Advice and guidance on repair and restoration techniques.
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Location: Lewes, East Sussex

Servicing an Aristocrat damper pump

Postby coppinpr » Wed Feb 12, 2014 8:28 pm

This is all very easy and doesn't really need describing as it's common sense really, but as I've been doing one I thought I'd put up info and photos in case any one needs to see.

This pump looked great but had no pressure at all. It comes from an Aristo Nevada that had been sitting, indoors, in a spare room for 20 years, so I suspect drying out was the cause of the failure.
Like almost all Aristo parts, it's well made, easy to work on and built to last. Attached to the case with split pins at each end, it's easy to remove from the case.

Once the unit is free from the case, remove the adjustment screw completely, then undo one end of a set of retaining rods and remove the brackets at each end. At this point you should have a sealed cylinder with the piston rod protruding from its entry hole. If the pump has no pressure at all, the reason should be obvious at this point - one end or the other of the cylinder has come loose, usually the end with the rod. Looking at the open cap, it's clear that the ends were not just held in place by tightening the the retaining rods. That is what keeps the ends on over a period of time, but a light glue had also been applied at the factory, just enough to hold the ends on and help with the air tight seals on the ends. If both ends are still sealed you will need to loosen one off too gain access to the piston.

The piston consists of the rod and the piston head. The head can be easily removed from the rod but you do not usually need to do so.
The main cause for the pump failure, other than the loose cylinder ends, will be the drying out of the rubber flange and the pressing inwards of the soft metal pegs holding it in place. These pegs can be seen in the photo below. If the flange has completely perished, you will need to remove it and cut another from a suitable leather or rubber material. If, as is more likely, it's just dry, rub a little light oil into it and press the metal pegs out very slightly to make a tighter fit. Very little movement is needed to tighten the fit.

Clean the cylinder and make sure the air holes are clear, then replace the piston and check it moves freely but with some resistance (not much) even without the adjustment screw in place. Reassemble the unit, but first you will need to seal the loose cap. A thin layer of a light glue will do the job but I decided to place a washer inside the cap and tighten the retaining rods against this instead. Should I need to open the piston again it will be easier that way. All that is needed then is to replace the adjustment screw and set it at the desired pressure making sure to lock it into position with its locking nut. Job done !!THUMBSX2!!
rebuilt pump.jpg
Pump unit
pump parts.jpg
Pump parts
pump head.jpg
Piston flange

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Joined: Fri Apr 26, 2013 4:33 am

Re: Servicing an Aristocrat damper pump

Postby rod71 » Fri Mar 07, 2014 5:18 am

Are these hard to come by?. I'm needing one for a Regal thats missing it entirely. :(

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