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Line locks and master cylinder failure


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I dropped my car off at the mechanic to install the line lock as I generally prefer to leave brake works to someone else.

 

They had a problem bleeding the brakes and pulled the master cylinder and found it leaking into the booster.

 

The master cylinder was replaced less than 5,000 miles ago.

 

The prior master cylinder had failed after the conversion of the rear brakes to disc

 

I replaced it with http://www.streetortrack.com/Master-Cylinder-for-4-wheel-disc-1964-73-Mustangs-pr-23771.html this master cylinder.

 

Two questions

 

Could improper installation or bleeding have caused this failure?

 

And with the brake booster full of brake fluid, is it likely that it will have been damaged?

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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Bleeding no , and the brake fluid should not effect the diaprahm in the booster.

 

There is a rod between the booster and master that connects to the pedal assembly, if that rod is not adjusted correctly then when you push on the brake pedal all the way down it may damage the push rod in the master.

 

 

Also what type of brake fluid are you using, dot 3,4,5.1 or converted to silicon dot 5?

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we hear stories about the newer dots causing seals to fail, but dot 3 would not cause that unless the break system had a contaminate in it or dirt that would ruin the O ring.

since your brake system is no longer stock i don't know what effect the rear disc is having. in the manual there is a section talking about the correct pushrod length between the master and booster. you would have to pull the master out to get to the pushrod, then there is a way to measure the length. it may not be the problem.

 

its very possible the new master wasn't 100% from the start. may of them are refurbished units and maybe the bore wasn't good inside to start.

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Well the master I had was a scott drake part. I spoke with my mechanic about pushrod length and he said that if it was too short or too long the brake pedal height would be either high or low and he felt that this is not an issue.

 

I think I have found a rebuild kit for the master, though it is a bit hard to tell til I get it in hand.

 

perhaps it was a manufacturing defect, but my prior master failed after the rear brakes were installed

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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I know the MC form SOT says for 4 wheel disc brakes. However, if they did not remove the 10# residual pressure valve from the MC output port for the the rear brakes it may cause some problems. I would think the symptom would be rear brake dragging (no 2# residual valve required for high mounted MC). It may be a stretch but......

The rubber valve and spring are behind the brass seat in the MC output port in case you want to look. Just an idea. Chuck

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I was planning on doing that if the rebuild parts arrive, but they did not today. I am not completely lost when it comes to brakes, I have over the years replaced pads, rotors, shoes, wheel cylinders, drums and even have rebuilt one master cylinder, but I purposely stay away from working on them now and that is part of what is so frustrating.

 

I wish I could find a factory part from another year that would bolt up and work with no major headaches! Looked at a 1995 Mustang GT MC and the bore size is right, but the ports are on the opposite side and not sure if the pushrod length would be something close

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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I don't know Jeff you seem pretty talented at fabrication. Go to a pick and pull and grab the MC, booster, and peda off a 95. Who knows what you may come up with? :cool:

2rr7aiv.png

 

Just cruising along minding our own business when BAM!!! The LAWS show up.

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I don't know Jeff you seem pretty talented at fabrication. Go to a pick and pull and grab the MC, booster, and peda off a 95. Who knows what you may come up with? :cool:

 

Um . . . . hell no! If I could use the MC on my booster and pedal set up and just had to bend some custom lines, maybe, but I like the way my brakes felt and really want to keep it close to where it was.

 

Now a pull a part would get me the pushrod and the lines and fittings. . . hmmm

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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I did a disc conversion in the rear as well, I ditched the old school steel capped MC for one out of a early 90s Crown Victoria. It bolted right up to the stock booster and works great with the discs all around.

"BOSS 331"

73 fastback

331ci stroker

wide-ratio toploader

power discs front & rear

9" trak-lok axle w/ 3.70:1 gears

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I did a disc conversion in the rear as well, I ditched the old school steel capped MC for one out of a early 90s Crown Victoria. It bolted right up to the stock booster and works great with the discs all around.

 

There ya go! ::goodjob::

2rr7aiv.png

 

Just cruising along minding our own business when BAM!!! The LAWS show up.

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  • 2 weeks later...

I went with a Wilwood 1 1/8 bore MC. Everything works now, but the feel is not "right" I suspect the pushrod length is short as the pedal feels like there is air in the lines at the bottom of its travel, but the brakes work well. It will pump up with the second application and vacuum seems irrelevant.

 

Took it to an impromptu car show Friday and got lots of attention.

 

Now that the rain has stopped, it is back to work :( Hopefully I can get to it one evening between maintaining the yard and doing some minor renovations to the house.

