So here is MY brake story....scratching my head.

[Bmartin]

Dave72dt-If you look at the picture(blurry) I included on post #74, you can see the washer.  Its the last thing to go on before the spring clip and sits between the back of the piston and the clip.  I assume its there to give a wide area for the clip to push against.  Its also in the same spot on my old master cylinder. 

 

Rich - I do not think I got any directions with the kit.  I inteded to use the diagrams in the manual and those included on this thread.  If you have the directions to post or send, that would be helpful.  I am suspect of the relief valve as well, it had some lint that I cleaned off it, but I couldn't see anything inside.  Thanks again for your patience with the adjustment tool. 

 

ledfootslim-At this point, I have a firm pedal.  So the issue is the brakes not releasing.  If I'm able to solve the brake release issue, I hope my pedal remains firm or its back to square one. 

 

When I have the master cylinders out, what is the best way to determine that I am getting the proper travel of the piston(piston length correct, spring length correct)?  When static, if I stick the wire through the relief port and it goes through it should only hit spring correct?.  If I see rubber through the relief port then the piston is too far forward.  When compressed completely, I assume the secondary cup should not go past the inlet port or fluid would leak out the back.  Anything else to look for?

 

I truly appreciate all the help from all the forum members.  Hopefully this will help someone else one day. 

[Dave72dt]

My concern was the washer may have been replaced at some time with one that was too thick, thus pushing the piston ahead too far. You should see the rubber cup start to cover the relief port as soon as you start to push the piston forward.

[desoto1939]

Brian. resend me your home email and I will then send you the instruction sheet on the master cyl rebuild.

 

Rich Hartung

desoto1939@aol.com

[Don Coatney]

Brian. resend me your home email and I will then send you the instruction sheet on the master cyl rebuild.

 

Rich Hartung

desoto1939@aol.com

Rich, Might be helpful if you could post that instruction sheet in the Resources/Tech/Brakes section of this webpage linked below.

 

http://p15-d24.com/page/p15d24/tech/brakes.html

[Bmartin]

OK, I took the two master cylinders apart and I have the rebuild kit.  I layed them out next to each other and there are some noticeable differences.  I also pulled out my repair manual and scanned in the master cylinder adjustment instructions and the master diagrams.  Here is a picture of the disassembled parts next to each other, the new master is on the left, the old master is in the center, and the rebuild kit is on the right.  I took some measurements and the bore's are the same at 3.75", the pistons and the main cups (all 3) are the same as well. 

 

 

The first difference I noticed was that the two washers are different, the one from the old master has a lip while the new one is flat.  This would essentially make the piston sit back further in the bore.  Actually it would make the piston sit further forward in the bore since the stepped down area protrudes further into the bore.

 

 

Next you see the springs are different free lengths.  The new master is 4" and the old is 3".  Interestingly, the old master was not noticeably easier to disassemble and the springs felt approx. the same stiffness. 

 

 

 

Finally, the two masters had the rubber gasket/washer in different places.  The old master had it between the piston and the main cup.  The new one had it at the very end near the output.  Now it was there because I put it there.  The gasket/washer fell out of the master when I was disassembling it and I THOUGHT, that was where it should go.  So I could have been wrong.  This would limit the final travel of the piston a bit at full compression and may have opened up the relief port the back side of the piston sooner than intended. 

 

 

Lets talk about that rubber gasket/washer.  In the diagram in the factory repair manual, there is nothing that looks like that piece, but it exists in all three instances.  The only thing that comes close is the part labeled  "11-Piston Washer".  Now the pick makes it look like a thin metal washer, but that could be deceiving.  It also shows it between the main cup and the piston, where it was in the old master.  So that could be an issue. 

 

 

Lastly, lets read the factory repair manual.  Under minor adjustments it states "do not change the piston rod adjustment unless it is definitely known that the piston rubber cup does not uncover the relief port when the pedal is in the full released position. "

 

 

This is what I was trying to determine on both of the master cylinders before disassembly.  I could not see anything so I poked the .03" welding wire into each hole when it was fully released.  The new one went through and was free.  The old master went through, but would hit something metal a little ways in, I chalked that up to the spring.  When I moved each master in a little, I felt rubber in both of them. 

 

 

 

This leaves me with a number of options:

 

1. The old master is showing some minor scaring on the bore.  I can try and take that out with my brake hone, rebuild it just as diassembled, but with the new parts and try that.

 

2.  I can reassemble the new master, but with the piston washer on the piston instead of the end of the bore. 

 

3.  I could swap the shorter spring to the new master and try both piston washer positions

 

4. I could leave all else the same but swap in the new valve on the new master since that was what we guessed might have issues. 

 

And on and on. 

 

At this point, I'll wait for Rich's assembly directions and try to match those.  Then decide what permutations to try. 

Edited March 20, 2014 by Bmartin

[DJ194950]

Very detailed report back, expect it can others with their brake / master cyl. problem diagnosis when finally resolved, and Most likely get you an answer!

 

Good work!

