Brake Master Cylinder Refurb, Again.

Had an issue with the Corsair’s brakes again, they were locking up as I found out after a short run (less than a mile) last Sunday. So I posed a question on a favourite Facebook group and most of the helpful answers came up with the master cylinder being the likely cause or to at least start at the top of the hydraulic system. I checked my (this) blog to see when the master cylinder was last refurbished and I was surprised to see it was October 2012! I had nothing to lose by investigating because the first thing I noticed when I drove the Corsair out of the garage was that the front calipers were seized on.

With the front jacked up, I released the brake pressure from the front offside caliper and the wheels moved freely. A pump on the brake pedal and the brakes seized on again. I released the pressure this time from the master cylinder output and the front wheels rotated again. Looking into the reservoir, the fluid did look a bit cloudy and with what appeared to be black flecks of dirt in the bottom. It was then that I decided to remove the brake master cylinder, so I pumped out the brake fluid via the off side front caliper to reduce the chance of spillage of brake fluid or making a mess during removal.

Ford Corsair V4 master brake cylinder
Ford Corsair V4 master brake cylinder – partway through re-assembly, note old components bottom left

The exterior of the master cylinder was in a reasonable condition, having only really covered about 3,000 miles since 2017, but in the now empty reservoir there was a fair amount of sediment in the bottom. Removal of the master cylinder wasn’t too much of a pain and it was on my bench in about 5 minutes. The plunger seemed to operate well but I was more concerned with seeing the condition of the seals and cylinder bore. Using a technique of compressing and letting the spring inside the master cylinder bore push enough of the plunger head out to be exposed that I could extract it with long nose pliers. Upon inspection the seals and cylinder bore were quite dirty but looked ok. I flushed it with old brake fluid a few times, then rinsed the reservoir and bore in some old petrol before another flush with brake fluid and a good wipe out with a soft cloth. To my surprise I happened to find a new Burton Power master cylinder repair kit on the shelf so I could replace all the seals, a spring washer, plunger retainer clip and rubber cap gasket. Another clean up of the master cylinder exterior body and the lid contacts and it was ready for reassembly.

Ford Corsair V4 master brake cylinder
Ford Corsair V4 master brake cylinder – 7/8″ bore looking clean

With the repair kit came some special brake cylinder grease, which I didn’t have the last time I refurbished the master cylinder, so I made use of it this time. Re-fitting the master cylinder back on to the bulkhead and re-attaching the brake pedal plunger rod all went without any problems. Then using the offside caliper as the main bleed point I duly topped up the reservoir and gently pumped the pedal until fresh fluid came through the brake caliper bleed nipple. After tightening the bleed nipple off, I had a bit of spongy pedal with good pressure and effective brakes.

Ford Corsair V4 master brake cylinder
Ford Corsair V4 master brake cylinder – prior to refitting

A short test drive, with the dog, produced good enough results that all was well and the Corsair would be ready for a decent run when the lock-down ends. More online orders arrived this week, which were Superflex poly bushes from Burton Power and I was just awaiting for the steering ball joint repair kits, to arrive from Amsteer. That should nearly complete everything required to refurbish many parts of the front suspension. I felt it made sense to replace all the other affected parts that looked worse for wear as removing the front struts would give access to these worn components.

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