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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I went with a Wilwood 1 1/8 bore MC. Everything works now, but the feel is not "right" I suspect the pushrod length is short as the pedal feels like there is air in the lines at the bottom of its travel, but the brakes work well. It will pump up with the second application and vacuum seems irrelevant.

 

Took it to an impromptu car show Friday and got lots of attention.

 

Now that the rain has stopped, it is back to work :( Hopefully I can get to it one evening between maintaining the yard and doing some minor renovations to the house.

 

This will sound stupid but if you have four wheel disc, adjust the ebrake up a little.

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I went with a Wilwood 1 1/8 bore MC. Everything works now, but the feel is not "right" I suspect the pushrod length is short as the pedal feels like there is air in the lines at the bottom of its travel, but the brakes work well. It will pump up with the second application and vacuum seems irrelevant.

 

Took it to an impromptu car show Friday and got lots of attention.

 

Now that the rain has stopped, it is back to work :( Hopefully I can get to it one evening between maintaining the yard and doing some minor renovations to the house.

 

This will sound stupid but if you have four wheel disc, adjust the ebrake up a little.

Doesn't sound silly.

 

Unfortunately I already have my ebrake cables as tight as I can get them without the rear brakes dragging. The Baer Ironsports use a spring loaded lever on the caliper to engage the pads rather than shoes.

 

Are the pushrods in our cars adjustable, or do I go find a longer one and trim it to length?

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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Guest BigPinoyHunk

our cars originally use a 1 inch bore. i went with our stock booster with a 2002 mustang v6 MC. it has the same bore as our stock MC and is prop'd for disc/disc brakes already.

 

i have the 94-04 cobra brakes all around and the thing will straight up STOP. i can go 60-0MPH with ease ( i live with alot of open roads around here and have alot of special roads to do this ).

 

just use the stock PB and a later MC. however it sucks that the outputs of the MC go out of the engine side. i've heard of guys from other forums using MC's from trucks or something else that has the outputs on the fender side which i wish i would of done. because of this, i can't go crazy with valve covers on my motor.

 

i believe the vehicle i'm talking about is a 2004 ford explorer sport trac is what has all disc brakes and has the outputs on the fender side. might even be a 5.0 f150.

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I went with a Wilwood 1 1/8 bore MC. Everything works now, but the feel is not "right" I suspect the pushrod length is short as the pedal feels like there is air in the lines at the bottom of its travel, but the brakes work well. It will pump up with the second application and vacuum seems irrelevant.

 

Took it to an impromptu car show Friday and got lots of attention.

 

Now that the rain has stopped, it is back to work :( Hopefully I can get to it one evening between maintaining the yard and doing some minor renovations to the house.

 

This will sound stupid but if you have four wheel disc, adjust the ebrake up a little.

Doesn't sound silly.

 

Unfortunately I already have my ebrake cables as tight as I can get them without the rear brakes dragging. The Baer Ironsports use a spring loaded lever on the caliper to engage the pads rather than shoes.

 

Are the pushrods in our cars adjustable, or do I go find a longer one and trim it to length?

 

I had to make mine to fit the Wilwood to Ford pedal so mine is adjustable.

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But you aren't using a Vacuum booster are you?

 

I really think it is a short pushrod leading to a less than full compression of the MC piston. I feel NO resistance in the 1st inch of pedal travel (keep in mind the pivot point is going to result in a lot less movement at the booster than at the end of the pedal. I guess I'll have to pull the pushrod, and try something a little longer and tweak to get the feel right.

 

Prior MC was a converted unit by Scott Carpenter and had a 1 1/16 bore so I don't think the 1 1/8 inch is a problem unless I delete the booster in the future (no thanks)

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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But you aren't using a Vacuum booster are you?

 

I really think it is a short pushrod leading to a less than full compression of the MC piston. I feel NO resistance in the 1st inch of pedal travel (keep in mind the pivot point is going to result in a lot less movement at the booster than at the end of the pedal. I guess I'll have to pull the pushrod, and try something a little longer and tweak to get the feel right.

 

Prior MC was a converted unit by Scott Carpenter and had a 1 1/16 bore so I don't think the 1 1/8 inch is a problem unless I delete the booster in the future (no thanks)

 

No mine is four wheel manual all the way and will stop on a dime with little effort

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If this can't get tuned to my satisfaction that is my backup plan

 

and thank you chuck, I'll pull it and see what I can accomplish this weekend

http://www.7173mustangs.com/gallery/1_01_07_15_8_53_18.png

 

"I love my Hookers!" and "Get some Strange" probably have a different connotation to non automotive enthusiasts!

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