6.9 suspension issues

[-bb-]

Having a weird issue with the suspension on my 6.9 which I am after some advice on.

Background:

Until recently, the front would sink overnight and the back would stay up. A replacement front levelling valve fixed that.

New issue:

Over the last couple of days a new issue has started where, while driving, the front will sink and the back will raise up at the same time. Here is a picture of how it ends up:

Putting the suspension on the high setting, letting it raise up (which both the front and back do immediately) and then back to the low setting puts the car back level. Then, some random time later, it does it all over again. The pressure light does not come on (i.e. the only warning is when the front starts to sink).

Any advice on what might be causing this would be most appreciated. My first thought is the front valve again, but before I follow that up, I am hoping there are simpler things I can check for.

 

[Styria]

Hi bb, the old bugbear ! Not good, is it ? Okay, as you know you demonstrated to one of your friends the height level facility (that's good), but it is my understanding that you did not push the disc back properly to the rolling pin, which constitutes the normal ride height position. When of course you then drive the car with the disc "in a no-man's position", the car will slowly lose height even when driving.

Forget the fact that it attains the high position, and then in turn, the low position without any difficulty. It seems quite clear to me that there is air in the system, thus preventing the hydraulics doing their job properly.

I would first of all bleed the system, and then start using the car more frequently. In any case, as you may have read by now, we have a get together on the Sunday, 5th or 6th June, so why not bring your car then for me to have a look at. There'll be no charge to you. Regards Styria

N.B. There may be other members with an opinion on this matter, and please feel free to join in. I don't know everything.

 

[Oversize]

It's possible that your front valve has been set just above the bleed down position & any slight variation in the road surface is causing it to drop into bleed down mode. It could also be caused by excessive wear in the components connected to the valve (eg valve link, stabilizer bar bushes), or something's loose. Of course it must be mentioned that I'm not an expert in removal / installation of a replacement valve, so my comments must be taken in context.... For example, I don't know how far you can vary the default ground clearance (normal mode) before bleed down (or pump up), is induced. I'm also not sure if worn upper (or lower) control arm bushes, or strut mounts would affect height control.

 

[Oversize]

I'd also suggest the rear valve is detecting that the vehicle is too low & subsequently pumping up the rear.

Of course it all could be caused by the speed sensitive "pounce sensor" which places the car into "attack mode"......

 

[CraigS]

I would disconnect the cable from the main valve and put it into the low (normal) position, then drive it for several days like that and see if it remains stable. It may just be that the inner cable needs to be lubed and adjusted. Common problem with the inner cable as they are just not used frequently.

 

[Oversize]

Have a read of the manual in the attached link & this may assist you to diagnose the problem...

http://handbook.w116.org/Chassis/32-555.pdf

 

[Oversize]

Other topics that may also help:

http://handbook.w116.org/Chassis/32-560.pdf

http://handbook.w116.org/Chassis/32-515.pdf

Note that I haven't had the time to read these myself.....

 

[Styria]

Hi Mark, I never look at the library on that site, so I decided to check out your referrals. So far, I have found that the pages do either not open, or seem to take an inordinantly long time to do so, with the result that I simply lost patience. Besides, in the very near future our Technical Section will have a complete run-down from a genuine Workshop Manual, but I am still in the throes of finding the means of transferring the scanned pages (64 of them) into some form of PDS format - at the moment, I am investigating this procedure with PDF Creator and Soda PDF. Anyone like to add to that ? Please ?

Getting back to bb's problems, such as they are, and utilizing Technical information contained within a workshop manual. The checking and testing procedure is complex, and certain tools and gauges are required for testing purposes and, additionally, certain procedures need to be followed in order to track a problem. This will all be explained and become obvious once the PDF document becomes available on our website. Regards Styria

 

[Michel]

I would disconnect the cable from the main valve and put it into the low (normal) position, then drive it for several days like that and see if it remains stable. It may just be that the inner cable needs to be lubed and adjusted. Common problem with the inner cable as they are just not used frequently.

I agree with Craig on this one.

However, the biggest enemy of the 6.9 suspension is the lack of use...

 

[Oversize]

I'm not sure why my links don't work, but if you go into the site manually, you'll have more luck.... It's the only site I've seen so far that has comprehensive manuals available without having to join a club (or be a dealer).

 

[WGB]

Copies of that US W116 electronic manual are often available off ebay for a few dollars only.


Styria - I have a fully licenced version of Adobe Acrobat 9 and would be happy to make it into a document if you wanted to mail me a disc or a thumb drive with the data on it.

I produced a fully indexed M-100 engine manual (using the original TIFF version with the blurry pictures in negative commercially available copies of the microfiche files) and forwared it to an FTP site in teh US and it was all supposed to go on the M-100 site but it never seemed to get past theguy I sent it to.

Bill

 

[Styria]

Copies of that US W116 electronic manual are often available off ebay for a few dollars only.


Styria - I have a fully licenced version of Adobe Acrobat 9 and would be happy to make it into a document if you wanted to mail me a disc or a thumb drive with the data on it.

I produced a fully indexed M-100 engine manual (using the original TIFF version with the blurry pictures in negative commercially available copies of the microfiche files) and forwared it to an FTP site in teh US and it was all supposed to go on the M-100 site but it never seemed to get past theguy I sent it to.

Bill

Hi Bill, thanks for your most kind offer. Honestly, I really need to get my head around all this - I have had help from Michel and abl567 and I am still working on some possible options, and still trying to overcome a number of confusing aspects. I have lots of info and other documentation, and tests etc. etc., and I will be in touch with you soon. Thank you again. Regards Styria

 

[Oversize]

I always thought that by jacking up a 6.9 with the suspension in the normal position, the system would be completely depressurized and thereby safe for repairs. But it seems many are suggesting the cable should be disconnected and the disc on the main valve repositioned. Why?? And what happens if this step isn't followed....

 

[WGB]

I had a salutory lession when I dismantled my suspension over xmas.

I have always found that simply raising the car on the hoist depressurises the system but this time it remained with some residual pressure which showed itself as a liberal shower of lubricating oil while undoing the first connection.

I tightened it up again and moved the disc to the "M" position and with a very audible hiss it depressurised itself properly.

Bill

 

[Tony66_au]

Lucky it wasn't hot Bill!

 

[Styria]

Nowadays, whenever I attend to any suspension issues, and no matter what position the disc is in (even Maintenance), I expect a fair bit of hudraulic pressure coming from just about any fitting I might undo. Consequently, a large dish plus a rag are the order of the day. I just undo the fittings a little, and give them time to purge themselves. It only takes about a minute most times. Regards Styria