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MECHANICALS With a 30 year-old automobile, there will always be discussion here - maintenance, modifications and mechanicals.

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Old 17th July 2009, 05:45 AM
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Styria Styria is offline
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Default Removal of 6.9 Master Air Cell

This is probably one of the easiest jobs to carry out on a 6.9, but it pays to know your way around procedure and tool wise.

First off, I disconnect the height adjustment cable and jack up the front of the car - be sure to place suitable stands under the car to support its weight. Then move the adjustment disc on your distribution valve to the "Repair" position as per photograph.


You may/may not require the following tools:

30mm Open End spanner to loosen (only) pressure switch on top of Air Cell.
It cannot be unscrewed completely, and that requires disconnection of the wire from the rest of the system. That only creates hassles.

11mm claw spanner for one of the hydraulic lines.

11mm 'claw' socket spanner for the other hydraulic line.

Normal, short 11mm open end spanner to further undo both hydraulic lines as it is too awkward to further use the claw spanners - they are used strictly to 'crack' the retaining nut.

13mm socket with 'flexible' extensions, and last but possibly not least, a jumbo size 'breaker bar' in case of some stubborn wheel bolts - as can happen when tyre outlets use the 'rattle gun' method of tightening the bolts which happens more often that you'd think. In a situation like that, you could be hard pressed to undo those bolts.

Illustration of application of tools...

Yes, slotted disc rotors are available for our 116s....

You are now ready to unbolt the unit with the help of the small 13mm socket and 'loose' extensions and unscrew the body of the unit from the warning light pressure switch. Hope this helps with your next job. The master cell, whilst not affecting ride quality, is instrumental in maintaining pressure, and holding it, to the rest of the system. It will also prevent the car from 'sinking' when parked overnight. Regards Styria
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Old 17th July 2009, 10:40 PM
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s class s class is offline
Join Date: Apr 2008
Location: South Africa
Posts: 790
Default Re: Removal of 6.9 Master Air Cell


thanks for the nice illustrations. Removing the master cell ought to be an easy job - and so I was reckoning on 20 minutes for the webasto-pre-heater project car I'm sorting out for another guy. Turns out one of the 11mm fittings was rounded off previously, and after a great deal of effort I resorted to visegrips to remove it, in the process totally writing off the fitting. (I have now removed the entire line, which runs under the front bumber and terminates under the battery tray, and I have replaced it). Once I was over that hiccup I thought it would be plain sailing, but guess what - one of the three 13mm retaining nuts that secures the air cell was rusted fast onto its stud - and the welded on stud tore free - result - I had to remove the front valance etc to deal with the stud from behind. So a 20 minute job became a couple of hours.....

When I was contemplating the purchase of my "trusty rusty", you warned me about the misery of rusted fasteners and fittings on euro cars. And true enough, trusty rusty has given me some headaches in this regard, but nowhere near as bad as this dark blue car.
'80 W116 280SE euro - the ride
'76 W116 6.9 euro - trusty rusty
'78 W116 6.9 euro - the AMG
'74 W116 350SE euro - the stand-in ride
'82 W126 500SEL euro - full hydraulics - the limo
'83 FORD XR3 - the beast

0 benzes on stands, 5 RUNNING
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