Master Cylinder Upgrade To Dual Reservoir System


All from Mustang Maniac or blog link click here

Dual Master cylinder, proportioning valves for the rear, and the back pressure valve for the fronts. £300

Hardware fittings & various pipes – £15

25 of 3/16ths copper pipe – £10


If you have been following the progress so far you will be aware that I was ready to bleed the brakes. New brakes all round had been installed, new brake lines had been installed and the single master cylinder had been restored and put back on.

I was ready to start the bleeding process and topped the reservoir up, pumped the brake a few times very gently and started the vacuum at the rear. I was checking for leaks and nothing. That was until I started to give the pedal a little bit more movement. Checking again I found that the master cylinder was leaking at the rear between the brake booster and the cylinder. It was a pretty waterfall to say the least! Then it was a race against time to empty the pot and mop the mess up.

After speaking to the guys at Mustang Maniac I was offered the choice replace the single cylinder for about half the money, or go for the dual set up which will be safer and will not need replacing if I go to discs at a later date, (which I will). Like I have said before – no brainer. Dual system it was and I would have to be extra nice to the wife! The down side – it will not be original, BUT, the brake booster I have in my car was for a manual version and I have an automatic. This is not surprising as it was an optional extra and the garages fitted what ever they had around at the time. There were a few weird combinations out there.

New kit ready to be fitted.


The first part was dead easy, removing the original brake booster. I have a quick link here, or go to the Photos – Engine Bay – Brake Booster Project. I undone the pipe feeds and the then removed the single cylinder which was held in by two bolts. Then remove the booster itself via the four nuts to the rear.

With the booster out-of-the-way the this will expose the mechanism for the brake pedal. As this was fitted with the manual version there is a lever that pushes the master cylinder (I will call this the MC from now on), these brackets had to be removed. In order to remove the bracket it was time to get inside the car and twist yourself into position to remove the brake retaining pin. This is located near the bushes at the top on the left hand side and also holds the brake switch in place. The pin is awkward to get to, but a pair of long nose pliers can get to the end and pull the pin out. Once the pin is removed retain the nylon washer from the outside, gently lever off the bar that goes to the cantor lever at the other side of the fire wall. At this point the brake switch will simply lift off. Inside the hole of the bar is another plastic washer that will sandwich one side of the switch. It is important to get these the correct way round.

Tip: At this point it is a good idea to check the pedal bushes.

It was a little tight to remove the connected brackets but a 3/8ths drive and a shallow socket made light work of it, providing you have a small movement on the ratchet itself. You could remove the pin at the bottom and take of each side independently but I opted for the whole lot. It caused me no issues. The other side was just as awkward but the socket set worked just as well. Once removed I was able to treat the light surface rust ready for the next part.

Things were going well until the new brackets were to be installed. These had to be removed from the back of the dual MC and bolted on in place one at a time. The holes were rusted up a bit from forty-seven years of grime so they needed a clean and a little WD40 sorted that. The gap was tight, I mean real tight. I couldn’t get a socket in the space and the work had to be done by spanners, shorter the better, a little stubby set would be ideal. I had to do a flat turn at the top then go underneath then another flat, back to the top etc. It was time-consuming and painfully slow, not a job I want to do again in a hurry. Stubby spanners would have allowed easier movement and would probably been quicker. I soldiered on and got the left side (as you look at it) in place first. The right hand side is so tight, looking back at it would have been easier to do the right side first. The new brackets are mounted lower down the firewall for two reasons. The first will allow the MC to fit under the tower brace, and secondly the pedal will have a direct push to the cylinder and not via a series of levers higher up.

Once the brackets were in place things go a little easier. I offered up the new booster and noticed that I needed more brake pipe to go where I wanted. I removed the new booster to allow the new pipe easier movement at this point. Previously I left more than I needed and made extra loop just in case of this sort of thing. But, I still hadn’t left enough. So I had to take the old pipe of that hasn’t even been used yet and replace it. Starting at the back I made a new flare using the Blue Point double flaring tool TF5A (review here). I then re-routed the pipe back up to the top of the engine bay. I carefully bent and applied the brake line to where it roughly should be and left plenty of room to bend into place at the top.

