39-48 Rear Wheel Cylinder Problem

[Tom Smith]

First to let all know that I have not worked on this vintage of brakes until now. I was asked to replace the rear wheel cylinders since I had the drums off checking the condition of the shoes. The front cylinders were replaced before, the rears were not. I replaced them with new that I was given. After starting to bleed the lines I found that the right cyl. was leaking on the front side. The left side had a small leak, not sure were it coming from. I made the decision to purchase a new set of cylinders, thinking that I did something wrong or there was a problem with them. I installed them today. I took my time making sure everything was done properly. Started the Bleeding of the brakes on the right rear, same problem again with a larger leak of fluid. Please HELP! What I'm doing wrong?

[V12Bill]

How would you know where the leak is unless you had the drum off of the car. Clean up the brake fluid, especially off the brake shoes and start over. This time put the drum on the axle to keep the fluid from pushing the piston out.

[Tom Smith]

Both times all drums were installed while attempting to bleed the lines. It was found both times after removing the drum, it was leaking from the front side of the cylinder.

[Kurt in NJ]

Have you taken the cyls apart, it is possible that there are metal shavings stuck in the rubbers( I have had leaks from this on brass sleeved rebuilds), the rubbers were never good, the machining could also be a problem--I went through this problem on my 46, and 39, now just have the model A ,and 36 because the reliable safe mechanical brakes don't have leakage problems

[Henry/Kokomo]

Tom - The drums were on but were the shoes adjusted? If there's too much gap between the shoe and the drum you could be pushing the cylinder(s) too far. Just a thought. Good luck.

[Tom Smith]

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Kurt, Both cylinders were new when installed. I love driving my A also.

[Tom Smith]

Henry, Thanks for your suggestion, might be possible. I will check to see if I reset the lower adjusters.

[hardtimes]

Originally Posted by Tom Smith

Henry, Thanks for your suggestion, might be possible. I will check to see if I reset the lower adjusters.

Hey Tom,
First question...are the whl cyls made in USA or china?
You say that you checked the shoes, so I take that to mean that you made sure decent or new shoes/lining? If so, I don't see any way (with drum on) that you could have a situation where a cyl would leak from being pushed out tooo far, IMO. Before I would disassemble any cyl, I'd make certain that the fluid line is not leaking slightly..mine had to be scarey tight to stop a nuisance leak....that went down the back of cyl and looked to be coming from bottom of the end of cyl! Are you installing dot 3 or synthetic fluid?

[Matt in Alameda]

You do the upper Nuts with the springs first to adjust the brakes, the lower two oblong tabs are for fine tuning..ie; centering the shoes. Start out with the dots facing each other. I buy only from Richard Lacy in Los Angeles as he has American made parts. His # is 626-338-2282 More expensive, but stress free afterwards. Good luck,....Matt in Alameda

[cmbrucew]

Tom
Did you remove the cups and inspect the cylinder bores before installing?
I have found dry bores and scratched cup in the new boxes.
Recomend cleaning them good with brake fluid and checking the cups with good light for scratches. Also reuse original bleeder valves instead fo the metric hex on the new ones.
X2 on Hardtimes advise.

Bruce

Works good
Lasts long time

[john worden]

Last week I found a flawed rubber cup in a new cylinder assembly. Leaked. Replaced it with one from NAPA.

[Mart]

Stop!

I know the answer to this.

It is nothing to do with shoes or adjustment or anything other than the new cylinders being sold today.

I had the same problem.

here is an older cylinder - ignore the corrosion - it's the position of the two drillings in the bore that is important.



Note the position of the two drillings in a recently supplied rear wheel cylinder.


The new cylinders are made wrong and are DANGEROUS. The feed hole is drilled so far up the bore it is no longer behind the seal.

I took the problem up with Macs and gave up after a while - trying to convince someone they have a problem from 3000 miles away is difficult.

A UK supplier supplied me with new wheel cylinders and they were the same.

I ended up using the pistons and seals from one of the new cylinders in the best pair of older castings I could find.

These suppliers need a massive backlash of complaint over this, the situation is not just one of shoddy parts but this is a safety critical part in a system that is normally single circuit.

Don't want to put Dick S. on the spot but, as a supplier, maybe he knows of a source for cylinders that are drilled properly.

Mart.

[Tom Smith]

Mart from England, You are 100% correct. This is what 2 suppliers are selling. I was told today by the manufacturer to take 1/8" off the contact point of the shoe to compensate for the position to the fill hole. Not only the angle of the supply hole is wrong, but also the hole size is different from the left and right. Not sure how vendors are not getting complaints.

Tom

[Bluebell]

Good post Mart.
I wouldnt be altering anything else in my brakes. Those new cylinders are just not suitable, and should be refunded or replaced. Otherwise, I would do what Mart did and have some originals re sleeved (while watching for all the faults possible while going down that track)

[Terry,OH]

I just replaced a LR wheel cyl on 46-8 brake system, it was leaking from the front (larger) piston. It was one year old and USA made. The vendor stood behind the cylinder and sent me another no charge.

[deuce_roadster]

I had the very same problem with new cylinders, after troubleshooting it, found the pistons/seals were being pushed too far back of the larger bore (or the hole was too far from the center of the cyl) and the edge of the seal was slightly past the hole. My solution was to grind about 1/16th inch from the tang on the end of the shoe where it contacts the piston,re assemble the cylinders pushing the piston/seal back out where it belonged--problem solved. My drums had been turned and shoes arced to them, everything new so I wanted to fix what I had. That was my "backyard" solution--everything worked fine after making sure the piston didn't go too far in. I first thought that the lining was too thick. It was shocking to see fluid coming out of the drums when everything was new. This was all on a 40 Ford.

[hardtimes]

Originally Posted by Tom Smith

Mart from England, You are 100% correct. This is what 2 suppliers are selling. I was told today by the manufacturer to take 1/8" off the contact point of the shoe to compensate for the position to the fill hole. Not only the angle of the supply hole is wrong, but also the hole size is different from the left and right. Not sure how vendors are not getting complaints.

Tom

Earlier I asked if you were using USA or other...no answer? I take it now from your input here ...that you used off shore cyls...no?
Anyway, my point was ..if you still have USA old cyls...REBUILD them! Check the archives and you will find pictures of what look to be really bad USA cyls that I rebuilt..with success! These cyls sat in vehicle for 15 yrs unused, however they were real deal USA stock and work well now..I used advice that I'm giving you here, that I got from the guys here, when I asked whether to use offshore junk or USA made . Your choice, good luck.

[Fe26]

...'told to take 1/8th" off the contact point by the manufacturer'

That is a Bull#hit solution and insulting, and should be rejected outright. Try telling that one to a Judge.

This is serious stuff; knowingly altering a good part to remedy a defective part in the hope/attempt to make it work could leave you wide open to...

Unless the manufacturer or supplier can supply you with an Information Bulletin approved by your State or Federal authorities you will not be acting in accordance with approved protocols for motor vehicle braking systems.

My advice would be don't do it. Return the parts as defective and have the originals resleeved, this is a safe proven method of brake repair.

[PeteVS]

I would recommend that if you have old cylinders re-sleeved, ask the people doing the work to not redrill the feed and bleed holes. I had some done and I think the outfit had a ten year old drill the bleed holes with a hand held Makita. The cylinders came back to me with the bleed ports egg shaped. I had to make a drill guide and redrill them larger, but round.

[Marv]

I think we better hold on to our old American wheel cylinders and have them sleeved with stainless steel. I would think they would never need to be done again. Marv