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'79 midget brake master questions

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tweety

tweety

Jedi Trainee
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Gentlemen......

It seems that my brake master cylinder is shot. There's a little puddle of brake fluid on the floor directly under the brake pedal, with the tell tale drop dangling from the pedal itself. One side of the cup is pretty much full, the other was empty. After cleaning up the puddle, I pumped the brakes and got a good dribble from the pedal to the floor. I did take the car around the block, while the brake pedal was mushy, the car stopped normally.

So my questions:

1. Rebuild or replace the master? I'm assuming a rebuild would do it.

2. Can a novice handle the rebuild? I've done brakes before (changed pad/roters/shoes etc) and bled brakes lines but I've never messed with the master cylinder.

3. If a DIY re-build is iffy, how hard is it to remove the old MC and replace it with a new one?

I would love to tackle this myself for the learning experience, but I'm prepared to let my mechanic do it if necessary. ANY WORDS OF WISDOM WOULD BE GREATLY APPRECIATED.
 
Many will differ on the rebuild question. There is a retainer ring way, way, down in the bore that if you scratch the bore in your attempt to remove the retainer clip it damages the retainer clip. Some have successfully rebuilt and others simply replace as new. On Bugsy my '68 Sprite I replaced as new 9 years ago. After 10,000 or so miles I do notice a slight dampness to the brake pedal that I need to keep a check on fluid levels. The brake.clutch master seems to be the repeated main problem people have with this car and I'm sure it is mainly due to lack of use. Regular exercise is the key to keeping the seals from drying out and leaking.

Replacing is simple. Biggest issue is bleeding afterwards. Lots of tricks to get it done. Once done I've never had to rebleed clutch or brakes, knock on wood, since redoing 9 years ago. Many topics on this forum on brake and clutch bleeding.

Replace flex hoses 2 in front and 1 in rear. Rear one frequently collapses and no rear brakes. Replace rear wheel cylinders as well. Cheap insurance to making sure brakes are in tip top order.

Master cylinder is a couple of bolts, disconnect linkages, drain out old fluid which eats paint BTW, and bolt in new Dual MC. Again bleeding seems problematical, just takes time and patience.Have heard varying quality on reports of MC Rebuilds by those firms that advertise in the back of Class Car Magazines. I went with new parts. Others responding to this note will provide their experience in doing a rebuild.
 
I'm a pretty novice mechanic too. I've done 3 MC rebuilds on old cars all successfully, I say go for it. Research the tricks on tear down and rebuild and bleeding here. Get a $15 kit and have at it, worse case scenario you end up buying a new one and you've lost $15 but you've learned a lot. I think the hardest part on yours will be getting it apart but these guys have the tricks, something about melting out the clip instead of trying to remove it? If I'm thinking of right type MC. Mine is an older version and is easy to take apart and put together.

PS I agree on doing the three rubber hose sections and rear cylinders (they're easy to rebuild too but so cheap to buy I didn't bother). But if they don't leak at all let them go, I guess it depends on how old everything else is. I did rear cylinders, shoes, rear hose, MC rebuild and left the front calipers untouched as they looked and worked fine. Good news is brake parts are cheap. Unless you have a 3/4" bore MC like I do and want another, there aren't any! So rebuild was almost mandatory for me.
 
I vote rebuild - a kit is sooo much cheaper ($20 compared to $250) that even if it doesn't work you are not out that much but if it does (and it should you fine)

I did it and it is easy (if I can do it, it has to be)

here is the link with my instructions

https://tinyurl.com/9q8nl9

took a couple of hours
 
Rebuilding the 1500 master cylinder is a pain; I attempted it once. The two things that make it difficult are a nylon washer that usually becomes stuck in the bore, and I found (as others have) that you have to carefully drill holes in it and take it out in pieces. Secondly, there's a snap ring way down inside that needs an ultra-long set of snap ring pliers to remove and install safely without scratching the bore. Note that my 1500 workshop manual actually calls out a specific British Leyland tool just for that purpose. I found a replacement MC at Napa for $225, which was well worth it after spending a few days trying to dismantle the old one. The new one also came with the bleeder tubes to do the bench bleed on, so bleeding it was a snap.
 
I feel strongly that the way to remove the nylon washer is to cook it out with a plumber's torch. It takes a few minutes and there is NO chance of scraping the bore. I have done the job both ways. The drilling method is almost guaranteed to leave you with a scratched bore.
 
no quarrel here though drilling carefully was not a problem
 
Morris just uses it as an excuse to burn things :devilgrin:

Pat
 
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