The Master Cylinder

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Having successfully replaced the rear wheel cylinders and front callipers I was now confident that the brakes would be approaching the standard that Henry Ford designed them to be back in the 1970’s. The new brake pipes and hoses further reinforced my confidence that, if I needed to stop in a hurry, I would be able to without the fear of a hose or pipe splitting. With age, rubber hoses can deteriorate and, even if they do not split, they are more likely to bulge under heavy braking thus reducing the amount of effort we transfer from the brake pedal to the brakes. Put simply, we are putting our effort into expanding the hose rather than putting the brake on. This is why rally cars, high performance cars and a lot of motorbikes now use steel braided hoses.

Master Cyl (1)I now turned my attention to the master cylinder. When I first checked the car over I noted the brake fluid in the reservoir appeared to be dirty with what looked like sediment in it. As I did not wish any of this fluid to go into the new callipers or cylinders I had already disconnected the two pipes connected to the master cylinder and drained the system.

IMG_0025 (2)The master cylinder and reservoir are secured to the servo with two nuts and a simple matter to remove. Once on the bench it was clear that the cylinder bore was badly deteriorated. An attempt to dismantle it further was thwarted when the plastic reservoir steadfastly refused to detach itself from the metal cylinder. Although, only a push fit, the plastic appeared to have bonded itself to the seal and, despite careful prising and pulling, the reservoir eventually cracked. According to the internet this is not an unusual problem.

I now needed a new master cylinder and reservoir. Research had already informed me that master cylinders for mark 3 Cortina’s were like gold dust and fetching ridiculously high prices. A used one had recently been sold on e-bay for almost £200, and I wanted a new one. I didn’t want to chance second-hand. Internet forums referred to using Land Rover parts on some Ford Capri’s and Ford based kit cars but nothing specific to Cortinas.

More research confirmed that a pre 1980 series 3 Land Rover master cylinder had the same external dimensions, but that the piston diameter was bigger. My knowledge of hydraulics told me that the bigger piston would move more fluid in the system for the same amount of brake pedal travel. Simply, if the brake pedal travel was originally 50mm, with a piston that is twice the area the pedal travel would be 25mm. Would this be a problem, only one way to find out, buy one and try it.

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I ordered a cylinder (part number 90577520) from Paddock Spares at a cost of £53.94. This was delivered promptly and I set to work. The first difference was the reservoir, on the Cortina the master cylinder slopes up towards the front and the reservoir is shaped so the top of it is level. I guess not all Land Rover cylinders slope, and, despite the picture on the supplier’s website showing the shaped reservoir, the one they IMG_0020 (2)sent had a reservoir that was intended to be fitted level. Undeterred I attached it to the Cortina servo and, using a spirit level, I could see that, despite the reservoir not being level, the amount of fluid could still reach the maximum mark. So far so good.

 

IMG_0028 (2)Next to fit the two brake pipes, Cortina’s have metric brake pipe unions and, as I discovered, Land Rovers have UNF. Hence the brake pipes would not screw into the ports on the master cylinder. A quick look under the front of the car revealed that both the brake pipes terminate at unions under the front of the car so removal was quite easy. My initial thought was to ask my local garage to cut the metric unions off and fit appropriate size UNF ones, but we decided it was best to have new pipes made up with metric threads at the lower end and UNF at the top. This way the original pipes could be archived and reused if it was subsequently found the Land Rover master cylinder was not suitable. This, of course, would still be dependent on locating a Cortina cylinder.

The pipes were made up and fitted without any problems and the reservoir filled with new fluid. Before fitting the master cylinder to the car I “bench bled” it. This process requires you to pour fluid into the master cylinder outlet ports and reservoir and gently work the piston in and out with a clean non-metallic object. The idea is to ensure the seals are lubricated with fresh fluid and that no air is trapped in the bores. This is particularly important with the Cortina as the master cylinder is mounted on an angle. Having completed the “bench bleed” I used two plastic bungs to seal the outlet ports whilst I fitted the cylinder onto the car. A quick removal of the bung followed by a quick fitting of the pipe ensured only a small amount of fluid leaked out. Be quick but careful when fitting the pipes and do not use a spanner until you are certain that they are not cross-threaded. A damaged thread could cost you another master cylinder.

There are some good videos on YouTube on bench bleeding master cylinders, but I found the above process works well.

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And so to bleeding the system. I had purchased a Gunson Eezibleed pressure bleed bottle from Halfords for £19.99 and I would recommend this as a worthwhile purchase. There are cheaper alternatives but they are little more than a pipe with a one way valve and, in my opinion, are of limited use.

With the Gunson kit fitted and pressurised and, starting at the wheel furthest from the master cylinder, I opened the bleed screw and bled the rear brakes. I then bled the front brakes and, full of confidence, pressed the brake pedal down. Yes, it felt like a good brake, I pressed a bit harder and the pedal went slowly to the floor. There must still be air trapped in the system. I bled the brakes a second time, then a third, the pedal always went to the floor. Give up for the day!

The following day, after much thought, I removed the master cylinder and repeated the “bench bleed” again. Refit the master cylinder and bleed the brakes again. Exactly the same. At this point I noticed that as the pedal went down the level in the reservoir went up. It appeared that the master cylinder was in fact allowing the fluid back into the reservoir rather than feeding it out to the brakes. Time to contact Paddock Spares, I explained the situation and was given a returns number. They said that the cylinder would be examined, and if faulty, I would receive a refund. As I still needed a master cylinder I had to order and pay another £48.94, however I was not charged postage and it was sent express delivery and arrived by 11.00 am the next morning. Within half an hour it was bled, fitted and worked perfectly. Time to put the wheels on, clip the brake pipes neatly in place, and go for a road test.

Westwood  (3)A gentle drive and application of the brake gave me a good feeling, the pedal was firm and the car came to a halt with a significant dip of the front end. A longer road test and I was happy and confident with the cars ability to stop. Conclusion, Land Rover master cylinders, whilst not being a direct replacement, are an acceptable alternative and preferable to putting new seals in a worn master cylinder or buying a used one of unknown condition. With new callipers, wheel cylinders, master cylinder, pipes and hoses my overhaul of the brakes was complete.