Moparts

Question on bench bleeding master cylinder

Posted By: David_Trimble

Question on bench bleeding master cylinder - 09/07/14 11:01 PM

This is a continuing saga of doing a disk brake swap on my '69 Charger using the front spindles from a '77 Diplomat (the car had originally had factory front disks but one of the previous owners had swapped out the front disks to front drums- the MC, booster and prop valve were left on). My garage, being the oven that it is during the summer is finally cooling down to the point where I can work on this conversion w/o having heat stroke.....

This all started as the car never really had very good brakes to begin with. In inspecting the master cylinder in preparation to bench bleeding it (as suggested by a board member when I had initially posted my issue) I found that apparently the front right wheel cylinder had failed and all the fluid had seeped out, leaving me with a empty rear reservoir. Hence the conversion.

Fast forward to now, where everything has been converted and I'm back at square 1 again- bench bleeding the MC. Had the brake lines disconnected and ran hoses back to the reservoirs and commenced bleeding.

I noticed one disturbing thing during the process - while the hoses themselves did not seem to be returning bubbles to the reservoirs, I noticed that the port on the back reservoir was bubbling whenever the pedal was depressed. Also, I could hear a sucking sound as the pedal was released.

The MC had been rebuilt- about 10 years ago. I'm beginning to wonder if one of the seals had failed (and which may've been the cause of all my woes to begin with ), or is this 'normal' operation? (I have a feeling it isn't...)

Thanks once again!
David
Posted By: mikemee1331

Re: Question on bench bleeding master cylinder - 09/07/14 11:29 PM

Quote:

I noticed one disturbing thing during the process - while the hoses themselves did not seem to be returning bubbles to the reservoirs, I noticed that the port on the back reservoir was bubbling whenever the pedal was depressed. Also, I could hear a sucking sound as the pedal was released.


it sounds like an internal leak to me. I feel ya about the garage heat! I bare peek in mine from the end of June to about now!
Posted By: TooMany62s

Re: Question on bench bleeding master cylinder - 09/07/14 11:47 PM

It sounds to me as though you are trying to use the drum brake master cylinder with the disc brake setup. If that's the case I think you need a disc brake master cylinder.
Posted By: David_Trimble

Re: Question on bench bleeding master cylinder - 09/08/14 12:40 AM

Quote:

It sounds to me as though you are trying to use the drum brake master cylinder with the disc brake setup. If that's the case I think you need a disc brake master cylinder.


I'm pretty sure this is a disk master cylinder (I can post a pic of the setup if necessary) - back some years ago when I first found out that my drums were probably not the original setup I had posted a pic of my MC/booster set up, I was told by board members that my current combo setup is actually for disk brakes. So I'm pretty sure I've got a correct disk MC.
Posted By: RapidRobert

Re: Question on bench bleeding master cylinder - 09/08/14 03:31 AM

You meen the blue plastic male fittings that screw into the MC with the 2 short black hoses (the bleeder kit) that it's bubbling on/around the threads on one of the blue fittings? If so tighten it more, if that ain't it holler
Posted By: John_Kunkel

Re: Question on bench bleeding master cylinder - 09/08/14 08:23 PM

Quote:

I noticed one disturbing thing during the process - while the hoses themselves did not seem to be returning bubbles to the reservoirs, I noticed that the port on the back reservoir was bubbling whenever the pedal was depressed. Also, I could hear a sucking sound as the pedal was released.



When you say "bubbling" do you mean air escaping the port or fluid burbling up from the port? Fluid escaping the port on initial pedal movement is normal and is a good sign that the pushrod is adjusted properly.

The sucking sound is probably the booster diaphragm displacing air.
Posted By: Pynzo

Re: Question on bench bleeding master cylinder - 09/08/14 08:56 PM

Quote:

You meen the blue plastic male fittings that screw into the MC with the 2 short black hoses (the bleeder kit) that it's bubbling on/around the threads on one of the blue fittings? If so tighten it more, if that ain't it holler



I made up a set of steel bleeder lines using an old set of m/c to distribution block lines I had sitting around. They seal up better than the plastic kit and no hoses to jump out of reservoir. Bent them so they almost touch bottom of the bowls.
Posted By: floridian

Re: Question on bench bleeding master cylinder - 09/08/14 09:25 PM

Quote:

Quote:





I made up a set of steel bleeder lines using an old set of m/c to distribution block lines I had sitting around. They seal up better than the plastic kit and no hoses to jump out of reservoir. Bent them so they almost touch bottom of the bowls.



Sounds like a great idea.. Nothing worse than almost being done and having a rubber hose pop out....
Posted By: David_Trimble

Re: Question on bench bleeding master cylinder - 09/09/14 04:08 AM

I'll see if I can't answer everyone's posts here...

