question Clayton Dewandre Hydrovac Brake Servo

[Dave Jenner]

Hi all...I'm looking for any information I can get hold of regarding these Hydrovac Brake Servos that were made by Clayton Dewandre of Lincoln. I have one that will not work removed from an Alvis Salamander. It would develop a good vacuum, it had been bled through and I could hear and feel the piston moving within the power cylinder, despite this there was none of the normal 'feel' of any servo assistance at the brake pedal. Upon removal and stripping it down there was no obvious signs of any wear and tear; there seemed to be a rather excessive amount of oil in the power cylinder, but this was not as a result of a leak back through the push rod seal. In fact all seals seemed to be in good order with the exception of the cup seal in the hydraulic piston.

 

Could the following be a reason for no servo assistance; if the cup washer/seal in the hydraulic piston was not working efficiently, could, when the engine is running and a vacuum produced, the power cylinder piston move forward under vacuum and push the hydraulic piston forward with no braking effect due to failure of the hydraulic piston seal? (if you get my drift).

 

Anything on this would would be greatly appreciated, as always! Dave

[Dave Jenner]

Reading this myself again, I realise that the power cylinder piston should not move, even with a faulty seal, unless air moves in behind the power cylinder piston to allow it to move forward ie when the brake pedal is applied. Back to square one!

[roy meddings]

i have new ones in stock

 

[Rootes75]

Do you have other types aswell? Our 1950 Commer has a clayton dewandre type VH which we have been having troubles with.

[andym]

I think that Alvis Stalwart owners might be interested too!

Andy

 

Figure G22.pdf

[Richard Farrant]

23 minutes ago, andym said:

I think that Alvis Stalwart owners might be interested too!

Andy

 

Figure G22.pdf 299.07 kB · 1 download

The only thing to be aware of is that Stalwart brakes use Mineral oil in the hydraulics, whereas most commercial vehicles would be using conventional brake fluid. The seals would have to be suitable for mineral oil.

[andym]

2 hours ago, Richard Farrant said:

The only thing to be aware of is that Stalwart brakes use Mineral oil in the hydraulics, whereas most commercial vehicles would be using conventional brake fluid. The seals would have to be suitable for mineral oil.

Agreed!

[Dave Jenner]

4 hours ago, andym said:

Agreed!

Hi Richard how you doing.  I explained that also to the fellow that recently found and acquired his own Mk6...re the mineral oil. 

[Richard Farrant]

1 hour ago, Dave Jenner said:

Hi Richard how you doing.  I explained that also to the fellow that recently found and acquired his own Mk6...re the mineral oil. 

Hi Dave,

I'm good thanks, still firing on all cylinders! Are you still involved with Steve's museum collection?

[Dore-Blanch]

On 8/25/2020 at 2:40 PM, roy meddings said:

i have new ones in stock

 

Hi there, I’d be interested in this. Having problems sourcing seals for the one on my Karrier gamecock

[Harry Backhouse]

Hello, I have a Clayton Dewandre servo pump fitted to a Perkins engine, it is a rotary pump with 4 vanes which slide in the rotor to engage the cylinder, I am looking for 4 new vanes for this pump. I have searched the internet and cant find a similar unit, can anyone help please?

Thanks.

Harry