DE model servo

Descriptive and in-depth articles on how to do repairs or restoration.
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Roark
Posts: 110
Joined: Sat Feb 13, 2016 10:52 am

DE model servo

Post by Roark » Mon Jun 25, 2018 1:43 pm

Thanks to the good offices of Peter Grant I have been in contact with someone in Australia who has made new seals for the Clayton deWandre servos fitted to DE models.

On that basis I decided to strip the servo on my car in order to clean it both inside and outside. It's a strange item. The main body has a large and long but soft spring attached to the piston which, one presumes, must have some oil around it to lubricate the seals. However, the owner's handbook does not mention what lubricant should used or even how much should be used.

There is a bellows on the top through which one rod moves and there is a rubber sleeve on the other. Apparently there are also some smaller seals in the brass block on the top. However, while there is a drain plug at the bottom I do not have any idea of what oils to use and how much. Does anyone have any idea please?

Roark
Posts: 110
Joined: Sat Feb 13, 2016 10:52 am

Re: DE model servo

Post by Roark » Mon Jun 25, 2018 5:12 pm

The servo is now stripped to a bare shell and i have spent a lot of time cleaning the various components. However, on top of the servo is a small brass block with a shorter length of studding sticking out. It appears to be sprung loaded and while I have removed the securing nut on end end I cannot find a way of removing the piston in order to replace the seals inside the block.
Does anyone have any clues please?

Christopher Storey
Posts: 165
Joined: Wed Mar 16, 2016 6:40 pm

Re: DE model servo

Post by Christopher Storey » Wed Jun 27, 2018 9:10 am

If the seal is rubber the seal lubricant will be red rubber grease . You can buy a lifetime's supply for about £10 :D :D

If by any chance however it is leather, as in the larger lorry type Clayton servos, then light hydraulic oil will be the preferred lubricant .

As far as dismantling is concerned, I imagine that the brass block should be unscrewed up the studding . The nut you have removed will probably be merely a locknut for the brass block

Roark
Posts: 110
Joined: Sat Feb 13, 2016 10:52 am

Re: DE model servo

Post by Roark » Wed Jun 27, 2018 9:47 am

Thanks to some help from Mark Bearman in Australia it seems the seal and the whole servo is lubricated by the chassis lubrication system. However, that doesn't give any indication of how much oil should be in the servo. If it's fed by that system one would suspect that the servo would need to be drained occasionally.
The main piston seal is a curious construction and made of leather largely. There are companies who specialise in spares for the lorry type servos and the DE models have one that could have been used on a lorry. The braking system is the same as for the 4 ton ERF and Ford of the early fifties.
I have managed to remove the pistons from the distribution block but have muddled up the re-assembly of the operating rods. Hopefully Mark will be able to supply some diagrams

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