my 6.9 can't get it up !

[HansKruger]

I can understand why DES sold this car, it must be painfully annoying with these continual problems




Regards

Hans

 

[SELfor50]

I can understand why DES sold this car, it must be painfully annoying with these continual problems




Regards

Hans

I don't think the problems are "continual" at all??!! Ian, Des, maybe you can shed some light.

I think Ian has only recently experienced issues, and instead of going to a mechanic and getting a$$ raped for several thousands of dollars (cause they won't bother diagnosing, instead just replace everything in the hope it will fix the problem) he's trying to troubleshoot the issue himself.

From what i've seen of B13's 6.9, it's a pretty good example.

 

[SELfor50]

Could it be that the replacement pump has some issues??

 

[TJ 450]

It could indeed be another dodgy pump... I would check the flow rate again. Given the behavior it sounds like the problem lies in the area of the pump, reservoir and pressure regulator/distribution valve.

My experience is that the system will not pressurise if there is air before the pump, ie the fluid has drained back to the reservoir due to the fitting at the base of the pump leaking air back into the system. Conversely, I think it is still possible that this fitting is leaking air back into the system whilst not operating, but expelling negligable fluid whilst running, as this is on the suction side.

So, perhaps there wasn't a problem with the pump per se...?

Tim

 

[CraigS]

I thought the hydro system on 6.9s, at least by 1979, was self-bleeding (just drive the car vigorously for a while)? Also when the suspension did pressurise at the front properly, all 5 spheres and 4 hydro-struts behaved as they should, giving the normal 6.9 magic-carpet type ride.

Help?

Ian.

It will not bleed by itself, but you can try running it on the high setting and taking it for a long drive, then bring it back to the normal level, assuming it will rise while you are driving it. Try twisting the dash knob to see if you can get the light to come on. Sometimes they need a bit of twisting.

 

[HansKruger]

I don't think the problems are "continual" at all??!! Ian, Des, maybe you can shed some light.

I think Ian has only recently experienced issues, and instead of going to a mechanic and getting a$$ raped for several thousands of dollars (cause they won't bother diagnosing, instead just replace everything in the hope it will fix the problem) he's trying to troubleshoot the issue himself.

From what i've seen of B13's 6.9, it's a pretty good example.

You must forgive me then from reading the information here it seems the problems have been ongoing since Des sold the car




Regards
Hans

 

[B13]

You must forgive me then from reading the information here it seems the problems have been ongoing since Des sold the car

I've been driving a variety of W116s since the mid-1990s and this one is no more or less problematic than any other one I've owned. They are old, high-milage cars by these days... my only regret is that I love the cars but never have the big $ needed to buy the ultra-low milage examples...

My car's hanging in there... its robust enough for the daily grind asked of the old girl.

It will not bleed by itself, but you can try running it on the high setting and taking it for a long drive, then bring it back to the normal level, assuming it will rise while you are driving it. Try twisting the dash knob to see if you can get the light to come on. Sometimes they need a bit of twisting.

The warning light is always on. I disconnected the cable and there is no feeling again in the distribution valve detents again. Car feels and acts more or less than same as before I changed the pump. New pump output is heaps better than the old pump's. Am reluctant to do anything at the moment incase it drops and doesn't lift up again... might have to wait until I next have holidays because, rather stupidly I now admit, this is my only car...

I.

 

[CraigS]

The warning light is always on. I disconnected the cable and there is no feeling again in the distribution valve detents again. Car feels and acts more or less than same as before I changed the pump. New pump output is heaps better than the old pump's. Am reluctant to do anything at the moment incase it drops and doesn't lift up again... might have to wait until I next have holidays because, rather stupidly I now admit, this is my only car...

I.

With the cable disconnected, and not running, what happens when you move the adjustment slide by hand ? Any noise or movement ? Try same with the motor running.

 

[Styria]

Reading between the lines, I suspect that B13 has already tried that, with engine running as well, although I stand to be corrected.

If I recall, Michel had similar problems with his 6.9 at one stage, with the disc when moved not responding to any changes in any position. Apparently no amount of 'cajoling and playing' with the pressure regulator improved the workings of the front end until the pressure regulator was exchanged. I have reason to believe he's had no further problems since. Regards Styria

 

[B13]

With the cable disconnected, and not running, what happens when you move the adjustment slide by hand ? Any noise or movement ? Try same with the motor running.

