I have a a wheel cylinder that leaks. Sounds easy? This has been a problem for over a year. I cant take it any longer. I have replaced the wheel cylinder with a new one three times. Two of them were made in india. One was made in america. Replaced the seals in them at least four times. THE SET UP: 39-48 ford wheel cylinders, Buick drums, 3/16 brake line, master cylinder from speedway, they say it is a 1" bore. THE PROBLEM: The drivers side wheel cylinder leaks out of the 1 3/8 seal. After bleeding the brakes. I take the drivers side hub off. Lift the dust cover on the wheel cylinder and brake fluid dumps out. I have used this exact brake set up on several hot rods and never had a problem. HELP!!!
We just went through this on a friends 34 Ford with the same brakes.. Multiple new 'import' wheel cylinder's, every one leaked just like you described.... We were fortunate to have a friend with a box of NOS wheel cylinder's from years ago, all in excellent shape....we scrounged two and installed them and they worked perfect... One thing we noticed with the import one's was when we adjusted the brakes that's when they leaked..olmost as if the tolerances toward the outside of the cylinder body were not so close..before adjusting, although you had to give two pump's, it didn't leak because the piston's went further back in the body when released. We were going to rebuild the one's that came off if we couldn't find a new one to work, is that an option for you? Tony
Have you looked for NOS wheel cylinders? Just got two and saved money at Antique Auto Supply. I don't have the number here, but do a search here, there's a good thread on them.
WOW could that be true. No one makes a wheel cylinder that works. I can believe anything these days. The "made in india" wheel cylinder had strange looking seals that leaked so I replaced them with USA seals. That still leaked. The "made in USA" wheel cylinder" From napa auto parts leaks just the same. How could you manufacture a product that doesn't even work? So NOS is the only way to go? The bore size on these cylinder has been 1 3/8 when I looked up the specks in an old manuel from the 40's they said the bore size stock was 1/4. Any one know anything about that?
try taking the seals out of the cylinder and soak them in trans fluid for a bit. I did it befor and it worked good. The fluid swells the seals a bit and you may not have a leak afterwards.
Before you put ANY fluid pressure to the cylinder, adjust the shoes out to pretty close to the drum. Don't need to get them exact, just need the spring pressure off the cylinder. I had one that leaked past the cups because the shoe retractor spring pulled the shoes/links/cups too far inward and the fluid intake hole leaked past the sealing edge of the rubber cup.
In my past experience, use caution when using this practice. The chemicials in the trans fluid that cause the seals to swell are not present in the brake fluid. The seals will return to their normal shape after a period of time and begin to leak. I have had the same problem in the past with improperly made wheel cylinders (for o/t aircraft tug). After multiple bad ones from a off-brand supplier we bought one at NAPA and it fixed the issue. I found differences of up to .040 from cylinder to cylinder. If it was me I would rebuild some old ones and even re-sleeved if they needed it.
Well let's see...Yugos, Fiats, Pintos, Lucas Electronics... Man, this is too easy! Like catchin' fish in a barrel. I like the sound of alchemy's theory. And if you have some small enough bore gauges check the inside of the cylinders for taper. Maybe a slightly longer or shorter wheel cylinder push rod, if such a thing exists.
Never thought of that one. Makes sense. I don't think that is my problem the brake shoes are adjusted nice and tight to the drum.
Looking at the pic, it looks as if the left side is constantly activated and the brake has pulled the seal away from the body of the cylinder. I've not used that set up before so I'd say you have to adjust the brakes out further.
Good idea. There are no push rods on 40 ford brakes. they go directly to the brake shoe. So I could try a different brake shoe and see if it puts the seal in a different position.
The problem with "reverse engineering" is not knowing the tolerance ranges of the components. This is usually the culprit with defective parts.
I started looking through some old stuff and I found an original wheel cylinder. It is a little ruff but it might be savable. It is worth a try.
Antique Auto 1224 Colorado Ln. Arlington, Tx 76015 817-275-2381 He is at the DFW swap meet this weelend. Call next week.
Ok, since I sell wheel cylinders and have heard this story before let me interject what I have experienced. After air pressure checking so called defective cylinders I have not been able to determine that these cylinders are defective in manufacturer. What I have discovered is, that in comparison with the older manufactured parts and the new manufactured part there is a lack of adequate piston and cup washer lubrication. The newer production parts seem to be ***embled much drier than the older versions. It is my perspective that this dry ***embly leads to the cup lips dragging or failing to seal and allowing the cylinder to leak small amounts of brake fluid. Because this seal is not complete and the travel is so small the cup seal edge does not immediately return to its correct position and the minor leak continues until every thing gets a good coat of fluid, the cup edge folds back in place and the seal functions correctly. Now I have talked to one of the engineers at the cylinder manufacturer about this dry condition but as in every instance when the chain of command is involved, it gets slowed down, so what ever comes out of this I don't know. My suggestion is to check upon installation of wheel cylinders that the bores are adequately lubed with clean brake fluid. This can be workbench done by removing one or both piston cover seals, popping one or both pistons and seals , liberally coating them with clean fresh brake fluid and correctly re***embling them in the cylinder. Clean off excess fluids and then reinstall the piston cover boots. You can check the piston operation in hand by carefully pressing on the opposite side piston and feeling the other piston move slightly. One other note about leaky wheel cylinders hinges around the failure to install crush washers on may of the front hoses at the junction where the hose connection bottoms out on the wheel cylinder body. Many designs do not have the hose or line bottoming out on a inverted flare and this lack of sealing washer produces a leak or ingests air to produce a soft brake effect. You might really not have a leak at the piston, its a leak at the fitting.
