HI from Bedford TK owner :)

[G-CPTN]

The hydraulic tandem master cylinder is mounted together with the air dual-actuator on the outside of the chassis sidemember, immediately behind the cab.
The cylinder contains two spring-loaded pistons, each fitted with rubber seals. Two detachable plastic reservoirs, each containing a filter, are mounted above tip-type recuperating valves. The recuperating valves are self-contained and interchangeable, and are screwed into tapped bosses in the cylinder so that the valve spindles project into the cylinder bore. The valves are held open by the piston flanges when the brakes are off and close under the action of their springs as the pistons move when the brakes are applied.
Two adaptors screwed into tapped bosses in the side of the cylinder retain spring-loaded check valves and provide attachment for the front and rear hydraulic brake pipes.

Removal:-
1 Disconnect the hydraulic pipes from the master cylinder.
2 Remove the nuts securing the master cylinder and actuator to the support and withdraw the master cylinder. Note the number of shims between the attaching faces as they control the clearance between the end of the actuator pushrod and the master cylinder primary piston.

Dismantling:-
1 Unscrew the reservoir caps and drain off the fluid.
2 Remove the reservoir filters using a length of welding wire shaped with a bend at the end.
3 Unscrew the reservoir retaining nuts and with draw the reservoirs, washers and sealing rings.
4 Unscrew the recuperating valves and remove the sealing rings. Do not dismantle the valves unnecessarily. If required, the valves may be dismantled by removing the spring retainers.
5 Remove the piston stop bolt at the base of the cylinder.
6 Remove the adaptors and sealing rings and withdraw the check valves and springs. Remove the front plug and sealing ring.
7 Remove the circlip at the rear of the cylinder and withdraw the pistons and springs. When withdrawing the secondary piston, use a thin feeler blade to assist the rear seal in passing over the the circlip groove.
8 Remove the perforated plate from the front end of the cylinder bore.

Inspection:-
1 Clean all parts with alcohol (methylated spirits).
2 Inspect the recuperating and check valves for damage or corrosion.
3 Examine the cylinder bore and pistons for ridges or scores.
4 All rubber seals should be renewed whenever the cylinder is dismantled.
If the seals show signs of swelling due to mineral oil contamination, the remainder of the brake system should be checked and flushed out with alcohol (methylated spirits).

Reassembly:-
Note the following:-
1 Smear the cylinder bore and all components with clean brake fluid.
2 Pack the rear seal of the primary piston with the approved grease.
3 Install the pistons and piston seals. Use a thin feeler blade to assist the seals in passing over the circlip groove.
4 Use new sealing rings when assembling the checkvalves to the springs.
5 Assemble new sealing rings to the recuperating valves and install the valves whilst holding the pistons depressed. Check that the movement of the pistons actuates both valves.
6 Position the rubber washers on the recuperating valves and the copper washers under the reservoir retaining nuts.

Installation:-
1 Before installing the master cylinder, determine the thickness of shims required between the cylinder and the support. This may be achieved as follows:-
With the actuator located in the support assemble the shims removed and gauge VR2096, as shown in N25. Add or remove sufficient shims until the pushrod is flush with and not more than .005in below the top of the gauge. As a final check the shims should be compressed by securing the gauge with three nuts.
2 Smear the recess in the primary piston with the approved grease.
3 Refill the reservoirs to the indicated level and bleed the brakes.

Illustration of checking gauge VR2096:- http://i24.photobucket.com/albums/c1...n/IMGP8510.jpg

Illustration of the master cylinder:- http://i24.photobucket.com/albums/c1...n/IMGP8512.jpg

(Without the checking gauge VR2096 - which will undoubtedly be the case - the depth of the depression in the master cylinder piston must be calculated such that there is no free play or lost movement when the cylinder is attached to the air actuator, nor must the actuator pushrod cause movement of the master cylinder piston before air is applied - although it might be necessary for trial and error of the number and thickness of the shims until satisfactory operation is accomplished.
It might be advisable to measure the dimensions of the air actuator pushrod and the depression of the removed master cylinder piston to determine how much clearance or preload is required.)

[G-CPTN]

Removal:-
1 Release the air pressure from the system.
2 Remove the airlines from the actuator and the hydraulic pipes from the master cylinder.
3 Remove the four bolts from the cylinder and actuator support and withdraw the assembly.
4 Remove the three nuts and lockwashers and separate the master cylinder and actuator from the support. Note the number of shims between the master cylinder and the support as they control the clearance between the actuator pushrod and the master cylinder primary piston.

Dismantling:-
1 Mark the position of the cylinders in relation to the body.
2 Remove the bolts and separate the cylinders from the body. Remove the gasket.
3 Withdraw the piston assembly from the rear cylinder and remove the lubricator felt.
4 Withdraw the filter from the front cylinder. Remove the friction disc and withdraw the indicator rod.
5 Secure the pushrod assembly in a soft-jawed vice and remove the pushrod locknut. The spring tension can be overcome by hand pressure.
6 Withdraw the pushrod from the piston and body and remove the pushrod thrust washer. Remove the piston lubricator felt.
7 Remove the circlip from the body and withdraw the washers and felt ring. The filter in the body should not be removed unnecessarily.
8 Do not remove the seals or sealing rings unless replacement is necessary.

Inspection:-
1 Wipe the rubber components with a clean, dry cloth and was all other parts. Clean the filters.
2 Examine the sliding surface of the pushrod for scores and the bush in the body for wear. The rod should be a close sliding fit in the bush.
3 Examine the pistons for damage and the sliding surfaces for scores and wear.
4 Check the cylinders for dents or signs of scoring and corrosion. Slight corrosion may be removed with fine emery cloth.
5 Examine all rubber parts for wear, damage and deterioration.

