ABC Suspension Fault Diagnosis

[MercedesMutant]

Hi Guys,

I was wondering if anyone could help me find diagnose this problem.

I have a groaning coming from my OSR suspension when driving, sort of like a rumbling/bouncing but it's not a wheel bearing type noise, it's definitely related to compression and rebound in the suspension.

Could be ABC fault? No errors on ABC, no temporary flashing of ABC fault on bumps, no sagging and vehicle raises and lowers as expected, the CHF11S fluid was changed about 20k miles ago.

The tyre in question has cupping wear pattern, like you'd get with a blown shock absorber on a car with traditional suspension.

My thoughts are:

ABC strut failure? Accumulator failure. The rear subframe bush may have some play, could this be causing the issue, I need to investigate that further.

Thanks,
Jim.

 

[Binnedit]

Hi Jim

If you haven't got an ABC warning light on, I would ask a friendly techy to lift it up on a ramp, get a pry bar in there & give everything a damn good wiggle, in the first instance.

Worn bush replacement is likely to be far cheaper that many ABC repairs

 

[Blobcat]

I’d be looking for a bush issue as well…

 

[Mark Q]

Could be ball joint, that appears to be a commonish issue.

 

[MercedesMutant]

It's leaking now, I aren't sure if it's the ABC Fluid or the the traditional part of the shock that's leaking but it's VERY wet and oily.

ABC Fluid isn't going down and the fluid is orangey black not green, so I think it's the traditional bottom half of the shock that's blown?

So probably needs a new pair of rear struts which is a ball ache.

 

[Craiglxviii]

It's leaking now, I aren't sure if it's the ABC Fluid or the the traditional part of the shock that's leaking but it's VERY wet and oily.

ABC Fluid isn't going down and the fluid is orangey black not green, so I think it's the traditional bottom half of the shock that's blown?

So probably needs a new pair of rear struts which is a ball ache.

There isn’t a “traditional” part; there’s a spring mounted inside a strut with a hydraulic actuator on top. The only thing that can leak is the piston.

 

[MercedesMutant]

There isn’t a “traditional” part; there’s a spring mounted inside a strut with a hydraulic actuator on top. The only thing that can leak is the piston.

I was under the impression that the ABC dealt with below 5hz frequency of damping and the traditional shock inside the strut handled above? It's a spring and dampers with a hydraulic ram on top that can deal with body roll and low frequencies.. At least that was my understanding? I could be wrong though?

 

[Craiglxviii]

I was under the impression that the ABC dealt with below 5hz frequency of damping and the traditional shock inside the strut handled above? It's a spring and dampers with a hydraulic ram on top that can deal with body roll and low frequencies.. At least that was my understanding? I could be wrong though?

Yes, and no, the spring takes the shock and the hydraulics provides the damping.

The good news for you is that new struts for your 215 are c.£300 each from AliExpress.

There’s no way to rebuild struts from a 215; been there, done that (to the point of having the ram stripped and rechromed…)

 

[MercedesMutant]

1 Head bearing
· 2 Hydraulic line
· 3 Steel spring
· 4 Stop buffer
· 5 Bottom valve
· 6 Shock absorber
· 7 Piston rod
· 8 Boot

 

[Craiglxviii]

1 Head bearing
· 2 Hydraulic line
· 3 Steel spring
· 4 Stop buffer
· 5 Bottom valve
· 6 Shock absorber
· 7 Piston rod
· 8 Boot

View attachment 80563

Hydraulics, springs…

 

[alexanderfoti]

There is a damper inside the strut, and it does sound like yours has failed.

 

[MercedesMutant]

There is a damper inside the strut, and it does sound like yours has failed.

Thanks @alexanderfoti for confirming, it definitely seems that way as the fluid is not leaking around the connection or the top of the strut it's leaking up the shaft and down the side of the strut which I believe is the lower section shock (no 6 on the diagram) that's unfortunately blown, the right rear strut also sounds like it could be knocking slightly (top hat failure?) hard to tell i'll need two people and have to take out the rear parcel shelf to see the top mount with someone else moving the suspension.

So I think i'm looking at two new rear ABC struts, depending on the prices I can find them for this maybe a coil over conversion, albeit I'm going to try save the ABC system if I can afford to do so as I think the benefits are worth it, the handling is pretty spectacular for a 2 tonne land yacht.

 

[LostKiwi]

AliExpress do reasonably priced ABC units that have been used successfully by some on here.

 

[MercedesMutant]

Had time to get the car in the air and get a pry bar on all the suspension and subframe location points, nothing loose or knocking.
Right rear shock appears to be fine, i've cleaned it all up with brake cleaner and i'll keep an eye on that shock.

The left rear shock has blown (the traditional bottom section) so the knocking/bouncing is most likely the tyre/wheel bouncing and perhaps even the ABC system trying to compensate for it?

All the control arms on the right hand rear side of the vehicle look brand new so someones been trying to fix that groaning noise, but I suspect it's one of those things that plays a trick on the ear (when in the car) and it's the left hand side it's coming from with the blown shock.

I'll source a new left rear ABC strut and replace myself, then most likely get a wheel alignment also as It needs it, hopefully if I get one for a decent price I can save myself quite the sum of money.

 

[Craiglxviii]

Thanks @alexanderfoti for confirming, it definitely seems that way as the fluid is not leaking around the connection or the top of the strut it's leaking up the shaft and down the side of the strut which I believe is the lower section shock (no 6 on the diagram) that's unfortunately blown, the right rear strut also sounds like it could be knocking slightly (top hat failure?) hard to tell i'll need two people and have to take out the rear parcel shelf to see the top mount with someone else moving the suspension.

So I think i'm looking at two new rear ABC struts, depending on the prices I can find them for this maybe a coil over conversion, albeit I'm going to try save the ABC system if I can afford to do so as I think the benefits are worth it, the handling is pretty spectacular for a 2 tonne land yacht.

The ABC struts for 215 are £300 on AliExpress.

 

[ajlsl600]

Hi Guys,

I was wondering if anyone could help me find diagnose this problem.

I have a groaning coming from my OSR suspension when driving, sort of like a rumbling/bouncing but it's not a wheel bearing type noise, it's definitely related to compression and rebound in the suspension.

Could be ABC fault? No errors on ABC, no temporary flashing of ABC fault on bumps, no sagging and vehicle raises and lowers as expected, the CHF11S fluid was changed about 20k miles ago.

The tyre in question has cupping wear pattern, like you'd get with a blown shock absorber on a car with traditional suspension.

My thoughts are:

ABC strut failure? Accumulator failure. The rear subframe bush may have some play, could this be causing the issue, I need to investigate that further.

Thanks,
Jim.

Bottom ball joint on strutt?

 

[MercedesMutant]

Bottom ball joint on strutt?

Since the strut is being replaced, I think it's irrelevant at this point. I'll do the left rear first and see if that resolves the problem and perhaps follow up with the right rear if it needs it.

 

[alexanderfoti]

Bottom ball joint on strutt?

The rears have a bush rather than a ball joint.

 

[MercedesMutant]

The rears have a bush rather than a ball joint.

I know I just had a pry bar in there I just didn't want to say anything.

 

[ajlsl600]

The rears have a bush rather than a ball joint.

OK stand corrected.