To use erectile parlance (in keeping with the thread title) I presume you mean the control disc with the cable disconnected...

Prior to changing the pump the control disc moved flaccidly with no resistance, consistent with the control valve not being pressurised. This was the case when the engine was running or not.

Changing the pump it was a pig to bleed but the system did finally pressurise and the control disc became erect (stiff, with prononced detents) whether the engine was on or not, and in the H setting with the engine running, car would lift as expected.

Now we're back to where I was before changing the pump, the control disc is flaccid.

I filled the fluid up last night to just above the high marker on the dipstick (previously it had been about 1/2 way between the high and low marks) and bled the system again but no luck yet. Light is still on and I'm not on a highway so can't drive long at elevated constant revs in the H position as WGB suggests at the moment.

Looking at it today the back seems a bit higher than normal... Front still looks normal, slightly lower than I would like but no where near completely sunk. I figure its a safe condition to drive in at the moment. I still have the old pressure regulator/control valve so might look to putting those back in as a form of diagnosis.

Ian.

 

[WGB]

When you say bled - I assume you are meaning disconnected the pump output line and aimed it into the reservoir.


Is there a good flow when you do this or is it weak like it was before the pump change?


Bill

 

[B13]

Yes I did that Bill. This pump is rather better, much more flow at idle and from about 1500rpm onwards theres a strong constant flow.

 

[WGB]

Yes I did that Bill. This pump is rather better, much more flow at idle and from about 1500rpm onwards theres a strong constant flow.

If the valve plate is moving freely without detents with the engine rotating and good oil pressure is to be had from the pump it would suggest it is not receiving that pressure.

?Have you checked the small mesh filter in the valve body inlet from the pump in case it is obstructed

?Has a piece of crap gone up the line and into the valve body - my car has had this small filter removed and they are no longer supplied by M-B.

Bill

 

[B13]

Here's something which might be worth mentioning... rubber O rings...

When I cleaned the small mesh filter I noticed the O ring around the thingy which holds it in seems to have shunk a bit, didn't seem to be offering much of a positive seal... but the thingy didn't leak externally, so I didn't think to much of it... whats the purpose exactly of that O-ring?

Also..

At the interface between the pressure regulator and the control valve is another small O ring, that was flat, and didn't seem to offer much of a positive seal... again, whats the purpose of it? You can see it if you withdraw the two long bolts which hold the control valve to the pressure regulator, and also the cable holder to the control valve.

Ian.

 

[TJ 450]

The o-ring on the closing plug is simply its seal. The one between the dist. block and regulator is the same. I suspect the latter needs to be performing it's function as pressure might bleed off otherwise? Those o-rings are only a few bucks from the dealer, stock in Melbourne last time I ordered.

Tim

 

[s class]

The tiny o-ring between the distribution valve and pressure regulator only seals the path for excess fluid returning from the 5th sphere back to the reservior. I don't think it can be responsible for your troubles.

 

[B13]

Could it be an area where air is drawn into the system when the engine is shut off and the pressure from the pump and therefore within the pressure regulator drops to zero?

I.

 

[s class]

I don't think so - if you were getting air in between the pump and regulator, or in the regulator itself, the problem would self-bleed, provided the pump was delivering. If the pump is indeed good, and its not drawing in air on the suction side, then I'll suspect the pressure regulator.

 

[s class]

BTW, after the initial suspension rebuild on trusty rusty, it took me some time to get it going properly, then it worked, but with some external leaks. I tookl care of those while the car was on stands for engine work (5 months on stands). When I eventually got it going again, it the front end would drop 3 inches overnight. Considering what I had spent and what I had replaced, I was not exactly happy. I then drove the car daily for a week, and in fact rather thrashed it. THis cured all my troubles, The car has now been standing in one of my garages for the last 4 weeks, and in that time the front has sunk only about 3mm, the rear not at all. Very nice.

 

[B13]

Considering what I had spent and what I had replaced, I was not exactly happy.

I guess as 6.9 drivers, really the only thing we don't want to be exactly happy about is the petrol economy.

I'm going on a highway trip this week, should be about a 200km round trip with an average speed of 110km/h so I see how that goes.

Ian.