I removed the damaged part of the grommet and made it just a lip around the metal fire wall to stop any chaffing on the new rubber. I refitted the booster in place and everything slotted in place just fine. Now was time to get back into the car and refit the brake pedal connections. You will notice the rear of the MC is threaded and not a solid bar. The connection to the pedal is also hollow threaded and need to be screwed into place to adjust the desired height of the pedal required. There was a technique to this, attach the pedal connection to the threaded end and turn, due to the angle of the fitting you have to move the pedal back and forth a little at certain points to get a nice even turn. I kept offering up the pedal to the fitting to see where the height of the pedal was. I set this about an inch higher than the gas pedal. Once I was happy with the pedal position, I then applied the nylon washer to the pin fitting and tucked the brake switch back over the top. Slide the whole thing over onto the locating pin and apply the other washer back to the outside. Then was the fun bit. Trying to get the locking pin back in place was a pain, if I had of had the seat in place it would have been very difficult to say the least. After a few attempts it eventually snapped into place. Tighten the locking nut up to the fitting to stop movement, now the inside was complete.

Next was the proportioning valve to the rear.  This will adjust the brake balance and stop the back of the car overtaking the front under heavy braking. defiantly not original spec, but modern technology solution to an old problem. The adjustment valve has clearly marked in and out which must be followed. The valve is mounted on a custom bracket that fits between the MC and the booster. The valve is then held in place by two nut and bolts. The pipe work was coiled around underneath to give the movement if required and allow for adjustments later if required. I sort of enjoyed making these loops up as it was rather therapeutic. The built in pressure valve is at the front of the reservoir outlet itself so no need for the inline like the fronts.

The bracket was secured to the booster bolts and ready for the front connections. The original bracket now obviously has a gap where the rear pipe would have been. I fitted a blank of connection and made up a tiny flare just to make the seal. The inlet port of the junction box needed a regulator 10psi valve which is inline from the reservoir itself. Once I had adjusted the pipes to the proportioning valve I then fitted the MC to the booster via the two bolts. At this point it was time to bend the rear connections a little to fit the smaller pipe at the front pot. The other side of the regulator valve was also coiled to allow movement and look nicer. The photo’s don’t really do the job justice as the pipes look a mess. But when seen they look like a miniature roller coaster. The rear larger pot was then attached to the front pipe feed and screwed firmly into place. The other end attaches to the front regulator valve. Last but not least was the vacuum hose, this was cut to length from the back of the engine to the valve on the booster. I used jubilee clips here, but I may change these to look nicer at a later date.


Believe it or not there wasn’t many. The main issue I had been the lack of pipe to the rear section to make it look neat and not go near the exhaust pipes. So I had to replace that pipe. The worst job for me was the brackets, these were the correct size as it all fitted perfectly, but for me and my big hands it was a real headache and painstaking to complete. These four nuts took more time than fitting the rear brake line. The position of the locking pin on the pedal is a fun to get at. Big hands small spaces don’t make for pretty listening outside the garage!


The look is brilliant. I just love it. The safety factor is obviously a major plus. Will it work? I don’t see why not. I just have to make sure all the connections are done up tight!


This took me around ten hours. Yes its a long time but ~I did things pretty with the coils, I had to go out and get more pipe I had to make new flares for the pipes etc. difficulty was more awkward than anything. I enjoyed the who process. Now I have a ’66 with a 67 dual MC kit!

Thanks Adam for the advice and all the little bits I needed to complete the job.

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2 thoughts on “Master Cylinder Upgrade To Dual Reservoir System

  1. Thanks for this great tutorial. I just changed my 64.5 to a dual master cylinder but couldn’t figure out how to get the brake pedal back together! Thanks for your great pix! Great blog also.

    New Mexico, USA

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