Any Ideas? New Brake Cylinder Leaking!

This is a strange one. Any ideas would be appreciated. My '29 Hot Rod I just purchased had weeping front brake cylinders and worn out hoses. Front brakes are the 1940-1941 type with the adjustable lower attachment points (yeah I hate them too). I replaced the wheel cylinders with brand new ones from C&G Ford Parts in Escondido, CA. They both leaked badly, from the start. Didn't even get a chance to bleed them. So I call C&G and they say someone else had problems, so they are changing to a USA supplier. They sent me a new pair pronto. Installed the second set, and the Driver's side still leaks like a water faucet. So next I buy another cylinder, also USA made, from a different supplier at Vintage Ford Parts in Anaheim Hills. I install that cylinder, and it flows out like a river, just as the other did. I've tried aligning the shoes to the piston by tweaking the attachment clips (pistons on the new units have a uselessly wide groove in them by the way), I switched fluid brands (Dot 3), I honed one cylinder, all with zero luck. The thing still leaks like crazy. I'm wondering if the NOS '41 Drums could be bell mouthed and causing the shoes to tilt, putting a side load on the piston? I've noted that the USA made pistons are fairly snug in the cylinders. Not much slop. Could the FORD shoes be bent? The shoes look newly rebuilt, but they could be bent I suppose. Anybody else had this problem and figured it out? This has everyone stumped including two professional mechanics. Thank you! -Jerry:>)

 

I performed a simple test tonight. I removed the drum & shoes, then carefully put a clamp across the two opposing pistons. When I stepped on the brake pedal, NO LEAKING. So now I'm certain it has to be something to do with the interaction of the drum and the brake shoes. I'm taking the drums & shoes to a specialty shop tomorrow to have them turn both drums and check my brake shoes for any bends or twists. I'll let you know what I discover. Brake Safety is job one!

 

There's zero chance the pistons are simply pushing out too far in the bore?

 

You have a couple of choices here. If your over extending the travel due to the drum's being turned to much you need over size shoes. A measurement of the drum and shoe diameter is in order. Most brake shops have a measuring devise to check this. Having that many defective wheel cylinders is very unlikely but possible if they have had a long shelf life.

 

Thanks guys! The shoes combined with the NOS drums make for a very tight fit. I can barely get them on with the adjustment set to zero. So too much piston travel isn't the issue. Maybe too little piston travel? In looking at the offending drum, it certainly could use a turning. It's not all that perfect, just has alot of meat on it. Keep in mind that frequently NOS (New Old Stock) means that the part didn't fit well back in the day and was put back on the shelf. That goes for NOS chrome parts and trim too. So NOS isn't always the best part to use. I'll know more later today. I appreciate your ideas. -Jerry:>)

 

Jerry with the additional information on NOS It then has to go back to defective wheel cylinders due to sitting on shelf to long or wrong pistons or cups. If the rubbers are good and not groved from rust in the cylinder from long shelf life then its possible the piston is and has to be to small od.

 

MYSTERY SOLVED!!

To successfully work on an old car, you frequently need to be a Detective to investigate why things happen, or don’t happen.<O</O
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File this story under "Weird & Strange Brake Problems". My newly acquired Chevy powered '29 Ford Roadster had a leaky front wheel cylinder. Note that I’m I'm using regular brake fluid. Front brakes are 1940-1941 Ford units with the lousy adjustable lower pivots everybody hates. I had been fighting this leaky wheel cylinder problem for over a week. Here were the symptoms:<O</O
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1) I put a total of THREE new (not NOS) replacement wheel cylinders on the Driver's Side of the car. Each time it would leak fluid out of the large piston end of the wheel cylinder. Poured out in a stream down the backing plate. The other smaller diameter end was not leaking. Last two units were made in USA. Three different vendors. <O
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2) I thought it was the alignment of the brake shoe to the wheel cylinder piston, but after aligning it by adjusting the brake shoe retaining clip, it still leaked. <O
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3) The piston fit the cylinder very well. No side to side slop. The new old stock Ford drums fit very tight by the way, which I didn't like. It was hard to get the drum on over the near new shoes. I thought might have it turned anyways, because the way it dragged I knew it was out of round.<O
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4) There were no "expanders" inside any of the new wheel cylinders. Just a simple tapered coil spring.<O
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5) Stock '40-'41 FORD script shoes, with near new bonded brake linings. <O
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So what was causing the problem? It was a combination of the Driver's side drum being out of round, too thick (NOS) and the shoes not being arced to fit the drums. The seals in the pistons were too retracted inside the cylinder to expand and function. They just didn't have enough room. Turning the out of round drum on the lathe (three passes) and arcing the shoes gave the brake more adjustment space and allowed free spinning of the wheel. Such a simple thing solved the problem immediately.
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I highly recommend the brake services of C.H. Topping Co. in Long Beach, CA. Amazing vintage Brake Shop. They confirmed this scenario and says it happens once in awhile. In the end, I did have both front drums turned and both set of shoes arced for a perfect fit.


Now I'm redoing the rear brakes which were also a seeping mess! Replacing almost everything including new bearings. Had the drums turned and got new shoes. So far no strange mysteries!!<O</O

 

So, you're saying the 2 seals were touching eachother inside the wheel cyl? If not, then they should have worked as designed. The seal doesn't care/know "where" in the cylinder's bore it is

 

Good, logical & methodical approach! Sometimes you just have to leave it sit a while and think about it.

 

I had the same problem of leaking cylinder once. I had started bleeding the brakes before I adjusted the shoes out to their correct position. The spring pulled the shoes inward too much and forced the inner rubber cup in the cylinder to go past the fluid inlet hole in the cylinder. I adjusted the shoes to their correct position, and never had the problem again. I guess I'm just lucky (?) I didn't have NOS drums to contend with also.

 

I have no idea what kind of shit you guys are working on, but all the drum brake stuff I've worked on had STOPS to keep the shoes a certain "engineered" distance from everything else. Someone's using mix-matched parts (push pins that are too long or something)

 

Get yourself a set of 39-41 Ford brakes and you'll see of what we speak. Archaic stuff, but you gotta love it!

 

There's gotta be "stops" of some kind. Every drum brake should have "something" to limit the return travel of the shoes. The return springs return the shoes to those "stops" every time you let off the brake, or the chance of squashing the seals together every time would create some real safety issues

 

Yes, the stops are adjustable, and that is what I didn't adjust correctly before I got my leak. I figured out what was happening, adjusted the stops (those big bolts that show on the backside about 3 and 9 o'clock), and then no more leaky.

 

I'm gonna go out on a limb here, and say those are "adjusters", and NOT "stops". Stops are just that (STOPS), and would NOT be adjustable. Think about it before you retort

 

Alchemy and Tagman get it. Thank you guys! The Brake Shop knew immediately what the problem was, as they have seen it before. As a 37 year Senior Designer I had an inkling of what was going on, but just couldn't believe it either. I guess the main thing to remember that never start off with the adjustment so tight (compressed) that the pistons are both completely retracted into the cylinder. The only so-called stops are those two clips that retain the brake shoes. They hold the shoe in place, but do not keep the pistons/seals from being too compressed. As Alchemy mentions the inlet to the cylinder also plays a factor in all this, as when the pistons & seals are compressed, the bigger piston's seal sits right on top of the inlet. These old Ford Brakes are an animal to be respected! I hope this tale helps someone out there, as it had a bunch of gearheads, pro and shadetree, stumped for well over a week.