Intermediate Height Question

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Fumbler
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Intermediate Height Question

Post by Fumbler »

Since being fixed, the car raises and lowers to the proper height on every setting, apart from intermediate height. When I select this with the lever, only the front raises, and the rear does nothing at all- it just stays at standard ride height.

What's going on? Is there slop in the rear linkage (after all, it has done 106000 miles) which is causing a lack of necessary movement in the rear height corrector, or is the rear height corrector getting gummed up inside?

Interested to know you people's thoughts on this. Fortunately, the car functions fine apart from this little niggle.

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Re: Intermediate Height Question

Post by rutter123 »

Rear height corrector or linkage I suspect.
Have you tried bouncing the rear to get it to correct itself?
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Re: Intermediate Height Question

Post by Fumbler »

rutter123 wrote:
Mon Aug 28, 2023 3:56 pm
Rear height corrector or linkage I suspect.
Have you tried bouncing the rear to get it to correct itself?
Yes- I sit on the rear end, and the rear end self levels. When I get off, it raises up and then lowers down, however it still maintains normal ride height, even when the lever is set to intermediate.

It's leading me to believe there's just enough play in the linkage whereby it works on the extremes and on normal height, but not fine enough anymore to make the rear respond. When it's on the lift next week I'll ask if they think putting nylon collars on or something to take up the slack may help.

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Re: Intermediate Height Question

Post by rutter123 »

I believe there is a plastic linkage somewhere on the control rod on the underside which wears (don't quote me on this it's been a long time since I looked) and yes you're right any slack will affect the full movement of the h/c moreso the rear.
Rear h/c arm can seize over time, if you have access to a ramp it maybe worth disconnecting the linkage at the h/c and trying to move it manually to see what results you get.
I would assume your LHM tank has enough fluid.
Give the h/c a good soak with decent penetrating oil the day before.
Rebuild kits are available from Pleaides so are re-con height correctors.
I'm fairly sure there is an amount of "adjustment" on one of the linkages or it could just be a worn pivot.
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Re: Intermediate Height Question

Post by Fumbler »

rutter123 wrote:
Thu Jan 27, 2022 11:13 am
I believe there is a plastic linkage somewhere on the control rod on the underside which wears (don't quote me on this it's been a long time since I looked) and yes you're right any slack will affect the full movement of the h/c moreso the rear.
Rear h/c arm can seize over time, if you have access to a ramp it maybe worth disconnecting the linkage at the h/c and trying to move it manually to see what results you get.
I would assume your LHM tank has enough fluid.
Give the h/c a good soak with decent penetrating oil the day before.
Rebuild kits are available from Pleaides so are re-con height correctors.
I'm fairly sure there is an amount of "adjustment" on one of the linkages or it could just be a worn pivot.
I imagine it's a worn pivot- Chevronics have verified that the H/C works as it should, and all the linkages are free, moving and have been lubricated. At another garage I was fiddling with rear height adjustment collar on the ARB and it moved accordingly. The LHM tank is full. It's going back to Chevronics next week so I'll ask them to investigate and see what they say. It'd be nice to have it working properly again.

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Re: Intermediate Height Question

Post by white exec »

Tiny adjustments of the collar on the ARB can produce quite large height changes. The angular movement of the ARB is quite small.
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Re: Intermediate Height Question

Post by Fumbler »

white exec wrote:
Thu Jan 27, 2022 11:45 am
Tiny adjustments of the collar on the ARB can produce quite large height changes. The angular movement of the ARB is quite small.
That makes sense.I'll see what the techs say.

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Re: Intermediate Height Question

Post by thorter »

On each axle, the normal height is set by the height corrector control loop alone. The height lever linkage has a central dead (clearance) zone, and does not connect with the control loop. To get the intermediate height, the height lever now moves past the dead zone and contacts the height corrector to add a bias which offsets the position. Finally, at the fully up and fully down positions, the height lever linkage forces the height corrector to one or other end position, overriding the actual vehicle height.