@RapidRobert: Right, I'm using that Dorman(sp?) brake bleeder kit. Plastic hoses with a assortment of plastic fittings. And yes now that you mention it, those fittings don't fit too well, so they may very well be sucking air somehow- although I'm not finding any seepage from around the plastic fittings. But I'll check on the rear plastic fitting and try to get a better seal on it...

@John_Kunkel: It's definitely air escaping from the port. Specifically, the port furthest back on the MC. Actually there are 2 ports back there, one in front of the other, and I've seen air bubbles coming from both. The port in the front reservoir isn't bubbling, though. And you might be right about the booster making the sucking sound- I'll see if I can't pin down more precisely where the sound is coming from to be sure.

@Pynzo- I'll give that a try (especially if I can't get the plastic fittings to seal) if I can find my set of old lines (I replaced the brake line some years ago- I THINK I have the old lines somewhere)

Might not get to doing this 'till the weekend, but I'll give it a shot and report back in. Thanks for the tips!

David
Posted By: RapidRobert

Re: Question on bench bleeding master cylinder - 09/09/14 04:27 AM

If your talking about bubbles coming from either of the holes in the bottom of the reservoir then that is excellent as air will bleed out there and also from the 2 lines that you loop back over the rim. Keep bleeding! Medium slow strokes and put a block of wood under the pedal to limit the travel to it's normal range
Posted By: David_Trimble

Re: Question on bench bleeding master cylinder - 09/11/14 12:53 AM

Quote:

If your talking about bubbles coming from either of the holes in the bottom of the reservoir then that is excellent as air will bleed out there and also from the 2 lines that you loop back over the rim. Keep bleeding! Medium slow strokes and put a block of wood under the pedal to limit the travel to it's normal range


Ah ok- I'll keep on bleedin' then It's just that I had been working the pedal a good 5 minutes and the bubbles were pretty steady (didn't look like they were slowly going away) But that might be as you say from the possibly bad plastic fitting I'm using, so I'll work on getting that fixed first. IF the bubbles still won't go away then I'll start getting worried again.

Thanks!
Posted By: RapidRobert

Re: Question on bench bleeding master cylinder - 09/11/14 01:27 AM

If they're still a coming after 5 minutes then air is being drawn in thru the blue plastic bleeder fitting threads
Posted By: Pynzo

Re: Question on bench bleeding master cylinder - 09/11/14 03:11 AM

The blue fitting is probably a generic 9/16-18 and the mopar fitting is an oddball 9/16-20. Best you can do is cross thread the plastic. I can lend you these if you want. Pm if interested, but I need them back.

Attached picture 8266956-image.jpg
Posted By: David_Trimble

Re: Question on bench bleeding master cylinder - 10/05/14 09:49 PM

Quote:

The blue fitting is probably a generic 9/16-18 and the mopar fitting is an oddball 9/16-20. Best you can do is cross thread the plastic. I can lend you these if you want. Pm if interested, but I need them back.



@Pynzo- I didn't know about the oddball thread- that explains a lot. And thanks for the offer but that's ok- I can probably cobble together my own with what I can find at the local parts store. I just need the tool that's used to expand the line opening- I've got line cutters so I can probably make it out of stock lines.

Sorry that it's been a while since my last post- life got in the way However I did manage to take another look at the MC today and I found something interesting....

When I left off working on the bench bleeding, I had left the MC about 1/3 full of brake fluid, with the lines from the bench bleed kit still set up. Fast-forward about a month 'till now, when I just took a look at the setup not 5 minutes ago and I found that while the fluid level in the front reservoir was where I had left it, the back reservoir was bone dry again (this is the same reservoir that I had reported seeing bubbles coming from the back port). Also, this is the very same thing I had noticed many months ago which had led me to think the front brake cylinders (one or both) had developed a leak, and had decided to do the front-disk swap rather than fix the cylinders....

However, now I have the lines disconnected and it managed to leak anyway. The first thing I though of was that it had seeped into the brake booster, but inspecting the outside of the booster I didn't find any signs on the booster body of fluid having seeped out of it. Now it's possible that the cheap plastic 'line nut' from the MC bleeding kit may've seeped, and in feeling around it I did find a film of fluid- but only a film. I didn't find any fluid (or a stain where fluid had pooled and then evaporated) under the car, either.

The only thing I can think of is that it did leak thru the back into the booster, but the booster had somehow retained the fluid. I'm going to pull the MC from the booster and take a look and report back on what I find in a bit...

David

P.S. Just pulled it- couldn't find any signs of leakage into the booster. The only thing I can think of now is that I've got a defective MC... :P

P.P.S. Took another look- thought this time to also look at the BACK of the MC- and I found a pretty heavy film of fluid around the bottom of the cylinder itself. So it DOES have a leak.