 

Doug

[Dave72dt]

Which one was locking up, the one with the rust or the one with the black paint?  The rusty one appears to have the pieces laid out in correct order.

[Bmartin]

The one on the left is the new one and the one that was locking up.

[Bmartin]

I was doing some thinking.  I started to get my pedal back after readjusting and then using the vaccum bleeder.  I'm concerned that the vaccum bleeder is the reason for the master cylinder not releasing pressure.  The valve in the master is just a little piece of rubber and may have gotten stuck.  Has anyone ever had an issue using a vaccum bleeder?

 

Question:  What is the purpose of the valve in the master?  The piston will push fluid out and the return springs will push the fluid back to the master.  Does the valve limit the flow to prevent cavatating or areation?  Not sure. 

[Don Coatney]

Many years ago someone on this forum had a problem using a vacuum bleeder. I don't recall the issue but you can build a pressure bleeder for the cost of a small garden sprayer.

 

[TodFitch]

I never had good luck with a vacuum bleeder. Seemed like air was leaking into the cylinders via the threads of the bleeder screw. I've had much more luck with the traditional two person, step on the pedal bleeding.

 

But the pressure bleeder made from a garden sprayer for less that $25 really has been the best way for me. That cost included the fittings I needed to make an adaptor for my master cylinder. Since I have DOT5 in my Plymouth I did not want to use the sprayer's built in pump as it would entrain air into the fluid so the cost also included a Schrader fitting for the top side to put pressure into the container.

[P15-D24]

I never had good luck with a vacuum bleeder. Seemed like air was leaking into the cylinders via the threads of the bleeder screw. I've had much more luck with the traditional two person, step on the pedal bleeding.

 

But the pressure bleeder made from a garden sprayer for less that $25 really has been the best way for me. That cost included the fittings I needed to make an adaptor for my master cylinder. Since I have DOT5 in my Plymouth I did not want to use the sprayer's built in pump as it would entrain air into the fluid so the cost also included a Schrader fitting for the top side to put pressure into the container.

Totally agree with Tod, vacuum pump bleeding is more trouble than it's worth. Buy/make a pressure bleeder and you can complete the whole job in less than 10 minutes. 

[Bmartin]

Yah, I'm going to skip the vaccum bleeder.

 

I took the rebuild parts and put them in the new master tonight.  First I tried the rubber gasket/washer behind the piston cup, like my old master was assembled.  As I thought, it blocked the relief port.  So I reassembled with the gasket/washer at the outlet end of the master.  Installed and bled the system using the pedal method.  Same result, all four brakes locked.  I bled the pressure and the master, then went around to each wheel to bleed any pressure there.  I adjusted the minor adjusters out a little and them pumped up the brakes again.  This time the rears didn't lock up, the fronts got tougher to spin, but did not lock.  Could be just air in the system keeping them from locking or perhaps my tight adjustment was too tight.

 

Any reason an overly tight adjustment would keep the master from releasing?

 

I was going to rebuild the old master, but its got a lengthwise scratch in the bore.  I can still feel it with my finger nail after working it with a brake hone.  Not sure if I can take out enough with the hone to make it usable. 

 

That's all the time I have for this week.  Might get a few hours next week, but I'm booked for a while. 

Edited April 1, 2014 by Bmartin

[Dodgeb4ya]

Vacuum bleeding any modern or antique brakes with a professional bleeder tool like a Vacula brake bleeder- $300.00  ,  it's fast and easy but require's a compressor and using it right.

 

Hand held trigger type bleeders work but are slow and sometimes don't pull enough vacuum to do the job properly. Pressure types work well and will get the job done-bubbles stop coming out the hose you're done.

 

So...as per the book-  When beginning to vacuum bleed a wheel cylinder with either a hand held or canister type bleeder connect the vacuum suction hose to the closed off bleeder screw. Build up vacuum in the tool, then open the bleeder screw to vacuum bleed the cylinder and line. 

 

When you're finished vacuum bleeding a cylinder you close off the bleeder screw with the bleeder tool still reading high vacuum and still sucking fluid.

 

Open the beeder screw only a half turn-prevents excessive suction of air around the bleeder thraeds. It's normal to see bubbles in the suction hose even after more than 2-3 minutes of vacuum bleeding because of a small amount of air being sucked around the bleeder threads. This is normal.

 

Vacuum bleeding fails to do the job properly when you disconnect the vacuum bleeder hose from the bleeder screw without closing the bleeder screw first. A very small amount of old fluid and air sucked out will be pulled back into the wheel cylinder or brake caliper.

 

I myself use both  pressure and vacuum type bleeders for brake jobs. A pro shop canister type vacuum bleeder works very fast and can be used on DOT 3,4, and 5 systems with out worry of contamination. Just costs a lot of $$$. I prefer it.

Bob

[Bmartin]

I'm looking at changing out all of my brake lines.  I called up inlinetube and they have a kit for a 1941 Plymouth with 117" wheelbase.  I need to go home and check my wheelbase, but anyone know if the 1941 would be the same as the 1940 I have?  Prebent would be a real time saver.Thanks.

