Thread: Cleaning RR brake fluid reservoir

I started to work on the master cylinder but when I pulled off the reservoir it looked loke it was coated with mud on the inside. Almost impossible to see ant fluid levels. Warm water and detergent went a long way but mechanical assistance (like the end of my little finger) was required to get the final dirty film off but was only possible in the part under the filler cap.

The second part of the reservoir is separated by a fence open close to the top. The only way into this area is through the pipe at the bottom which plugs into the MC. No amount of swishing with water would move the film, mechanical assistance is required.

I got a small length of soft garden tie and cut it down the middle. Then I poked on end into the reservoir and put a big knot at the other end so it could not get inside. With some water and detergent I shook the reservoir in all different ways, trying to get the tie to run against the walls.

And it works! Not perfect but now the fluid levels will be clearly visible.

While I was doing this I asked myself how air got in as brake fluid was sucked out? I found two tiny (~0.6 mm dia) in the top of the cap. Investigation showed these were not as clear as I thought they should be so I pulled off the top of the cap and redrilled them. Now there is ample replacement air into the reservoir. With the cap off it takes about 6 seconds for a full load of water to drain through the MC connections. With the cap on this increases to about 12 seconds. Previously it barely flowed.

Now I am wondering hat is further downstream in the brake lines and calipers?

I hope someone finds this useful.

Cheers

Graeme
Pics anyone?

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You did well being able to squirt it into all the nooks and crannies.