Jump to content

Wheel Cylinders Leaking


tonybiel

Recommended Posts

I am doing a restoration on my 1951  B3C.  I have replaced all brake components including new master & wheel cylinders, steel lines, hoses, shoes and other items.  Installed drums.  While attempting to bleed the system, both front wheel cylinders leaking to the ground big time.  I have disassembled the front cylinders, inspected and recleaned 3 times.  Cylinder cups, pistons and springs are facing in the correct directions and were correctly assembled the first time I took them apart.  Never any signs of contamination.  I have been very careful all along about cleanliness.  The cylinders and seal cups look good, but in the last disassembly, out of frustration, I did a light hone and installed another new set of cups.  These are two piston step cylinders.  The larger piston on both definately leak and not sure if the smaller pistons will leak under pressure after bleeding.   Measuring with a dial caliper, the cylinders and cups appear correct.  Using Dot 3 fluid.  Rear single piston cylinders seem OK.  Worked in a shop back in the 60's.  Rebuilt quite a few cylinders back then and don't recall ever an issue like this before.  Maybe someone else has.  Any suggestions appreciated.

Link to comment
Share on other sites

Kinda sounds like them bores might be out of tolerance for the seals to work, or the seals are out of tolerance inside the bores...might not hurt to contact vendor about replacement of defective parts...I've seen bores that upon really close examination were machined corkscrew-like, which was hard to detect but leaked like a sieve...

Link to comment
Share on other sites

Modern chinese cylinders can be .010" too big....you need to mic them. Piston to wall clearance I think is a max of .003".

Many original type cylinders used a flared thin washer in front of the return spring that helped push the piston cup lips out tight to the cylinder wall too.

Replacement parts today are questionable sad to say.

One other thing I've had happen is the pistons and cups being pushed too deep into the cylinders either because of using long push rods instead of the shorties and or too thick of linings requiring the shoes pushed hard and deep into the wheel cylinders.

This letting fluid get by the piston lip cup.

Just some ideas.....

  • Like 1
Link to comment
Share on other sites

I fought the same thing on FEF (think I did the tear apart and reassembled 4 or 5 times).  Got a swap from VPW and fixed the problem straight up, something is out of tolerance.

Link to comment
Share on other sites

10 hours ago, Dodgeb4ya said:

 

One other thing I've had happen is the pistons and cups being pushed too deep into the cylinders either because of using long push rods instead of the shorties and or too thick of linings requiring the shoes pushed hard and deep into the wheel cylinders.

This letting fluid get by the piston lip cup.

Just some ideas.....

 

I had your problem when I redid the brakes on a '38 Chrysler I had. The problem was the one mentioned above. These shoes did not use push rods (pins) against the piston but the shoe itself fit a slot on the piston. A bit different than later Mopars. I ended up cutting about 1/8" of the end of each shoe and this solved the problem for me. You may well have the wrong pins for the brand of brake cylinders you have. Common problem and not necessarily related to the cylinders being Chinese. I have seen this with North American made cylinders as well.

 

Personally, I like to send my brake cylinders out to be re-sleeved to original specs. That way you know the pins are the right ones and most places who re-sleeve give you a lifetime guarantee.

Link to comment
Share on other sites

Just a little note on my experience. 

 

When I was only attempting to make my old 38 Plymouth road worthy somewhat, so I could see what I was really getting into....I was trying to control some of my expenses. The brakes were old and the wheel cylinders rusty and leaking. I sourced new piston rubber and the outer rubber boots. I cleaned up the cylinder bores with emery cloth. I cleaned everything up and reassembled. 3 of the 4 cylinders sealed up great! One was weeping about 2 weeks later. I took it off again. I spent some more time with the emery cloth with my thumb in there, working on the rough spots. That was 7 months ago. 1500 miles later all are still dry and working well. The two rear cylinders were the stepped type you also mentioned. I figure my old cleaned up cylinders are probably better than today's new Chinese cylinders.

 

Edited by keithb7
Link to comment
Share on other sites

7 hours ago, RobertKB said:

 

I had your problem when I redid the brakes on a '38 Chrysler I had. The problem was the one mentioned above. These shoes did not use push rods (pins) against the piston but the shoe itself fit a slot on the piston. A bit different than later Mopars. I ended up cutting about 1/8" of the end of each shoe and this solved the problem for me. You may well have the wrong pins for the brand of brake cylinders you have. Common problem and not necessarily related to the cylinders being Chinese. I have seen this with North American made cylinders as well.

 

Personally, I like to send my brake cylinders out to be re-sleeved to original specs. That way you know the pins are the right ones and most places who re-sleeve give you a lifetime guarantee.

Thst's true it might not be Chinese related but I love to blame the garbage auto parts shipped from there.? Made my ending years of work extremely frustrating.

Yep the older cars and trucks mostly did not use the push rods just the toe of the shoe.

New wheel cylinders always came with new pins and assembly lube...not anymore...just hope and pray quality.

Re-sleeving is the right/safe way now days.

  • Like 3
Link to comment
Share on other sites

I was able to get back to working on my brakes today.  Because of all of your great input, problem is solved.  The pistons were too deep in the cylinders. 

 

My brakes have no push rods on the cylinders.  The shoes fit directly to the pistons.  All I had to do was adjust the cams so the toes of the shoes made more contact with the drums.  It didn't take much to make a difference.  The bleeding then went well. 
 

I had followed the adjusting procedure in my manual.  But, there was a note in the manual that explained why it was better to have more clearance between the shoe toe and the drum rather than too little, so that is what I initially did.  I didn't realize how much that was affecting the pistons.

 

Robert, that was also a great idea to trim the end of the shoes.  I did not trim them (yet) but now I can see how a 1/16 to an 1/8 would allow for a better shoe adjustment.  

 

Thanks again for your help!

 

  • Like 2
  • Thanks 1
Link to comment
Share on other sites

I too noticed that many posts have no conclusion.  To me it is just a courtesy to those who spent their time to share their experience or perspective.  I appreciate the many intelligent and skilled members on this forum!

  • Like 6
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.

Terms of Use