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About GeofP

  • Birthday 02/11/1951

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  • Full name
    Geof Parr

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  • Gender
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    Rake, Hampshire
  • Interests
    Robin Hood!
    Wife and family
    Electronics and Raspberry Pi.
    Playing in a brass band

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  1. Thanks for the photo Steve, at least I know where to come for more info if needed! Best regards Geof
  2. 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.
  3. 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?
  4. 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.
  5. 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.
  6. Thanks IanS. Any suggestions about how I choose from a breakers yard?
  7. Yes, that's what I told myself ......
  8. Well, I finished the conversion a couple of weeks ago. There was a great deal of measuring and trial fitting. The brackets were made from 2 thicknesses of 20 x 2mm mild steel bar plus some aluminium angle – this was to allow adjustment of the servo to the correct position and angle. The spacer was a sandwich of 5 pieces of 3mm aluminium. I lengthened the push rod from the brake pedal to servo with 2 pieces of 3mm flat mild steel plate, cut in a curve to match the Cortina one. I also had to reposition the clutch cable and radiator header tank and add a vacuum one-way valve. The set up worked but the servo is much too powerful. It only needs a slight touch on the brake pedal to cause the brakes to operate and a gentle push to lock them up. So, the car is drivable but a little scary. I thought that using a brake servo of the same physical size as the Cortina would give similar braking, however that is obviously wrong. Perhaps modern servos are more efficient and I will need one that is physically smaller than the Cortina. I plan to choose another and repeat the fitting process!
  9. Hi Bob. Yes, I had considered the Sierra, but the photos on eBay items show the brake pedal push rod to be different. In retrospect, that might have been easier to modify than what I am doing!
  10. The body of the Cortina master cylinder does fit the studs on the Mazda servo but the push rod coming out of the servo is too long. It protrudes about 0.6” whereas the Cortina one is about flush. I considered cutting it shorter but didn’t want to risk damaging the servo so decided to make a spacer between the 2 units. However, the studs on the servo would then be too short to hold both the spacer and master cylinder. So, the spacer will have new mounting studs for the master cylinder and I will mount the servo to the space at 90° using its own studs. Anyway, that’s the plan.
  11. Thanks Dave, but no luck there. On Wednesday I visited a car breakers yard that had over 300 cars on display for a help yourself spare parts service. I didn’t know that sort of place existed anymore! I spent a couple of hours looking through about 100 cars for a brake servo that had about the same diameter and depth as the Cortina one with a master cylinder of similar diameter and length with 2 outlets for the front brake lines and one for the rear. The best match was one on a Mazda Bongo van and the second best was the Mazda MX5. Unfortunately, the plastic reservoir for the hydraulic fluid on all the cars had been disposed of along with the fluid. However, I managed to find a complete unit on eBay and have ordered this. I will need to lengthen the push rod between brake pedal and servo and make a new bracket to mount it. Then, my plan is to see if the Cortina master cylinder fits the Mazda servo. If so, that will make that install a lot easier. Otherwise, it will be a case of re-routing the brake lines and possibly modifying the reservoir if it is too high for the bonnet. Then fingers crossed that the hydraulic ratio is close enough to make the brakes work.
  12. I lost the bid at £81 inc postage! Hen's teeth comes in mind...
  13. Thank you, but it will not fit. I have another in view but bidding is getting busy!
  14. My S7 is based on a 1981 2000cc Cortina Estate and was completed in 1995. The other day whilst driving I touched the brake lightly and the brakes came on full. Releasing the brake quickly released the brake. Whilst sitting stationary with the engine idling, gently pressing the brake causes the brakes to engage suddenly and the engine note changes suggesting air leaking back into the servo vacuum tube. If I disconnect the brake servo vacuum hose and drive without the servo assist, the brakes work without snatching but I would not be comfortable driving this car without a servo. My conclusion is that the seals in the brake servo have failed and a slight movement of the brake rod causes uncontrolled air to enter the servo, with the vacuum then pulling hard on the diaphragm to operate the brakes. The Haynes manual for the Cortina states the servo can not be serviced but is likely to last the life of the car. (40 years?) If there is a problem, obtain a replacement unit. As I have discovered in my internet searches, there does not seem to be a company offering a repair service or suitable direct replacement. Can anyone suggest a solution to this problem, perhaps an alternative I could use, ideally one that would take my master cylinder so I would not have to re-route the brake pipes. The Ford Fiesta looks a possibility, although the brake pedal rod looks shorter and I don’t know the dimensions of the master cylinder mounting and if my master cylinder push rod would be compatible. Perhaps someone might have an old Cortina brake servo in their garage that they could pass on to me. Thanks Geof
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