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Anyone bother rebuilding master cylinders?

J

JohnC

Veteran Member
Senior Member
Mine is prob near 25 years old and although I have no reason to think it’s bad, seems like it would be wise to rebuild or get a new one. I did a GM front disk swap and just bought a generic early 70s Chevelle MC with the single bail. Looks like this:
IMG_3502.jpeg

For the sake of appearance I’d like to powder coat it. Figure the dark gray I put on my brake calipers looks pretty good.

I figure I have to pull it apart anyway so I don’t melt the seals when I bake it.

Not sure what exact vehicle my MC is from and I know there are different bore diameters available. But shouldn’t be hard to disassemble and measure.

Other option which probably isn’t much difference in price is to just buy a new one, disassemble, powder coat and reassemble. Mines in good shape though and if rebuild Kits are decent, might as well reuse mine.

Any thoughts?

Amazon has kits like this:
IMG_3501.png
 
Also, plan to use silicone brake fluid mainly so I don’t have to worry about future spills damaging paint. Any downside to silicone?
 
"I had good brakes at 10, but nothing at 11!"
Camaro driver at Sears Point race track after hitting the wall at turn 12.
He got about 12' altitude and landed flat, on the other side of the wall.
Seems Silicone has a very sudden transition from good to boiling when pushed too hard.

If you are not racing it should be fine.
 
I think the point Richard was making is while under pressure and constant usage (pushing the brake pedal frequently) and outside temperatures above 32 degrees Celcius (about 90 degrees Fahrenheit) silicone can boil.
 
Normal brake fluid fades and lets you know its on the edge, silicon seems to go from good to gone very abruptly when pushed hard.
 
Master cylinder rebuilds are going the way of radiator core replacements, I am sure there are companies that do them but will be pricey. Good for you attempting to do it yourself.

From the factory I believe master cylinders were not coated. If powered coated will it affect the bore in the spacing between the MC and booster? I have tried cast grey paint, works well for a while.
 
I don't like silicone brake fluid,too many down sides. You have to make sure its not mixed with any of the remaining dot 3 so there's no problems just because of that.
Had to use it in a guys Audi I used a pressure bleeder so there was zero air in the lines and flushed the lines with denatured alcohol still the pedal was soft when braking which led to all kinds of complaints.
Finally had to flush it out with denatured alcohol (both car & pressure bleeder) then replace it with Dot4. After doing that the pedal came back to normal and the car stopped great.
 
Updated. Pulled out my MC yesterday and it had gotten kinda rusty on the outside and the gold (cad?) lid was a bit corroded. Just for curiosity sake I disassembled it and the bore was super clean so it would have been a good candidate for a rebuild.
However Amazon had a Dorman MC for $30 or the rebuild kit for $30. Seems like an easy decision.
 
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