Reassembly:-
1 Smear the seals, sealing rings, pushrod, bush and the sliding surfaces with the approved grease. Soak the felt ring and piston lubricator felts in the approved lubricant.
2 Press the seal into the body with the plain side to the bush. See fig N39. Insert the felt ring, with a washer on each side, into the body and secure with the circlip.
3 Assemble the seals to the pistons with the plain side towards the lubricator felt groove. Locate the sealing ring in the piston bore.
4 Place the thrust washer on the pushrod and position the piston with the boss in contact with the thrust washer. Care should be taken to avoid damaging the sealing ring.
5 Place the body on the pushrod with the air inlet port adjacent to the piston. Care should be taken to avoid damaging the body seal.
6 Position the pushrod return spring on the body and locate the retainer on the spring. Compress the spring using hand pressure and fully tighten the pushrod locknut.
7 Assemble the sealing ring in the groove in the body and the lubricator felts in the piston grooves, ensuring that the ends of the felt do not overlap.
8 Insert the rear piston assembly into the cylinder with the single mounting stud. Care should be taken to avoid damaging the piston seal.
9 Position the cylinder, together with a new gasket on the body and align the marks made when dismantling.
10 Install the indicator rod in the front cylinder and retain with the friction disc.
11 Position the cylinder on the body and align the marks made when dismantling. Insert the bolts and tighten the nuts to the specified torque. (18 lb.ft)
12 Install the filter in the cylinder.
13 Place the blanking disc in the recess in the front cylinder and position the support on the actuator. Install the master cylinder as described under 'Master Cylinder'.

Installation:-
1 Bleed the hydraulic brake system.
Check the airline connections for leakage.

Illustration of the air dual actuator:- http://i24.photobucket.com/albums/c1...n/IMGP8509.jpg

[G-CPTN]

Bleeding the hydraulic brake system:-
1 Charge the air system to operating pressure and adjust the wheelbrakes.
2 Remove the filler caps from the hydraulic master cylinder, and, if necessary, top up the fluid levels.
3 Clean each bleeder screw and attach a length of rubber tube to one of the rear brake bleeder screws. Place the other end of the tube in a glass jar filled with sufficient brake fluid to immerse the end of the tube.
4 Unscrew the bleeder screw two or three turns and employ an assistant to operate the brake pedal until all of the air bubbles cease to appear from the end of the rubber tube.
The fluid level must be maintained above the minimum level indicated on the reservoirs during the bleeding operation.
5 Tighten the bleeder screw, remove the rubber tube and repeat the operation on the remaining brakes.
6 Top up the fluid level to the maximum indicated on the reservors, ensure that the vent hole in the caps is unobstructed and replace the caps.
7 Push the air actuator indicator rod until it contacts the piston.
8 apply heavy pressure to the brake pedal and check that the indicator rod does not emerge to reveal the red band, as this indicates the presence of air, leakage in the system or incorrect brake shoe adjustment.This must be corrected by further bleeding and/or adjustment after examination of the hydraulic system.

The fluid bled from the system must be discarded as it contains air (and must not be used for topping up the reservoirs).

[G-CPTN]

And finally (at least for now):-
Footbrake valve operating test.

1 Disconnect the airlines to the master cylinder actuator at the footbrake valve and connect an air pressure test gauge to each port.
2 Charge the air system to operating pressure.
3 Fully apply the footbrake and check that the pressures registered on the test gauges are approximately the same as registered on the vehicle gauge.
4 Release the brake pedal and check that the pressures fall immediately to zero on the test gauges.
5 Re-charge the system and gradually apply the footbrake. Check that the pressures registered on the test gauges are within 7 lb/sq in at pressures below 25 lb/sq in and within 5 lb/sq in at pressures above 25 lb/sq in. The pressures should increase with brake pedal effort until they are the same as registered on the vehicle gauge.
6 Check the pressures again while slowly releasing the brake pedal.

Leakage test:-
1 Charge the air system to operating pressure.
2 Smear the footvalve exhaust diaphragm and the dust cover with soap solution and check for leakage. Leakage indicates faulty valve carrier sealing rings or inlet valves and/or seats.
3 Fully apply the brake pedal and again check for leakage from the exhaust diaphragm and the dust cover. Leakage in excess of a one inch soap bubble in five seconds indicates faulty exhaust valves and/or seats, or piston sealing rings, or valve carrier rear sealing ring.
4 Smear the valve body and airline connections with soap solution and check for leakage with the brake pedal fully applied.

[MazTalks]

ok, thanks, hubby is home this weekend, so i will ask him nicely if he can help me to do the wheel brake adjustment

[Ian]

Well G-C what can one say, I suggested MazTalk joined T&B (With her problematic Bedford) knowing that you would be able to help, I didn't envisage the chapter and verse that you have delivered. I SHOULD have known BETTER. . . . .What a Super job you have done.

A well deserved Thank you.

[coastie]

That's G-C for you! Always loves researching things untill a solution is found.

[MazTalks]

Thanks again for all your help. The parts are ordered and hopefully will arrive next week and then the mechanic can get on and fix it !

[G-CPTN]

I hope you are able to print out the instructions (and the illustrations) for him (even though they are in English).
The illustrations should help even though they are not in French.

[MazTalks]

I will certainly try
The pictures should help him !