 

EDIT:  I confirmed the wheelbases were the same so I went ahead and ordered it.  We'll see how easy it fits. 

Edited March 27, 2014 by Bmartin

[desoto1939]

Brian:  question for you. Since the brakes are locking and when you get this locking is the brake lights lite up on the car.  I would assume this would be happening since this then would be fluid pushing up on the brake light switch.  Could there be some blockage in the  brass connector that has the brake light switch and all four lines that run to the brakes and MC.  So two lines to the front. One line the rear and one line from the MC.  Night want to check this might be the culprit.  Just thought.

 

Rich Hartung

[Bmartin]

 

Just a quick update.  The brakes are no longer locking.  I backed off the adjustment a tadd and retorqued the main adjuster bolts with a torque wrench.  I'm back to not having a pedal again.  Locking could have been over torqued main adjusters, too tight an adjustment, or an effect of the vaccum bleeder. 

 

New hard lines on order since I may have seen some wet threads around a rear line.  planning on making the pressure bleeder and then isloating the system to just the fronts again.  Then work from there.  Berbaum did not have any distribution blocks, but I did order a new brake light switch and rebuild kits for the rear wheel cylinders.  This gives me some options. 

[_shel_ny]

For anyone wanting to make a pressure bleeder.

 

Ace Hardware 90th Anniversary sale starting tomorrow (April 2) has a 1 gallon sprayer for $3.99 that would likely do the deed.

 

 

EDIT:  I believe if you are using Dot 3, or Dot 4 fluid (may be OK with Dot 5 silicone) you must clean this well after use to be able to use it again down the road. I believe denatured alcohol works for that purpose. At $4, basically disposable.

Edited April 2, 2014 by shel_ny

[Bmartin]

I picked up the 1/2 gallon sprayer.  They no longer use a hose barb on the tank.  So I'm going to head back and try to find the correct fitting to convert the threaded part on the sprayer to 1/4" hose barb.  Alternately, I may be able to use a fitting with 1/4" hose barb on both sides to connect the sprayer hose with the clear hose extension. 

[james curl]

I have a vacuum bleeder that uses compressed to draw a suction on a pint plastic bottle.  I fill the bottle with brake fluid then connect it to the empty sprayer on one side and the top of the master cylinder on the other side.  Once you pump up the sprayer you pressurize the bottle of fluid.  This keeps the brake fluid out of the sprayer hoses and handle, allowing long use of the sprayer. 

[TodFitch]

I picked up the 1/2 gallon sprayer.  They no longer use a hose barb on the tank.  So I'm going to head back and try to find the correct fitting to convert the threaded part on the sprayer to 1/4" hose barb.  Alternately, I may be able to use a fitting with 1/4" hose barb on both sides to connect the sprayer hose with the clear hose extension. 

 

I simply cut off the spray tip from the wand and put my new hose on there with a clamp to secure. That left the original valve mechanism intact which I find useful.

 

Instead of putting a pressure gauge on the side of the tank I put a Schrader valve. I fill it from there which is above the level of the fluid so I don't get bubbles in the brake fluid which I would if I used the original built in pump. Since I am using DOT5 brake fluid that is important. I know the pressure in the tank because my tire filling air chuck has a gauge on it.

[DJ194950]

Tod, question-how much pressure do you start with?

 

Doug

[TodFitch]

Tod, question-how much pressure do you start with?

 

Doug

I put 10 to 15 psi into it. Less than 10 psi and I did not seem to get enough flow to really purge the air. More than 15 psi and I was afraid I'd be over pressurizing the plastic sprayer container.

 

Not worried about over pressurizing the brake system itself as I think the max pressure while in service is several hundred psi up to maybe the low thousands. (200 lb man putting maybe un to 400 lbs force on pedal in an emergency. Pedal leverage about 10 to 1 gets to about 4000 lbs. Area of master cylinder piston pretty close to 1 sq. in., so maybe 4000 psi in a panic stop.)

 

Also, originally the cover bolts on the master cylinder started leaking at about 5 psi. Turns out that at least for my year car the washers for the cover are supposed to be soft copper and I had regular lock washers. Couldn't find washers the size I needed so I took some sheet copper stock from the local hardware store and a punch set from Harbor Freight and made some washers that did a pretty good job of sealing the bolts at up to about 15 psi. Again I did not want to take it farther than that on pressure.

[DJ194950]

Tks. for the reply Tod.

 

Been watching the built your own pressure brake bleader forum members have posted for a while and it seems like a cheap and easy thing to do!

 

Doug

[Bmartin]

So I got the pressure bleeder working with a little leakage at the master, but it holds pressure.  I capped off the rears and bled just the fronts.  I have pedal.  It also looked like I have seepage from the passenger rear brake line fitting.  Could a very slow leak, cause you to lose the majority of the pressure in the lines?

 

How long can you leave the fluid in the bleeder until it starts to corrode the plastic?  I want to use it through the weekend and would prefer not to clean it out till then.