69FASTFUN

I have an original GM master cylinder for power brakes that has the bleeders on it and I would like to rebuild it. I took the piston out to clean the inside, is there anything that I have to do to the bore like hone. I can not feel any ridges. What should I use to clean to make sure I get all of the dirt and grime out.

Thanks

Scottd

Is it REALLY worth the effort? You can get rebuilds for less than 30 bucks. You time alone will cost you more.

As for cleaning, most car stores sell gallon buckets of carb cleaner.....dip it for a day, clean it off and it looks good as new.

If you are going to hone, (and dont have the proper stone setup) go in with some 120 sandpaper and hit it until it looks scratchy yet smooth.

Steve2147

Wash it out thoroughly with hot soapy water. The bore is not like an engine cyl bore, you will not find a wear ridge. What ruins the bores is pitting where the crud was sitting.

Honing the cyl is not like honing an engine cyl either. We leave a cross hatch visible scratch in an engine to aid in seating the rings. In a brake cyl we have a rubber seal sliding in the cyl. We do not want, nor need, to see visible scratches. 120 stone would be okay for a first run to clean the hard crud out, but you want to finish with a 240 or higher grit.

If your bore was perfectly clean and smooth end to end after cleaning, there is no need to hone. Examine it thoroughly for pitting and if there is none, you're good to go.

Assemble with your new kit using brake fluid to lube the parts as you assemble.

Steve g

69FASTFUN

I know I can buy a remanufactured master cylinder but the one I have is original and has the side bleeders wheer the remans do not.

redvetracr

you might consider sending it to a place like White Post or maybe Lonestar and having them sleeve it.

7T1vette

Clean the part well. If you want to polish the valve bore, fly-lap it with some emery cloth with a few drops of oil. Then, clean it out again. If any of the lands in the valve bore are scratched beyond polishing, are pitted, or are otherwise damaged replace the master cylinder.

Alan 71

Hi 69,
I agree that it's nice to keep the original part if it's usable the way it is, or restorable. There is a reproduction that's VERY close to the originals.
The original m/cyl on my 71 was pretty cruddy in the bore where the seals sat but cleaned up well enough that I couldn't feel any mark with my finger, so I put new pistons and seals in it .... so far so good.
Good Luck!
Regards,
Alan

Steve2147

I was taught to never lube with anything petroleum based when honing brake components. Brake fluid has been all we've ever used.


Wash extremely well if you've introduced oil.

Steve g

7T1vette

OK. Use a few drops of brake fluid, if that makes you feel better. You still have to clean all the polishing debris out of the M/C, so what you use for lube doesn't really matter.

Steve2147

Interesting. I wonder why all the car manufacturers in their fsm's and brake part manufacturers in their instruction sheet packaged with their parts always tell you to never introduce oil or solvent into the cyl? In fact Chrysler says to never even wash brake hyd parts with anything but brake fluid. Old school thinking?

You gotta love the Internet. Great source of the most up to date and complete information.

Steve g

noonie

If you want to save the original casting that ends up with a pitted bore, there are a few places that will sleeve them in either brass or stainless. Forever fix, after that, only the seals and pistons will ever have to be replaced, no more pitting.

Over the years, I've cleaned master and wheel cylinders with everything imaginable, acid, gasoline, diesel, carb cleaner, brake cleaner, brake fluid, degreaser etc with never a problem.
Final flush was always with brake fluid.

muskegonbrake

If you are interested in stainless steel sleeving let me know.

Andrew
800-442-0335
http://www.muskegonbrake.com