Posted By: Pynzo

Re: Question on bench bleeding master cylinder - 10/05/14 10:30 PM

Raybestos has a rebuild kit. Check Rockauto for it.
Posted By: David_Trimble

Re: Question on bench bleeding master cylinder - 10/05/14 10:36 PM

Thanks, Pynzo- I'll do that! I was dreading having to go to my local parts store for a rebuild kit....

David
Posted By: therocks

Re: Question on bench bleeding master cylinder - 10/06/14 01:42 PM

NAPA did have the steel fittings on short lines.I bought some years ago.Might need a parts guy that can actually read a catalog though.Rocky
Posted By: RapidRobert

Re: Question on bench bleeding master cylinder - 10/07/14 02:13 AM

Quote:

I can lend you these if you want.

Pynzo is a straight up guy & definitely a credit to our hobby. He offered me a freebe part awhile back . David is this the brake issue from Hell from way back
Posted By: David_Trimble

Re: Question on bench bleeding master cylinder - 10/08/14 12:56 AM

Quote:

Quote:

I can lend you these if you want.

Pynzo is a straight up guy & definitely a credit to our hobby. He offered me a freebe part awhile back . David is this the brake issue from Hell from way back



I'm afraid it is The first time I had noticed the back reservoir being empty I had thought one or both of the front wheel cylinders had sprung a leak- that's why I went into doing the front disk conversion as I was going to do that soon anyway. While I DID find that the front right cylinder had sprung a leak (there was brake fluid all over the inside of the backing plate) apparently the issue was twofold - there was both that issue and a leaky master cylinder.

David
Posted By: David_Trimble

Re: Question on bench bleeding master cylinder - 11/16/14 12:02 AM

An update- found a local shop that rebuilds brake and clutches, and had them rebuild my MC. Long story short though they couldn't rebuild it because:
A) they couldn't find a rebuild kit for it, but it didn't matter as:
B) when they opened it up they found the bore had rusted. So even with a rebuild kit it probably would've required so much honing to clean out the pitting that the kit would've been useless.

So they wound up locating a rebuilt MC as a replacement, which ran me about as much as the rebuild was going to.

So right now the MC is back on the car, I've hooked up the bleeding kit (keeping in mind the aforementioned problem with the brake line threads rear cylinder don't quite work with what the bleeding kit has), and while the front seems to be bled ok, I still hear/see air in the back reservoir.

My next step now is to go to NAPA and see if I can't cobble together a better MC bleeder setup with correct threads as I'm positive the air's getting pulled in from the badly-fitting plastic nut I'm using in the bleeder kit...

David
Posted By: RUNCHARGER

Re: Question on bench bleeding master cylinder - 11/16/14 12:15 AM

If you have a JY of parts car near, pull the lines off it, trim the lower ends off and use them to bench bleed it.

Sheldon
Posted By: savoy64

Re: Question on bench bleeding master cylinder - 11/16/14 02:32 AM

teflon tape it...
Posted By: 340duster340

Re: Question on bench bleeding master cylinder - 11/16/14 04:28 AM

hold your thumb over the hold for the piston out stroke to prevent air from going back in. its ghetto, but it will work in a pinch. repeat as needed, you will need to watch the fluid shooting out to see if there is air in it.
Posted By: RapidRobert

Re: Question on bench bleeding master cylinder - 11/16/14 05:00 AM

Quote:

hold your thumb over the hold for the piston out stroke to prevent air from going back in. its ghetto, but it will work in a pinch. repeat as needed, you will need to watch the fluid shooting out to see if there is air in it.

Have a helper wrap/hold a big towell around/underneath the MC/lines to catch the mess. You work the pedal. EDIT put a brick or block of wood under the pedal so it dont travel past its normal range
Posted By: David_Trimble

Re: Question on bench bleeding master cylinder - 11/17/14 12:25 AM

Re: using JY lines..... what newer model Mopars would I look for that would have compatible lines?

Failing that, that's a good idea using teflon on the back bleed line retainer. I'll also give that a shot, and use the thumb as a check valve.. I'm also watching the back reservoir level to make sure this replacement doesn't have the same issue as the old one - or I'll be back to square 1 again...

Oh and good point about the brick- I had almost forgotten about that.

David
Posted By: 340duster340

Re: Question on bench bleeding master cylinder - 11/17/14 05:15 AM

you can buy the flare nuts new and bend up your own lines.

also thexton makes a master kit for bench bleeding master cylinders. includes all flare nut sizes metric and standard. here is one i found off amazon, there is another kit that has the carry case and some other stuff.

http://www.amazon.com/Thexton-804-Master...ton+bleeder+kit


either way its a straight forward process once you have the right equipement.
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