For a British car launched in the early 1960’s the Jaguar XKE had a relatively sophisticated brake system. All three series of XKE’s had power assisted disc brakes all around. The early 3.8 litre Series I models had a vacuum assisted system with a Dunlop bellows servo unit with a Girling master cylinder. By the time the 4.2 litre Series II cars were being produced this system had been replaced with a vacuum assisted Lockheed dual-line servo system. This consists of a master cylinder on the left-hand side of the car that is connected to the firewall and directly linked to the brake pedal via a short shaft. A vacuum servo unit and slave cylinder is mounted on the left-hand firewall underneath the master cylinder to provide power assist when braking. The vacuum line that powers the servo comes off the intake manifold and runs via rubber hoses and a metal pipe behind the firewall. On the left-hand side of the car there is a large vacuum tank with a check valve that provides some vacuum assistance if one has to brake after the engine stalls. The fluid reservoirs are plastic bottles that sit in a holder on the left-hand side fo the engine.
Although the Jag’s brakes were working, I noted that there was some brake fluid leaking around the pedal and figured on a
pretty complete brake system rebuild as a matter of safety and reliability. This meant at a minimum replacing all the vacuum hoses and brake lines and rebuilding the master cylinder and vacuum servo and slave cylinder as a start. The master cylinder and the servo unit are full of rubber seals and diaphragms that can wear and leak. I had rebuilt master brake cylinders and clutch cylinders on other British cars and figured that the appropriate rebuild kits with various seals would do the trick. In addition, pulling off the master cylinder, servo and vacuum tank would give me good access to really clean-up the lower firewall. As a final point, I had it in my mind to replace the original starter with a more efficient gear reduction starter, and pulling the vacuum tank provides for access to remove the old starter and replace it with the new one. Finally, it is easy to gain access to the brake master and servo once the heater box and fan are removed. I wanted to refinish the heater box and replace all of the water lines in the car – so it made sense to start this process all together. Along the way I took lots of pictures to help me keep straight how everything fit together and particularly where the vacuum, brake and water lines all ran.
I first drained the water down on the car so that I could pull off the heater hoses and remove the heater box. This is very easy as the box is attached to the firewall by four bolts that came off with no problems. It also is attached to one of the engine frame members. The top, sides, bottom and interior of the heater box and fan assembly were a little dirty, and the paint a bit worn, but there was very little surface rust and no pitting. I put these aside for refinishing.
Once the heater box is off, pulling the master cylinder is straightforward. First I disconnected the vacuum lines,disconnected the rubber brake fluid lines that ran from the reservoirs and drained the old brake fluid and discarded it. I then disconnected the two metal high-pressure lines master cylinder. From inside the driver’s footwell I removed all the carpet and the under padding – which was in remarkable like-new shape I might add. I then disconnected the master cylinder brake shaft from the pedal bu removing the cotter pin and withdrawing the clevis pin. This is all done from inside car. There were two nuts that secure the master cylinder and these were easy to undo. I could then take the master cylinder off the firewall. The area of the firewall inside the car and the floor were all remarkably clean. Great.Things were going well and I thought – piece of cake so far. Then I began to dissemble the master cylinder. I could see plenty of brake fluid in and around the rubber boot that covers the shaft. Hopefully this just meant worn seals… The removal of the vacuum servo unit is also very straight forward once the master cylinder if off the firewall. I disconnected all the hoses and metal lines. From inside the car I undid the three nuts that hold the servo to the firewall and it came away with little problem. I lightly cleaned up the exteriors of both the master cylinder and servo unit so I would not get dirt or rust into the cylinders when I opened them. So far so good…