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brake repair
#1
I'm replacing the front disc brakes on my 73 mach 1.  I removed the calibers and the rubber brake lines.  It was a few days before I got back to putting new calibers and lines back on.  Went I went to fill master cylinder I discovered that both sides were completely empty.  

My question is should both sides have drained down?  I thought just the side that covered the front brakes would have drained.

thanks
Bob
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#2
I would pull the master cylinder off and pop the snap ring out of the end holding the piston in. There is also an allen head button head screw in the bottom that has to come out to get the piston out. There is an o-ring on the screw. If it is rusty inside then the fluid probably drained out and into your booster and down it and eats the paint off. 
If rusty you can hone it some and install a rebuild kit or send off and get a brass sleeve put in if you want to keep the original. Last one I got at parts house does not look like the original. 
You should change the fluid from time to time to prevent the moisture from getting into the system causing rust in the master cyl., rear wheel cylinders and in the caliper. 
Another place you can get a leak is where the rear metal brake line crosses over from the junction block to the R.H. rear brake. There is a metal tab welded to the axle housing that holds the line in place and the line gets rusty there and can blow out.
One of my checks before driving is to put both feet on the brake pedal and push as hard as I can to blow out any weak spots before I leave the garage.


When a man is in the woods and talks and no women are there is he still wrong??
Tongue
David
[+] 1 user Likes Carolina_Mountain_Mustangs's post
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#3
(11-11-2019, 12:36 PM)Carolina_Mountain_Mustangs Wrote: I would pull the master cylinder off and pop the snap ring out of the end holding the piston in. There is also an allen head button head screw in the bottom that has to come out to get the piston out. There is an o-ring on the screw. If it is rusty inside then the fluid probably drained out and into your booster and down it and eats the paint off. 
If rusty you can hone it some and install a rebuild kit or send off and get a brass sleeve put in if you want to keep the original. Last one I got at parts house does not look like the original. 
You should change the fluid from time to time to prevent the moisture from getting into the system causing rust in the master cyl., rear wheel cylinders and in the caliper. 
Another place you can get a leak is where the rear metal brake line crosses over from the junction block to the R.H. rear brake. There is a metal tab welded to the axle housing that holds the line in place and the line gets rusty there and can blow out.
One of my checks before driving is to put both feet on the brake pedal and push as hard as I can to blow out any weak spots before I leave the garage.
I had pretty good brakes before changing the front disk.  The backs shoes were good and dry.  When I pulled front wheels I saw that the hoses where pretty bad, rubbers where missing on the caliber slide bolts, one caliber wouldn't retract far enough so I replaced both.  
I just thought with front lines removed only one bowl would drain down and that something must be wrong with master cylinder.  I also found that the plug to proportional valve was not connected and one wire was broken.  I'm leaning toward replacing master cylinder and proportional valve.  The last time I did replace a valve on a firebird I had to cut lines (fittings were rusted and wouldn't come loose) whicj ended up replacing all brake lines.  
thanks
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#4
Can any one verify if my master cylinder and proportional valve are correct?
My cylinder has lines on passenger side, the ones at cj pony have them on driver's side
My proportional valve is mouned to wheel well near fire wall.



[Image: IMG-3678.jpg]

image uploader

[Image: IMG-3677.jpg]
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#5
Should be on the driver's side. The combination (proportioning) valve appears to be correct.

Another potential place for the leak is in the combination valve. It's possible the previous owner removed the shuttle valve from the inside to keep that pesky brake light from coming on in the dash.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#6
(11-11-2019, 03:20 PM)Don C Wrote: Should be on the driver's side. The combination (proportioning) valve appears to be correct.

Another potential place for the leak is in the combination valve. It's possible the previous owner removed the shuttle valve from the inside to keep that pesky brake light from coming on in the dash.
Is the combination valve mounted in correct location?
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#7
That is for sure backwards, lol. Somebody went to a lot of trouble to do that.
[Image: DSC-0942.jpg]


When a man is in the woods and talks and no women are there is he still wrong??
Tongue
David
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#8
Yes, it looks like your combination valve is in the correct position and orientation.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#9
(11-11-2019, 03:20 PM)Don C Wrote: Should be on the driver's side. The combination (proportioning) valve appears to be correct.

Another potential place for the leak is in the combination valve. It's possible the previous owner removed the shuttle valve from the inside to keep that pesky brake light from coming on in the dash.
Don are you saying that the removing the shuttle valve would allow both bowls to empty when from lines where taken loose.  This is when fluid had drained onto floor.  If the shuttle valve was in place and in good condition wouldn't only the Large (front wheels) bowl empty??

Don, the master cylinder in your picture looks to be farther from fender than mine too.  Mine sits 6" from hood hinge pivot pin to side of master cylinder. 
 
[Image: IMG-3682.jpg]
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#10
Yes, the shuttle valve in good condition and in place would keep the rear brake reservoir from draining out of the front brake lines.

The location of your brake booster and master cylinder looks correct. Mine is out of the car, so can't measure mine. You can use the wiper motor in David's picture for a location reference.

Another possibility is that the master cylinder may have a hole in the web that separates the two reservoirs. If the seals are bad in the master cylinder piston the fluid could drain out, also.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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