6.9 front suspension not raising

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chrisp

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Hello everyone,

For those of you not familiar with my personal circumstances I have recently relocated from Sydney to Perth and in doing so have had to get my 6.9 inspected for roadworthiness and reregistered. It turned out I had a small leak from both my front levelling valve and the pump so these were duly replaced and I'm pleased to say the car passed inspection with flying colours.

However, the front suspension has been sinking overnight and much like MercedesMike's description of his car in another thread, is now failing to raise at all when the car is started. (The back stays aloft for weeks and all five spheres were replaced by Styria recently, prior to moving across.)

During the phase that the front would raise it seemed to be riding low for the first 30 mins to 1 hour of driving before eventually raising to the correct level. Also during this time the suspension warning light would occasionally - but not consistently - come on while stopped at a junction, only to go out again once I had pulled away.

As I said, the front is now refusing to raise at all:

DSC00682.jpg

DSC00683.jpg

Having checked that there is no pressure in the system with the engine off (no resistance in the control disc at all), I guess I have a leak somewhere. Once I start the car I get resistance in the control disc but this disappears immediately when the engine is cut:

DSC00678.jpg

DSC00679.jpg

DSC00680.jpg

I have tried to bleed the system by loosening the sealing screw on the pressure regulator in case an airlock is causing my problem but all this has resulted in is a lot of hydraulic fluid on the floor and now a visible leak from the screw as indicated in this picture:

DSC00681witharrows.jpg

I am indicating the sealing screw with the red arrow and the pool of hydraulic fluid (the engine was off for the picture, but when on was coming out at a rate of a drop per second, probably) with the blue arrow.

I remember Styria mentioning there should be a rubber o-ring on this screw but mine does not seem to be present - perhaps this is causing problems? However, until I moved this screw yesterday to try to bleed the air from the system there was no leak here, so I'm not sure if this explains my other problems.

As far as I can tell I have the right amount of hydraulic fluid in the reservoir and the pump is working.

What is so frustrating is that the system was working flawlessly (albeit with two minute leaks) but making the car "roadworthy" has resulted in it not working. Aaagghh! What a great example of "if it ain't broke, don't fix it". :(

Any suggestions / theories welcomed!

Thanks,

Chris
 

alabbasi

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Chris

Two things to check. There is a height control valve on the left side of the engine on the firewall (may be on the right for RHD drive cars). The control valve looks like a square box with an arm attached to it. The arm is connected to a rod which looks like a mini tie rod and this connects the arm on the control valve to the body.

If this connecting rod is broken (which can happen as they have plastic centers) then the arm on the height control which controls the self leveling function on the valve will not move and as a result, the car will sit low.

Try lifting the arm up very slightly on the control valve and see if the car rises. If this does not work then get on the bumper and start jumping up and down as things may be stuck. I've had to do this on my Canada spec 6.9. It has huge US bumpers which make jumping up and down easy :).
 

SEL_69L

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Alabbasi: That was exactly the case on my car about 8 years ago. I 'phoned Styria, he correctly identified the problem over the 'phone, and arrived the next afternoon with new plastic part. Cost me about 25 bucks and Styria about 1/2 hour of work.
 

alabbasi

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Alabbasi: That was exactly the case on my car about 8 years ago. I 'phoned Styria, he correctly identified the problem over the 'phone, and arrived the next afternoon with new plastic part. Cost me about 25 bucks and Styria about 1/2 hour of work.

You let Styria jump up and down on your bumper????

You guys are lucky, the US cars have the dreaded automatic climate control servo which is not only problematic but sits right on top of the height control valve which makes access difficult to say the least as there are a pile of stiff rubber hoses and vacuum lines.
 

Styria

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You let Styria jump up and down on your bumper????

You guys are lucky, the US cars have the dreaded automatic climate control servo which is not only problematic but sits right on top of the height control valve which makes access difficult to say the least as there are a pile of stiff rubber hoses and vacuum lines.

