Repairing RR Air Suspension

Had two Rangies in recently, to see if I could do anything with the air suspension, so out with the diagnostic tool and a quick check of the sensors revealed they were OK, and checked the motors which were both running, but putting out no, or insufficient air to run the system; this was confirmed by the fact that none of the dash lights were illuminated for the system as they switch off if there's an air delivery fault.

In both cases it became apparent that the piston rings on the piston were excessively worn and despite me using all my contacts, I couldn't get hold of a couple of piston rings; and if I can't get hold of a couple then we have a problem; the reconditioners won't sell the piston rings separately as they want to charge over £100 + VAT for reconditioned items, so a solution was devised; or as they used to say in Ello Ello, I have a cunning plan.

After removing the piston from the gudgeon pin I measured the height of the piston and put it in a lathe, I turned off the upper portion of the piston back to the piston ring groove and no further, so the piston ring groove was intact. I looked in our engineering plastic and found some Black Nylon bar which is a derivative of normal Nylon 66, but with added graphite for lubrication, hence Black Nylon as its black and not white like normal Nylon 66.

This was bored to fit over the piston ring groove so it was a reasonably tight fit, but oversize for the bore, and was bonded onto the piston ring groove with a water based adhesive, the outer was turned down to the exact dimensions of the bore after they were accurately measured, the underside was tapered slightly which left a tight fitting lip of about 2mm in thickness. With the piston still centred in the lathe I bored a 3mm hole down the centre of the piston and it was opened up to 4.2mm and a 5mm thread was tapped into it. The piston was removed from the lathe and a piece of aluminium was located and turned down to the exact diameter of the original piston and a tail was left for turning down to thread 5mm, it was then machined to thickness, then the thread was die'd onto it, this left us with a one piece piston top which could be screwed to the bottom half of the piston.

Our lower piston was soaked in hot water to release the water based glue, which it did, and the new nylon piston ring was carefully prised off, both the piston groove and inside of the nylon piston ring were lightly sanded with 600 grit wet and dry, used wet, until the piston ring just slid on and turned by hand, the new piston top was screwed on and the protruding thread measured, it was cut of with 2mm protruding, screwed back to the lower piston and the remaining 2mm was peened over to form one piston.

This was reassembled into the pump using a piston ring compressor and a little light oil to lubricate the bore, the gudgeon pin was installed and the unit was reassembled, it works much better than the original split piston ring as it has no air leaking past it, and runs for shorter bursts, its much quieter, and much smoother.

One simple fix for around 1 hours work and about £6 for a length of Black Nylon bar.

Huh ... do keep up! The spoof wartime sit-com was Allo Allo, and it was Baldrick in Blackadder who always had "a cunning plan".

Don't know nuffin' about air suspension, but I know my comedy programmes.

It was Herr flick in Ello Ello who had a cunning plan also.

Know what, that rings a bell, you could well be right - not saying you are mind, just 'could be'. I'll check it out.

Okay, you're right, it was accompanied by his trusty sidekick Von Smallhausen, it was Herr Flick ... but it was still "Allo Allo" not "Ello Ello"! The latter sounds like something Dixon of Dock Green would say.

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Funnily enough, on this weeks "new wheeler dealers" they had an L322 rangie, with a duff suspension compressor, and his fault was the seal on the piston.

He (ed China) couldn't get a seal. so ended up replacing the whole shebang. seemed a waste of money to me. although I suppose most spare parts retailers want to make mega ££££ by "overhauling" a pump (painting and changing the O ring)

Perhaps I should start producing a new piston with replaceable rings, might be a nice little sideline.

I'm sure there are folk out there who would pay a fortune for a replaceable ring!

Care to name any?

Don't know any personally, but people who have "Farmer Giles" and spend their lives sitting on inflatable rings ... if you see what I mean. Why, what did you think I meant? Don't answer that!!!