. Don't use any force, you'll be poking against the rubber diaphragm if its still there. 9 times out of 10, the screwdriver will go all the way back because there is no diaphragm left. These are obviously bad. However, if the rubber is present it doesn't necessarily mean that you still have the right pressure left inside. They can still be bad.

  13. #13
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    Don't drive it on blown bombs either, you'll kill the regulating valve in a hurry. Ask me how I know.

  14. #14
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    Hey guys
    what makes the car gets high to the max and hard like a rock?
    where should i start the diagnosis of my SLS e34 m5 1992.
    every thing was working well suddenly the car is very high to the maximum .any idea
    regards

  15. #15
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    what have you checked so far? did you do any of what is in this thread?
    Steve

  16. #16
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    Wrong adjustment of the regulating valve or the 2 bolts which hold the regulating valve arm are lose and the regulating valve is not correctly set now.
    Shogun tricks and tips for the E32 series are HERE!

  17. #17
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    hi
    I just installed the SLS system on my E34 (just rear suspension).
    my problem is a bad noise coming from regulating valve.

    I've seen in M5 board someone saide that by largening the hole in banjo bolt and ... the problem will be solved but someone else did that with no effect on noise.
    anyone had experience?
    isn't that necessary to bleed the shocks before installing?
    because the shocks are upper than the bleeding valve in fluid circulation.

  18. #18
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    I have never heard, that people enlarge the holes of the banjo bolts, not necessary. Probably the valve is not set in zero position. No need to bleed shocks before installing, at the bottom of the shock is a bleeding hole and air goes out when the rear of the car is lifted and the wheel are hanging.
    LAD bleeding + correct adjustment information (see also my website)
    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, if required. 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
    Shogun tricks and tips for the E32 series are HERE!

  19. #19
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    Thanks for guides shogun

    this is where I've read about enlarging the orifices in banjo bolts and pipe...

    https://www.m5board.com/vbulletin/e3...oise.html?amp=

    but what I've actually done was as follow.

    - replace the wire reinforced hose coming from pump to adjusting valve by non wire reinforce hose (a little bit thicker)
    - enlarg the orifice on the banjo bolt and also the one at the end of relevant pipe from 1mm to 2mm (not 3mm that was proposed).
    - delet the orifice in the middle of the hose.

    believe or not the noise is totally gone and everything are working properly.
    Good to know that the reason I've installed a wire reinforced hose was that the old OEM hose that I've purchased together with the rest of the SLS system were used (just the accumulators are brand new) and during manual level adjusting the mentioned hose blown. unfortunately I was not aware that the blown old OEM hose was non wire reinforce!

    Conclusions:
    - using non wire reinforced hose is a must in car hydraulic system!
    - I still can't understand how a wire Armoured hose can make such a noise in system and specially in valve???
    - maybe without enlarging the two orifices and not deleting the third, annoying noise could be disappeared.

    20190420_203440.jpg20190414_200812.jpg20190505_144324.jpg20190425_144506.jpg
    Last edited by shervin; 05-05-2019 at 08:10 AM.

  20. #20
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    Congrats solving that problem. Maybe that is a special E34 M5 problem, never have experienced such a problem on E32 and I also cannot remember on E34 non-M5.
    Anyway, good to know and thanks for the pics. Can't remember to see such a orifice in the middle of the hose on my E32 750iL.
    1mm looks indeed very small for the banjo bolt orifice. Will check on my E32 next time I work on that too. Based on the drawings there is no orifice in the tube on my E32 http://bmwfans.info/parts-catalog/E3..._tubing_front/
    and the banjo bolt is p/n 32411140945 , same used on E34, also +M5 S38 and M5 3.6 S38.
    Maybe they had to install on the M5 a flow reducer for the SLS, as the engine RPM is much higher on the M5 compared to the normal engine, = more RPM for the power steering pump and more flow. This is the piping for the M5, and that looks different than on the E32, and there I can see the flow reducer for the M5 http://bmwfans.info/parts-catalog/E3...ont#1140945_11
    here in the middle of the hose it is fixed https://www.ecstuning.com/b-genuine-...g/37132226494/
    That does not exist on the E32 feed hose
    Last edited by shogun; 05-05-2019 at 07:52 AM.
    Shogun tricks and tips for the E32 series are HERE!

  21. #21
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    Yes there are orifices in the middle of OEM hoses going out (high pressure) from steering pump to steering box and SLS adj valve. Something like a large bullet with a small hole in the middle that are clamped from outside to avoid moving.

    steering hose.jpg
    Attached Images Attached Images
    Last edited by shervin; 05-05-2019 at 08:21 AM.

  22. #22
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    The banjo bolt with 1mm orifice you can see in picture posted before comes from an e34 525 Tds steering pump (SLS) and the one I've enlarged cames from a M5. both were exactly the same.
    But we know the Tds (have very slow moving engines (Turbo Diesel).
    I think we should search more to find out the reason of using these small orifices
    Last edited by shervin; 05-05-2019 at 08:37 AM.

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