Smokin' Rear Brakes

[Mariposa Mike]

yes it was on the car but looked fairly new on the outside. As I look at the dirty brake lines down below it's possible it just had a good metal finish of some kind. Inside it had dirty fluid especially in the front reservoir. Cleaned it up and hand operated the piston to observe operation with clear fluid. The front two holes bubble but only one on the rear brake end does that. Also the fluid travelled very fast to the front when hand bleeding but I did not see fluid come out the rear fitting. Pulled the piston out which only gets you to the rear ports and I see both ports are open in the rear chamber. Got some more black sludge out but have not put the piston back in to see if it is operating now. Plan to do that in the AM. It was getting too hot to work anymore in the shop.

Either of your suggestions are possible. It would seem though that the brake booster rod is not the issue.

 

[Mariposa Mike]

Bench Tested the M/C this morning and do not get fluid coming out the rear brake line fitting and it might be leaking past the rear seal, which it was not before. Don't see any bubbles either when working it. So I believe the master is bad. But don't see why. Since this is not a stock unit does anyone know who to call to replace it? Maybe one of the sponsors/advertisers on this forum.

 

[Mariposa Mike]

Took some measurements since this not a stock M/C and looked on line at Summit. They had a tech video that mentions bore size and how it affects the braking. There are two bore sizes available for this car with what appears to be the correct push rod depth. 1/8" deeper but I should be able to adjust the push rod. 1.06 diameter bore. The other bore size available is .937. The current one is the larger size. What the tech line advises is that the larger bore does not mean better braking with less effort. It's just the opposite. Smaller bore+more pressure. Like for disc brake calipers. Since I am running 4 wheel drum I believe the larger bore was correct. And since my brakes have not operated correctly since I got the car last year I'm reasoning the larger bore is correct. The product is made by a company named Right Stuff. Called them as well and they suggested the one I was looking at. Shipping is coming from just across the border from CA so I hope to get the part before the holiday weekend.

Further to follow. In the meantime I will take a look at the front brakes and at least change the hoses.

 

[AR67GTX]

If I remember correctly the front bowl feeds the rear brakes and the rear bowl feeds the front. You can pop the front piston out by blocking the brake line port with a threaded plug and applying compressed air to the larger port in the front bowl. But use caution as much pressure will really pop it out along with some brake fluid.

 

[Mariposa Mike]

Now you have me guessing. This one is plumbed reverse of that and a local mechanic told me it is correct. I asked because it would seem the larger (rear) reservoir would be for the front brakes/rotors. It might be a good idea to call the tech people at Right Stuff. Edit: I just did that and the tech said on GM the front serves the front brakes but on MOPAR and Ford the front serves the rear. So you are correct and mine is set up the reverse of that. Thanks for posting that response.

 

[Mariposa Mike]

Update on where I am at on this project. This has now become a complete change of parts for the braking system. The front shoes are of the more modern type with the square holes. Just like the rears. When I pulled the drum from the right front I found the self adjusting cable had come off the shoe mount. Still hooked to the self adjuster lever so no damage from being loose. When I ordered another set of shoes O'Reillys reported a different number that the rears. Those turned out to be the newer type like what is on the car now. I've decided to either order the rears again or better yet install the correct asbestos shoes from a supplier on this forum. Did not previously know about him and sent a private message. Also bought another set of springs from NAPA for the fronts.

With the left front shoes off I saw that I cannot change the brake cylinder and hose w/o loosening the backing plate to gain tool clearance. Did that and found that the brake cylinder, like the rears, only had one piston working and the other mostly frozen up. That's now three out of four and I expect to see the same with last one. Put the old shoes back on and found that the self adjuster does not work well with the spring modification which is probably why the other wheel has the loose cable. Later after receiving the new M/C I bench bled that and if I have not mentioned it before, found the brakes lines had been installed incorrectly with the larger reservoir feeding the rear brakes so rerouted those lines. After checking/comparing the depth of the brake rod off the booster I found that I had to shorten the rod to get a little clearance between the rod and the piston. I set it at 1/8th" which I hope is correct.

I'm now waiting for a response from a supplier and more parts to finish this job. In the meantime have to replace the right front cylinder and hose. Which means backing off the mounting plate on the right front. A real PIA by the way.

I hope to be able to report replacing all these parts has given me great braking again. Without smoke!

 

[Mariposa Mike]

Another update with pictures of the front brake cylinders. Have both off and replaced. Posting a couple pictures of them showing the buildup on one end but not the other. All four looked like this. One piston in each moved but not the other. Judging by the amount of grease caked on the hoses and cylinders I suspect the previous owner or an incompetent mechanic changed this system to dual M/C and Dot 5 without flushing the lines (completely). The M/C is newer than the brake cylinders and the brake lining was almost new. We will never know for sure but it's going to be all new except for drums. The left front could probably use a new drum but those are all from Cheeena that I have found so far. Might be okay for a cruiser however I'm uncertain at this point. That's where the brake cylinders came from as well as the springs and the shoes from India. May just try the original drum and see how this works. Easy enough to replace if need be.

 

[ckessel]

WOW!