CL55 ABC gets stiff after bump
02-10-2016, 09:43 PM
#1
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2002 Mercedes-Benz CL55 AMG
CL55 ABC gets stiff after bump
Rather cryptic title, here is more detail:
2002 CL55
Driving at freeway speeds, I'll hit a sharp bump on the road, it's always the transition between the road and an overpass. I can't quite tell yet if the suspension is maxing out or maxing compression. But I'll feel a noticeable 'clunk' in the LH rear strut. After this happens my suspension maxes out, goes rock solid, the car raises to max ride height. I have to stop the car and turn off the engine, and when I restart the car settles back to normal.
My gut says that my ABC pressure is borderline low, maybe the pump is marginal at 187,000 miles, when I hit a sharp bump it makes the pressure drop just enough to trigger the 'fail-safe' mode.
No white or red ABC warning. Except one time when it did this, I could swear I got the red warning for a split second as it happened. By the time by eye looked down it was gone. But that can't be, right, because if a white or red warning came on it would stay on, correct?
I understand that this is a self-protection measure if the car loses ABC pressure, correct? In which case if the strut (or both rear struts?) were max extended, could the ABC pressure drop low enough to trigger the 'locking' of the suspension in full-extended mode?
Is it correct to say that the ABC system in normal mode is compressing the springs in the struts, and if there was an abnormal loss in pressure the struts would mechanically extend to max extension? That seems a good way to design the system as fail-safe. I might be all wet, just a layman's guess.
Anyway I know exactly these spots on the road in my daily drives lol. I avoid them at all costs. Slowing way down to say 30 mph prevents the issue over a 'known' bump in the road. Still it's very frustrating and I'd like to solve it.
What do you guys think?
2002 CL55
Driving at freeway speeds, I'll hit a sharp bump on the road, it's always the transition between the road and an overpass. I can't quite tell yet if the suspension is maxing out or maxing compression. But I'll feel a noticeable 'clunk' in the LH rear strut. After this happens my suspension maxes out, goes rock solid, the car raises to max ride height. I have to stop the car and turn off the engine, and when I restart the car settles back to normal.
My gut says that my ABC pressure is borderline low, maybe the pump is marginal at 187,000 miles, when I hit a sharp bump it makes the pressure drop just enough to trigger the 'fail-safe' mode.
No white or red ABC warning. Except one time when it did this, I could swear I got the red warning for a split second as it happened. By the time by eye looked down it was gone. But that can't be, right, because if a white or red warning came on it would stay on, correct?
I understand that this is a self-protection measure if the car loses ABC pressure, correct? In which case if the strut (or both rear struts?) were max extended, could the ABC pressure drop low enough to trigger the 'locking' of the suspension in full-extended mode?
Is it correct to say that the ABC system in normal mode is compressing the springs in the struts, and if there was an abnormal loss in pressure the struts would mechanically extend to max extension? That seems a good way to design the system as fail-safe. I might be all wet, just a layman's guess.
Anyway I know exactly these spots on the road in my daily drives lol. I avoid them at all costs. Slowing way down to say 30 mph prevents the issue over a 'known' bump in the road. Still it's very frustrating and I'd like to solve it.
What do you guys think?
02-11-2016, 09:11 AM
#3
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2002 Mercedes-Benz CL55 AMG
Incredibly useful site, every ABC owner needs to print this off and place it on top of the toilet for daily reference:
http://mercedes-abc-drive-carefully.blogspot.co.uk/
My issue?
- Going stiff over bumps = accumulators.
- Annoying whine I've had for a while that I had let drift into the back ground noise? Pulsation damper.
- Settling to the RH rear corner when parked? Bad valve in rear valve block. I know about this issue when I had the valve block rebuilt, great mechanic helped me on that. I decied to go cheap and try it, it works fine just settles when off. At some point I'll need a new rear valve block.
I really need to buy a STAR, I understand those pop up on eBay from time to time for about $800 with cables. I'll need to keep an eye out.
http://mercedes-abc-drive-carefully.blogspot.co.uk/
My issue?
- Going stiff over bumps = accumulators.
- Annoying whine I've had for a while that I had let drift into the back ground noise? Pulsation damper.
- Settling to the RH rear corner when parked? Bad valve in rear valve block. I know about this issue when I had the valve block rebuilt, great mechanic helped me on that. I decied to go cheap and try it, it works fine just settles when off. At some point I'll need a new rear valve block.
I really need to buy a STAR, I understand those pop up on eBay from time to time for about $800 with cables. I'll need to keep an eye out.
02-11-2016, 10:19 AM
#4
great site! thanks.
