Tuesday, September 29, 2015

New Brake Limiter Valve

Having spent the last year building and fitting a new engine in the Mini, there's just one last job that stands between me and my first trip out, and that's to bleed the brakes. There is just one snag though, there's almost no fluid coming out at the rear bleed valves!!

Bleeding the brakes should be an easy enough affair, connect the brake bleed kit, open the bleed valves and watch the bubbles escape. That wasn't to be the case though, starting at the rear, there was virtually no fluid bleeding from the bleed valves.

I checked the front's and they were flowing perfectly.

I was a little worried that the brake master cylinder was knackered and as it was such a pain to fit, the thought of having to take it out again was not a happy one. Before panicking though, I decided to take a logical step by step approach to try and trace the problem and just hope that it wasn't the master cylinder.

Removing the lower brake pipe that came out of the brake limiter valve, I placed a pot underneath to catch any fluid and pressurised the system with the bleed kit. I was expecting a flow of fluid, but there was nothing, not a drip!

Next I removed the brake limiter valve entirely and placed the pot beneath the rear brake pipe and pressurised the system again. This time to my relief, some fluid came flowing out. To double check, I pressed the brake pedal which squeezed more fluid from the pipe into the pot. Phew, it wasn't the master cylinder at least!!

What it was though, was a blockage in the brake limiter valve that I'd spend to much time cleaning up in this post here. Cleaning all the brake fluid from the outside, I confirmed it was blocked by pursing my lips and trying to blow through the rear inlet hole and sure enough, it wasn't possible.

After doing a little research, I found that inside there was a ball bearing that forms part of the mechanism that reduces the pressure and for some reason it had become jammed. Unfortunately, the brake limiter valve is a non-serviceable part so a new item had to be purchased from Mini Spares.

Once it arrived it took about half an hour to fit...

... and once fitted, the system was pressurised again with the bleed kit and this time the rear valves were now thankfully bleeding properly. Going around the car, I bled the system several times until I was sure that all the bubbles were out of the system and this was confirmed by a nice solid feel when the brake pedal was pressed.

So that's it, the last job is now complete and the car can now be driven. Alas though, I've finished the work too late tonight to go out, so I'll have to wait until another day which is a little disappointing, but in another way makes it more of an event.

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