Hi Alabbasi, any chance of getting a pic or two of the automatic control servo ? I have heard so much about them, but know absolutely nothing. As far as jumping up and down on the bumpers, I'd never have the heart to do so - the Euro/Aussie bars are quite delicate and need therefore be treated with some respect......Regards Styria
 

Styria

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Hi ChrisP, it's nice to see those pics of "Kaiser" Wilhelm - and him looking in such splendid condition. As you know, we have talked about a couple of matters in relation to the problem, but I was never aware that you had fitted another pump. New ? Second hand ? How good is it, and was it tested ? Please let me know if you can. Yep, on another tack - sometimes it's best to leave well alone, but I concede that you had little choice in the matter this time. Please keep in touch. Regards Styria
 

alabbasi

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Styria

Here are a couple of pictures. The first is under the hood of my 6.9.
IMGP0049.jpg

If you look at the left corner up against the fire wall you'll see the ACC servo with all of those vacuum lines attached to it. On the bottom side, there are a bunch of short, stiff rubber heating hoses that go into it.

Access to the high control valve is not possible with this unit in place

Here is a picture of one close up on a different car (it's tight in a 6.9 so hard to photograph).

s7002596mt1.jpg


The system was designed by Chrysler and went into their cars in the late 60's. It was problematic and i'm pretty sure that Chrysler stopped using it by the time that MB started to.

Common problems with these systems are:

Internal piston would get stuck and drain battery
System would blow hot only
System would only blow on defrost
None of the vents would work.
The servo itself would crack from heat and cause a coolant leak

I have an updated aluminum bodied servo in my car which is less susceptible to cracking and have so far had no issues. Unwired tools makes a digital version which is supposed to be much more reliable. I know of a few people that have bought it but ran into issues installing it. I can't say if the installation issues are the fault of the product or the installer

Going back on topic, if the suspension pump was replaced, check to see that all the bolts are on tight (do not over tighten). If they're not, then it could wreak havoc with the suspension.
 

WGB

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Hi ChrisP,

Where are you living in WA - I seem to remember you were moving not far from me.

As far as your car goes before you start on anything complicated on either the central or levelling valves I would bleed the main line into the central valve by removing the connection at the top end of the pressure hose (after releasing the pressure with the disc disconnected and in the "m" position) . Then aim the disconnected hose into the open reservoir, start the engine and run the pump for a short time until the fluid is definitely clear.

I am flying to Kununnara this Friday for three days but will be home after work the next four nights and if you are not too far from me either I can come to you or you can come to me (as I probably have a bit more useful gear).

The following weekend on Sunday 29th there is a proposed short meet of the WA 116 group if you are interested.

Bill
 
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chrisp

chrisp

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Hello everyone,

Thanks for your suggestions.

Bill: I'm in Darlington. I'm not sure how close that is to you but if you're near Kalamunda it won't be very far, I guess. Thank you so much for your kind offer of assistance! My problem with working on the car in the next day or so is that I don't typically get home from work until after dark and have limited lighting at my new house (we've only just moved in and are just renting which limits rapid permanent solutions with just a car port and a semi-rural location). I can borrow a decent light from tomorrow onwards, though. The car isn't really driveable just now due to this problem with the suspension so if I can fix it in situ then that's the ideal case. If I have to tow it somewhere then I'll cross that bridge as and when necessary. Let me get back to you once I have sorted the lighting issue and once again, thanks so much for offering to help.

Styria: yes, the pump was also replaced when the front levelling valve was. Everything worked perfectly for a few days, then these symptoms of the front not raising properly started manifesting themselves ever more frequently until I have arrived at the position I am in now.

Regards,

Chris
 
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chrisp

chrisp

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Chris

Two things to check. There is a height control valve on the left side of the engine on the firewall (may be on the right for RHD drive cars). The control valve looks like a square box with an arm attached to it. The arm is connected to a rod which looks like a mini tie rod and this connects the arm on the control valve to the body.

If this connecting rod is broken (which can happen as they have plastic centers) then the arm on the height control which controls the self leveling function on the valve will not move and as a result, the car will sit low.

Try lifting the arm up very slightly on the control valve and see if the car rises. If this does not work then get on the bumper and start jumping up and down as things may be stuck. I've had to do this on my Canada spec 6.9. It has huge US bumpers which make jumping up and down easy :).