It is indeed likely that your problem is due to wear and slop in the linkages, and if so, fixing that would be good. Do make sure you do not adjust the normal height which seems to be correct, unless you are very sure someone has tampered with it. You may be able to adjust the height lever linkage at the rear height corrector. I have forgotten the details of exactly how this is done, but you should be able to recognise the features described. I vaguely remember there is a threaded rod with back to back nuts, and that this is the adjustment you want, the gap between the points contacting the height corrector determines the dead zone. Best of luck.

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Re: Intermediate Height Question

Post by Fumbler »

thorter wrote:
Thu Jan 27, 2022 3:27 pm
On each axle, the normal height is set by the height corrector control loop alone. The height lever linkage has a central dead (clearance) zone, and does not connect with the control loop. To get the intermediate height, the height lever now moves past the dead zone and contacts the height corrector to add a bias which offsets the position. Finally, at the fully up and fully down positions, the height lever linkage forces the height corrector to one or other end position, overriding the actual vehicle height.

It is indeed likely that your problem is due to wear and slop in the linkages, and if so, fixing that would be good. Do make sure you do not adjust the normal height which seems to be correct, unless you are very sure someone has tampered with it. You may be able to adjust the height lever linkage at the rear height corrector. I have forgotten the details of exactly how this is done, but you should be able to recognise the features described. I vaguely remember there is a threaded rod with back to back nuts, and that this is the adjustment you want, the gap between the points contacting the height corrector determines the dead zone. Best of luck.
Thanks for this- you've helped me understand how the system works a lot better now! To clarify, the ride height was adjusted by Chevronics while they were fixing a front linkage failure. I don't intend on tampering with that myself. I'm going back up to them next week as a follow-up to their work, so I'll point out the issue (now that I have a better understanding) and what I think is causing this. They should be able to get it fixed up.

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Re: Intermediate Height Question

Post by thorter »

Please ignore the bit about adjustment by two nuts. It must refer to an earlier model than the BX. I found a Haynes manual for the BX. There is not much info, but it looks like you set the manual control by moving the pivot of a lever (that couples and reverses the direction of the manual control) to centre the control rod in a window. But the principle is the same, the window provides the dead zone.

Assuming nothing else is wrong, and if setting it like that does not then give the correct intermediate height, I would just move it slightly in the appropriate direction till the height is correct.

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Re: Intermediate Height Question

Post by Fumbler »

thorter wrote:
Thu Jan 27, 2022 9:16 pm
Please ignore the bit about adjustment by two nuts. It must refer to an earlier model than the BX. I found a Haynes manual for the BX. There is not much info, but it looks like you set the manual control by moving the pivot of a lever (that couples and reverses the direction of the manual control) to centre the control rod in a window. But the principle is the same, the window provides the dead zone.

Assuming nothing else is wrong, and if setting it like that does not then give the correct intermediate height, I would just move it slightly in the appropriate direction till the height is correct.
Which is probably what's going to happen, unless the rod can be shimmed with a plastic sleeve or something to regain the appropriate bias the intermediate height setting should provide.

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Re: Intermediate Height Question

Post by Jaba »

First thing to check is the clearance gap of the long rear height corrector linkage where it engages with the pivot gate, as mentioned above, for the rear HC. As this would give the symptoms you have. Details are in Haynes, I forget the exact distance it should be. Also lubricate that pivot, its essentially a nut and bolt and it does get stiff due to rust.
The plastic bush that wears is up by the height correctors and links the adjustment device rods on the roll bars to the HC. I dont think a bit of wear here is critical.
There is very little difference in adjustment terms between normal and intermediate height unlike between the max and minimum heights, so any setup adjustment fault will show up there.
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Re: Intermediate Height Question

Post by Fumbler »

Issue was resolved by replacing a worn bronze bush in the rear height corrector lonkage. Everything on the suspension is now mechanically sound. The first it's been for a long time.