1938 Dodge truck - wheel cylinders leaking

[this_is_greg]

Over the past year I have been having trouble with my wheel cylinders. They have been leaking on and off, and I don't know why. Usually it's just a few drops running down the inside of the tire (see picture). The last time it was a puddle under the tire. Thisis the second set of wheel cylinders I have installed. Both sets had this issue.

 

Last night I popped the rubber boot off the wheel cylinder and a small amount of brake fluid ran out. Has anyone else had this problem? How did you fix it? I wonder if I am missing something during the brake job to align something. It seems the brake shoe may not be pushing perpendicular on the piston. Would that cause a problem?

 

Frustrated in Wisconsin!!

 

Thanks,

     Greg 

[this_is_greg]

Also, is it the same wheel cylinder for all four wheels or does the left side have different wheel cylinders than the right side? I see wheel cylinders on eBay that state right rear, front left, etc.

 

Thanks in advance.

 

Greg

[jpage]

Apparently the rubber cups inside the cylinder are not sealing. There may be some cavitation or scuffing that has scored the cup walls and is causing the leaking. I would check the bore and the cups. If all the lines, cylinders or master cyl. were not changed there may have been some dirt caught in that cylinder causing the leak.

[this_is_greg]

28 minutes ago, jpage said:

Apparently the rubber cups inside the cylinder are not sealing. There may be some cavitation or scuffing that has scored the cup walls and is causing the leaking. I would check the bore and the cups. If all the lines, cylinders or master cyl. were not changed there may have been some dirt caught in that cylinder causing the leak.

Thanks jpage. I did have the original master cylinder sleeved and replaced the brake lines that looked bad on the outside, but didn't think they could have rust/contaminants on the inside.I guess running all new brakes lines will be the next thing to do.

[Alan Cutler]

I always hone out the inside of the cylinders, prior to installing the pistons and boots. Just a quick spin, to ensure a smooth surface, I've seen brand new cylinders in the box come with grooves... 

 

Buy a honing bit, attach it to your electric drill (you need the high RPM's) and add a little brake fluid for lubrication....If you don't want to use a drill and bit, some high grit sandpaper would work, although may not be as consistent on the surface.

 

Just something to try...good luck!

[Spinneyhill]

1. Are the cups new? If the brake cyl is slightly oversize, are the cups that size too? Oversize cups are required in an oversize cylinder.

2. Is the piston corroded? Mine are aluminium and corrode against steel (galvanic corrosion) and the gritty corrosion products under the cup lip result in a leak.

3. How often do you drive it?

 

When mine do that (when it is not driven for more than a few months), a clean-out is required. I remove the shoes and pistons, using a clamp to keep the cups in the cylinder (just to prevent brake fluid running everywhere and reduce the bleeding required). Clean up the piston. Push the cup on that end forward (just so the cup doesn't come out the other end) and clean the cylinder. Install the clean piston with some rubber grease (care is required to make sure the cups don't pop out of the cylinder). Do the other end. Install shoes etc. With luck, you won't need to bleed it or only minimal bleeding is required. This is a tiresome job I have done a few times.

 

No. 4 assumes the cylinders are pristine and the cups are new-ish, fit the cylinder and are in good condition (i.e. the lips are sharp all round).

[Guest 1935 Dodge Van]

Usually the reason they are stating right and left is because the cylinders are "stepped". That means the front and rear pistons are not the same size. So they are "handed" right and left. You seem to have done everything I would have done. The spring inside has to be centered on the rubber cup. You should "wet" the cylinder wall and cups,master or wheel, as you assemble them. The pistons should have their outside surfaced wetted as well. If everything is not wetted there is a possibility of "chipping" the rubber cup and it will leak forever. If everything seems to finally settle down,it's a good idea to apply the brakes at least once a month or sooner to keep the cylinders and rubbers wetted. If the rubber cups and cylinders go dry you can get the aforementioned chipping. I think our braking systems were meant to be used nearly every day and not left for long periods of time. This kept the cups and cylinder walls wet and everything slid smoothly and kept sealed.