Thanks - the connecting rod seems fine but jumping up and down is always an option. :) I might do that anyway, away from the car.
 

Styria

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I'll PM you my mobile No

Bill

Hi Bill, thanks for taking 'ChrisP' under your wing - it is a pity that he moved to WA which means that I cannot advise him properly, and whilst he is no 'duffer' from a mechanical point of view, it does help to have some 'intimate' knowledge of the hydraulic system. I was perplexed when I found out that another pump had been fitted as I felt that the unit on the car (when I had it) was perfectly serviceable. Thanks again. Regards Styria
 

Styria

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Hi Alabbasi, thanks for those photos. It's always interesting to see the inner and outer workings under the bonnet of a 6.9, and this car is no exception. I have to say that I am surprised, and perhaps disappointed, to see the state of the engine bay of this particular car. Yep, all those rubber hoses and piping for the Air Con control ceratinly are not a work of art, and I am sure there are not that many more components you could fit under that bonnet - it is full, isn't it - almost worse than the Australian versions, or at least when compared with the under bonnet area of my Gleaming Beauty. Regards Styria
 

Lukas

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I had exactly the same issue on the dark 6.9 on the weekend - back up, front not. I tried:
  • Bouncing / shaking the car in various ways (to move the struts around and try to get some fluid flow happening in case of a blockage somewhere).
  • Playing with the front level control valve (by wiggling the attached arm)
  • Rotating the control disc
  • Letting the engine run for 10 mins in case it was just having a slow day, as well as some revs.

In the end, none of those worked, so I came to TK and read up on bleeding bolts etc. Then went back to the car the next day, tried rotating the disc again a few times and voila - all good. I suspect the system has goo in it, but any flushing will be a while away.
 

WGB

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Popped around and met Chris tonight and had a look at his car.

It is again a delight to meet another true 116 Gentleman and his lovely wife.

He had tried to bleed the pump by loosening the "Throttle Valve" and the brittle O ring had shredded, ceased to seal and blocked the high pressure outlet port from the pump.

Cleaned off the old bits, put in a new o ring and that fixed the leak.

Removed the output line from the pump and bled it into the tank. Steady flow but volume and flow rate was not particularly impressive.

Anyway after this the low presssure light went out and after a longish period the car lifted itself and stayed up.

I guess it will probably need a week or two of running to purge all the air from the system and at this stage hopefully the pump will prove to be OK - if there are still problems my guess is the pump should be a warranty job.

Bill
 

Styria

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Hi Bill, I'll go along with your observation regarding Chris and Michelle - an absolutely delightful couple and I was indeed sorry to see them move away from Sydney. Naturally, I am glad that you were able to help and I am indeed grateful and appreciative of your action. Pretty frustrating to have a misbehaving suspension and not having the right tools on hand - and a bit of knowledge to boot to fix what at times can be a simple problem. Regards Styria
 

Michel

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Great account Dr Bill,

I guess if one day medicine stops paying, there's always specialisation in 6.9s.

thanks for sharing :D
 
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chrisp

chrisp

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Hi Everyone,

First, thank you so much to Bill for coming round in the cold and the dark last night and getting the car to raise again. I am forever in your debt.

This morning the car was back on its knees at the front but a minute or so of 2500 RPM got it to raise. I have driven to work today and I occasionally experienced the warning light coming on at a junction again but the car stayed up, so now I am back to where I was: drivable but not working as well as it has historically.

I was having a look at the Haynes manual - such as it is - this morning and am wondering if I could have an issue with the pressure regulator? If one of the ball valves inside is not closing properly is it possible I could have fluid leaking back into the reservoir?

Either way, I'm thinking I will get the pump checked too.

Regards,

Chris
 

WGB

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The system will be full of air and will probably take a bit of use before it reaches it's normal capabilities.

I would be checking the pump first - but drive it a few times before you decide what to do.

CraigS also proposed in the past to drive it for 30 minutes on the high setting to help expell the air.

Bill
 
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