Double check that your Master cylinder matches your wheel cylinder requirements, what the box says isn't always what's inside. If it's too big, it could be that wheel cylinder being closest, and being that it theoritically recieves the more pressure, may be falling victim
That is some good info. I am pretty sure that the leak is at the seal instead of the crush washer. After pumping the air out of the brakes I take the drum off and lift the dust cover off of the cylinder. As soon as I do that brake fluid dumps out of the wheel cylinder.
sck racing That is some good info. As far as the theory of my alinement or out of balance wheels being the culprit this problem starts before I even drive the car. As far as spring rate goes I have a handful of springs. I could try a few different ones out and see if it makes a difference. Is it possible that the master cylinder is the problem? the stock one for 1940 ford is 1 1/6". mine is 1". They also say the stock wheel cylinder is 1 1/4. But the ones I have been getting are 1 3/8. Could it be the master cylinder is to hi pressure for the wheel cylinder?
What about the shoe and drum diameters. Sure you got matching parts? If not, the cylinder will over extend and blow out the piston. **** man you tried everything else!
I would do some measuring here. Install everything without the dust cap so you can mark how far the shoe is retracting the piston. Then take the cylinder apart and measure from the piston & cup to the inlet. Some cylinders were tapered a bit around the inlet, check for that as well.
Go back and take Hydralics 1&2 over. That is the whole idea behind hydralics equal pressure at all points in the system. With a given force on the brake pedal a large bore M/C will have a lower psi in the system than a M/C with a smaller bore.
39-41 used the 1&1/4 X 1 inch bore wheel cylinders 42-48 went to the bigger 1&3/8X1 bore combo to get a bit more braking force. Basic hydralics a smaller bore M/C will produce more line pressure with a given force on the pedal . That 1/16 won't make enough differnce to cause any problems , like maybe 10 lbs less pressure on the pedal to produce a given deacceraltion rate. The smaller M/C piston will have to move further to displace enough fluid to operate the wheel cylinders than the 1&1/16 would. Wheel alingment and tire balance with have NO effect on a leaking wheel cylinder. Stuipd question 1 what do the drums measure ? absoulte max 12.125. ? 2 you are putting the open end of the cups facing each other right? like this [ ] Find someone with the proper measuring equipment and see what the cylinders actual bore is ,would think it should not be over 1.385. This is not rocket sience ,there is either a defect in the parts or they are ***embled wrong -damaged on ***embly.
OK, If you have a leak at the wheel cylinder piston cover, the fluid has to leak from the piston cup seal. Now carefully remove the wheel cylinder from the line and the backing plate. Put down some clean shop towels on a table and carefully dis***emble the offending cylinder. Carefully note the position of all parts as you are going to have to re***emble them correctly. After you have removed the piston and the seal cups check the bore of the cylinder for any scores or rust marks. The bore should be perfectly shinny, now check the fluid puddle on the clean shop towel, there should be no rusty brake fluid or dirt particles. One problem with wheel cylinder leaks is contamination from dirt or rust particles when the cylinders are swapped or the master cylinder cover is removed. At this time check for cuts or nicks in the rubber piston seal cup lip edge this would be your source of a liquid leak, also look for a dirt particle stuck to the cup lip.. Now clean all parts with Brake clean, recoat the cylinder bore and all cups and pistons with a good coating of clean brake fluid and re ***emble the cylinder ***embly making sure the piston cup seals are in the correct orientation. Re install cylinder. You can check or pre bleed your cylinder with out replacing the drum by using a large c clamp to bridge clamp the pistons in position and prevent them from popping out of the cylinder. Apply a light peddle pressure to bleed the air from the cylinder. This will also show you if you have any leaks if you roll the piston seal boot back. If there are no leaks, releasing pedal pressure and removing the C clamp, you can now reinstall all brake parts, make sure they index correctly. If the new cylinder still leaks after this then there is an issue. To sckracing and and heep creep your suggestions will take a substantial and significant higher grade of ditchweed to be even considered plausible.
To sckracing and and heep creep your suggestions will take a substantial and significant higher grade of ditchweed to be even considered plausible.[/quote] **** : I agree fully !! LOL
That was it. the seal was to far in the wheel cylinder. the seal was on the bleeder hole. All I had to do was take the brake pad off. Then belt sand 3/16 off of the end of the brake pad where it contacted the plunger. This pulled the seal away from the bleeder hole. Thanks everyone for the input. I knew it had to be something simple. I even threw on the "made in india" wheel cylinder to see if works. Now leaks whatsoever. Brakes are tight.
VERY COOL! I will now go with this info in hand/mind to my buddy and see if we can't solve his past problem as well.. It would be great if something this simple work's for him too...Then i'll probably buy two of his wheel cylinder's off him considering he's not gonna use them now Thanks for letting us know. Tony
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