rebuilding brakes

[broker-len]

I have both a 32 PA and 36 Pymouth      several years ago I had the wheel and master cylinders resleaved  by APPLE hydraulics in NY   they used brass    I have had great susses with the 32    brakes stay up and do not pull    the pistons on the 36 which are steeped seems to develop some kind of white substance which locks them up    I lightly hone the holes and sand and use a bench wire wheel  on pistons----    I do not put many miles on either car---am in the process of rebuild them for the second time----       I do have four wagner replacements which I will use if I have to go through this again   can any one give me a clue why I have having this issue------------thanks in advance

[hwellens]

Use stainless steel pistons. I put them in my 38 Dodge years ago; still no problems. Not sure where to buy them now.  The white substance is probably the aluminum pistons corroding.

[36humpback]

4 hours ago, broker-len said:

I have both a 32 PA and 36 Pymouth      several years ago I had the wheel and master cylinders resleaved  by APPLE hydraulics in NY   they used brass    I have had great susses with the 32    brakes stay up and do not pull    the pistons on the 36 which are steeped seems to develop some kind of white substance which locks them up    I lightly hone the holes and sand and use a bench wire wheel  on pistons----    I do not put many miles on either car---am in the process of rebuild them for the second time----       I do have four wagner replacements which I will use if I have to go through this again   can any one give me a clue why I have having this issue------------thanks in advance

If your 36 takes them, I have a sleeve of 1 1/8 pistons somewhere in my collection.  Bob

[Frank DuVal]

6 hours ago, broker-len said:

seems to develop some kind of white substance which locks them up  

I see this all the time with DOT 3 systems. Caused by moisture in the air. Master cylinder reservoirs on these older cars are open to the atmosphere. Modern cars use a rubber diaphragm between the atmosphere and the fluid reservoir. Now, why one Plymouth does it and not the other....good question.

 

I fix it by using DOT 5.

[Graham Man]

2X on the aluminum corrosion it is horrible with brake fluid.

 

 

I just started using silicone brake fluid DOT5, working great so far working on my second car conversion.  But my big breakthrough was using silicone disk brake grease.  I slather everything when I am assembling the wheel cylinders, including the aluminum pistons, and anything else that could corrode (I fill the piston fins with grease).  Almost ten years out and no problems with my brakes, my cars sit months at a time, wish I had more time to drive them.

 

 

I slather all internal surfaces, springs, cups, pistons, and put a little extra between the outside dust boot and the aluminum piston.  I also use it for all my points of movement, with the shoes.  It is extremely sticky and good up to 500F.

 

[broker-len]

you mention a PISTON FIN   not sure what that is   I have some NAPA  anti seize   lube     I painted the piston with the stuff and reassembled   what I am getting from the post is that aluminum can deteriorate   the ones in my car are some what pitted      so we will see in a few years     thanks for your advise

[Frank DuVal]

6 hours ago, broker-len said:

I have some NAPA  anti seize   lube 

What type?  It needs to be compatible with brake fluid and rubber parts.

 

I've been using DOT 5 since the early 80s. Never any white corrosion on parts when I opened them back up, but, I haven't had to open many of them!😉

[37_Roadmaster_C]

I think @Frank DuValhas a very good suggestion.  Old brake master cylinders reservoirs are open to the atmosphere. The Dot 3 brake fluids commonly used in those systems attract water out of the air like a sponge! When you get water in Dot 3 fluid you now have a BIG problem! The water will rust brake lines and cylinders and will definitely cause corrosion to dissimilar metal parts, just like on boats. The way I have solved this issue is like Frank did. I cleaned the systems thoroughly then used Dot 5 silicon fluid. The Dot 5 fluid will not absorb water and works great. One thing about the Dot 5 fluid is that it forms small air bubbles if shaken or poured fast. The bubbles will slowly go away, but the can leave a small amount of air in the system. The secret is to pour slooooowly with a guide to help avoid bubbles. The guide I speak of is any small CLEAN rod held against the bottle opening and in the reservoir while pouring (I use a clean screwdriver). It is not perfect, but it helps a lot. The other thing is to let it sit after filling to allow the bubbles to go away. It takes time, but it is very worth it!!!

Just my $.02 if anybody likes the thoughts n😇.

[broker-len]

I have never used Dot 5----my two old cars are dot 3----what do I need to do to change over----is it just draining the old and putting in the new or do all and cylinders need to come apart and be cleaned and how about the lines     thanks in advance

[Matt Harwood]

You can typically flush the system with denatured alcohol or something similar, then fill with DOT 5. Disassembly should not be necessary unless you're seeing a lot of corrosion that should be addressed.

[Graham Man]

I have used anti seize...the problem is it dries out after about 5 years and then the system seizes up....  Ask me how I know. 

On the bright side the anti seize prevents oxidation so it is easy to clean up.

 

2X on the denatured alcohol

Edited April 21, 2021 by Graham Man (see edit history)

[Ltc4748]

In 1993 I rebuilt my 48 Chrysler brake system. I used silicone dielectric grease to lubricate everything. the sealing cups, pistons, the cylinder walls, and the inside of the outer rubber dust boots on all 6 wheel cylinders and the master cylinder, then assembled them. I filled it with DOT5 fluid and bled the system and adjusted the brakes. It is now 2021 and that brake system still works flawlessly. The car sat since 1995 when my father passed away and I started it again late last year and again two weeks ago. Since then I have done many brake systems for other hobbyists and they all have experienced the same long lasting results. I agree with Graham man, the break through is the grease. 

[ipeeforward]

In 2001 I overhauled the whole brake systems on a Bedford CA (van) that uses a Lockheed system. Everything was removed and cleaned with denatured alcohol (methylated spirits this side of the pond) including the brake pipes on the vehicle. All the rubber components were replaced with new old stock items as that was all I could get at the time.

I decided to switch to silicone brake fluid at this point. Within a few days of completing the work I had problems with the brakes sticking on and excessive pedal travel (shoes were adjusted correctly and there was clearance on the brake pedal).

On disassembly I found the master cylinder seals had swelled a considerable amount blocking the compensating port and the wheel cylinder seals likewise had also increased in size.

I could only assume that the rubber they were made of way back when wasn’t compatible with the silicone fluid? I gave up on the silicone fluid and returned to dot4 with another set of seals. Other than changing the fluid regularly I have had no problems since.

I have used rubber grease in the wheel cylinders around the aluminium pistons to try and stop the corrosion that seems to occur. I may switch to the silicon grease next time any work is required. 
In my normal day job as a mechanic I often will pull apart a new wheel cylinder and add silicon grease to the bore as they sometime very dry where they have sat around after manufacture.

I have a number of customers with classics running silicon fluid with no problems. Like other posts you have to be careful when filling up to avoid bubbles. The fluid also seems very expensive in the UK.