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Ford Cortina Brake Servo


GeofP
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Do you need the servo?  I got rid of the Sierra servo and master cylinder on mine, replacing it with just the master cylinder from a KA (it's a smaller diameter bore).  No problems stopping the car and a good pedal "feel".  I think there are quite a few RHs out there with KA master cylinders now.

Steve

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There is a good explanation of servo parameters in https://core.ac.uk/download/pdf/76945365.pdf chapter 3.2.3 Brake Vacuum Booster, but not much help in choosing one!  A suggestion is to take one from a car of similar weight - mine is about 650Kg although the original Cortina would have been heavier that that.

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I noticed that the brake lights were not working.  There is a normally closed push switch mounted behind the top of the brake pedal which opens as the pedal is depressed.  It was tight against the pedal lever.  I adjusted the position and found I had to move it back about 6mm before it worked correctly. It meant I had made the push rod between the pedal and brake servo too long.  As an experiment I shortened the push rod by 8mm to see what effect it had on the braking.  It was a transformation!  It is much easier to control the brake power. it is still sensitive but much less so.  I need to try the car on damp roads and get a second opinion, but hopefully I won’t need to look for another servo.

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On 9/24/2021 at 10:59 PM, sylvia.fry2 said:

As above , my wife can easily stop Florin with just a Ka master fitted. Pedal feel is great.

Thanks Foz and Sylvia.  I had tried the brakes without the servo (by disconnecting the vacuum) but found the pressure to be much to hard. I hadn't thought of using a different master cylinder and anyway didn't have any means to determine the one to choose.  It it would be in interesting exercise to find how to mount it to the brake pedal and re-plum the hydraulics and getting rid of the servo would give much more access room under the bonnet.  Could anyone provide details of how the master cylinder is mounted?

 

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I can send you some pictures of mine but my car is a 2B, using a Sierra pedal box, so I'm not sure if it's similar to yours, or not.  I fitted new rear wheel cylinders a few weeks ago and I don't think I've got all the air out so  I want to try bleeding them again later this week.  I can take some photos of the master cylinder while I'm at it, if it will help.

Steve

 

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Having driven the car a few times now and once in the rain yesterday going down a series of hills, I am pleased with the brake handling after reducing the length of the push rod.  No lock-ups and reasonable control.  It is more sensitive than before, but I am happy to stick with the set-up.

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I tried to take some photos of my master cylinder today but soon realised it isn't easy to show you anything useful with everything in place ! 

It bolts through the front of the sierra pedal box, (where the servo was) with a couple of new bolt holes.  I then had to make up a new pushrod and pipe it up.  I have attached a photo of it in position to give you an idea of how it's fitted.

I'm glad you're happy with your set up now and it's probably best not to let me confuse things !

All the best, Steve

Clutch.jpg

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