Cleaning brake master cylinder?

[living_the_dream]

I'm redoing my brakes and I got the reservoir for the master cylinder off and drained and the bottom is full of junk and grime. It's not accessible to clean by sticking something in there and wiping it out so I was wondering what's the best way of cleaning this. Any ideas? Thanks!

[DMCMW Dave]

Aerosol brake cleaner. If your wife isn't looking, run it through the dishwasher.

[David T]

If the reservoir is that bad you can figure the junk got into the master cylinder and the bore is also corroded. Figure on rebuilding the master if it isn't very badly pitted and if it is you need to exchange it for a new or rebuilt one. And if the master is bad pretty soon the calipers will start leaking so you should figure on and budget for a complete brake system (and clutch hydraulics if your car is a 5-speed).
David Teitelbaum

[living_the_dream]

Dave, so would it be OK to take some soapy water and pour it in there and shake it around to clean it out? I've got a new master cylinder from DMCH that I'm installing and I also have Martin's stainless brake lines. I've got a bleeder kit as well so I can flush everything out of the lines because it is pretty dirty. I hope all of this will suffice.

[DMCMW Dave]

Sure - just get it DRY before you put it back on the car. There are a lot of blocked-in cavities so setting it out in the sun for a while before you install it helps. Or lots of compressed air.

[David T]

Instead of soapy water I would use alcohol.
David Teitelbaum

[Mark D]

Resurrecting this old thread...

My brake master reservoir was filthy and no amount of brake cleaner spray, soapy water, alcohol, or fresh brake fluid would clean away the rusty layer of film coating the inside.

I finally figured out a great way to get it clean and here is what I did:

First I plugged off the two holes at the bottom of the reservoir and sprayed some aerosol brake cleaner inside. Then I dumped in about 50-100 small stainless washers. I cupped my hand with a towel over the opening of the reservoir and shook it around so the washers scrubbed the inside clean. The friction of the washers got the inside spotless, and when I was done all I had to do was rinse out the reservoir one last time.

You wouldn't need to use washers... ball bearings, small nuts, screws, or even small plastic beads would work.

[Delorean Industries]

Dish washer is the best way. DO NOT put it on the bottom. Same reason for Tupperware it will melt and distort due to the heat. Also make sure that the setting for "heat dry" is off. Go to the parts store and buy a pack of vacuum caps and plug the two small holes in the bottom. Sit it on the top shelf and fill it with vinegar. Run it through a heavy wash cycle and you will be surprised.

This is what we do here at DPI. We actually have a rolling whirlpool unit I yanked off craigslist just for this.

[David T]

If it is REALLY bad inside it is very hard to clean all of the tiny passages and ports. even with some kind of media tumbling around inside. You would have to remove all of the external lugs and try to clean the passages and then plug the external holes. Not worth the trouble. Replace the master if it is that bad. When it is that bad even if you an get it all clean and shiny, the main bore will be pitted and eventually tear up the seals on the piston.
David Teitelbaum

[Mark D]

If it is REALLY bad inside it is very hard to clean all of the tiny passages and ports. even with some kind of media tumbling around inside. You would have to remove all of the external lugs and try to clean the passages and then plug the external holes. Not worth the trouble. Replace the master if it is that bad. When it is that bad even if you an get it all clean and shiny, the main bore will be pitted and eventually tear up the seals on the piston.
David Teitelbaum

I was just referring to the plastic reservoir, and not the master cylinder itself. You're correct though about replacing the master cyl if it's full of crap. I doubt it is worth trying to rebuild since replacements are so readily available.

No need to buy a new reservoir though if it can easily be cleaned and reused. The dishwasher idea sounds like it works well too.

[David T]

You can wipe out the reservoir pretty well with alcohol and some long Q tips. The dishwasher tip should work well with the hot water. Dry it well and it wouldn't hurt to rinse it with alcohol too to make sure there is no trace of any water inside.
David Teitelbaum