LAD line vibration - Why?

[Von Bimmer Head]

I have a 1990 750iL that suffers from LAD line vibration. These are the lines that run to the rear of the car. The vibration/noise only happens after the pentosin oil becomes hot (10 min) and then only at low engine RPM. Accelerate and it goes away. the LAD system works fine. Seems like the valve is going unstable in the back. I adjusted the height and this did not help. Anyone had this problem before?

[libertylover]

Assuming that all of the clamps are all in place and that the other system components are secure, I'd try to bleed the system thinking maybe there's air trapped in there. Here's the procedure from the Bentley's manual:

-With engine off, fill LAD reservoir until fluid level is approximately 25 mm (1 inch) below the reservoir rim.

-Load car with 150 kg (332 lbs.) placed in the luggage compartment.

-Start engine. Turn steering wheel from lock to lock three times. Turn engine off.

- Raise rear of car until drive wheels are off ground. Wait about two minutes and check fluid level. Fluid level should be no more than 25mm (1 Inch) above the base of the reservoir screen. Correct fluid level as necessary.

It doesn't say but you'll probably want to remove the 332 lbs. of junk from the trunk hehe.

[Von Bimmer Head]

Thanks for the input. I have flushed the LAD circuit with new oil - no change. It is really a simple circuit but it is also hard to get to some of the components and difficult to put a pressure gage on. My feeling is that the valve is going unstable and causing pressure spikes???

Just thought I would ask the public before digging in. Anone known to be an expert at LAD?

[libertylover]

You said you flushed the system but before you spend money on a new valve you probably should do the bit about the 332 lbs. in the trunk if you didn't already. Remember, the purpose of the system is to automatically adjust to changing loads.

Another good forum is www.roadfly.org . I suggest you search the appropriate archive or post your problem there.

If it makes you feel any better, my system is leaking (more like seeping right now) and I'll have to fix it before long. Mine appears to be oozing fluid from somewhere near the pump.