weird brake problem
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Cargo Master
Joined: Aug 2008
Posts: 2,661
Likes: 23
weird brake problem
My brother has a '69 Bronco.
For some reason about 1 out of a 100 times you use the brakes, it acts like there is air in the lines. Touch them again and it's just fine. Doesn't do it twice in a row no matter if it's been sitting since the last or whatever. It acts like air in the lines, but what confuses me is the way it just pops up every now and then. It's been getting slowly worse (maybe 1 out of 50 in the past month), so I'm guessing either more air has snuck in or it's moved it's way up the line.
It just seems odd to me. A piece of tube was replaced over the rear axle, so I'm guessing that's where the air got in, I'm assuming it's a tiny, tiny leak that just built up but what's odd about it to me is it's literally like 1 out a 100, where if it happens it doesn't happen again for about 100 uses of the brake.
Ideas? Smart fixes?
Thanks
For some reason about 1 out of a 100 times you use the brakes, it acts like there is air in the lines. Touch them again and it's just fine. Doesn't do it twice in a row no matter if it's been sitting since the last or whatever. It acts like air in the lines, but what confuses me is the way it just pops up every now and then. It's been getting slowly worse (maybe 1 out of 50 in the past month), so I'm guessing either more air has snuck in or it's moved it's way up the line.
It just seems odd to me. A piece of tube was replaced over the rear axle, so I'm guessing that's where the air got in, I'm assuming it's a tiny, tiny leak that just built up but what's odd about it to me is it's literally like 1 out a 100, where if it happens it doesn't happen again for about 100 uses of the brake.
Ideas? Smart fixes?
Thanks
Cranky Old Guy
Joined: Mar 2008
Posts: 3,562
Likes: 6
From: Raphine, Virginia
I'm assuming it still the stock brake setup. It could be about anything. Pinhole leak in rusted lines, wheel cyl, master cylinder, rubber hose collapsing etc. It would be best to go over the whole system. If the fluid is brown instead of clear it's time to change that. Of course once you start messing with brakes it compounds real fast. Bleeders break off when trying to get loose etc. If you decide to change the fluid, make sure all the bleeders will work before you start. The fact that it's slowly getting worse is that they may fail him when needed the most.
Logistics Pro
Joined: Nov 2009
Posts: 3,885
Likes: 12
From: Lawrence Swamp
go over the whole system
2X Richard...'what he said'. Does it have power brakes (not oe in a '69)?
If it wasn't a slo leak I'd say park it on "a surface" so U could check for b. fluid leaks (may wrk w/this 1 2?) n pump em, leave there all the time, etc. Ck "the surface" for signs of leaks...
Surface: clean cardboard, lght colored sheet, newspaper (either weighted down w/rocks), clean concreet...
Even pump em w/the MC cap off & look 4 bubbles while doing so (2 guys)...
Richard has the real answer. Let us know how U do, good luck.
2X Richard...'what he said'. Does it have power brakes (not oe in a '69)?
If it wasn't a slo leak I'd say park it on "a surface" so U could check for b. fluid leaks (may wrk w/this 1 2?) n pump em, leave there all the time, etc. Ck "the surface" for signs of leaks...
Surface: clean cardboard, lght colored sheet, newspaper (either weighted down w/rocks), clean concreet...
Even pump em w/the MC cap off & look 4 bubbles while doing so (2 guys)...
Richard has the real answer. Let us know how U do, good luck.
Elder User
Joined: Oct 2005
Posts: 677
Likes: 0
I agree with chrlful and gfw... go over the system.... and dont replace until the problem is fixed.... but it could be a bad master cylinder... when the seals in the master go bad... fluid moves past the plunger, so the brake pedal goes soft.... but not always....
I just swapped out one in my 79 F150 today.... it was a little different... but mostly the same.... it started under pressure with the pedal dropping in an inch, and then turned into not much pedal when you first engage the brakes.....
But check everything first..... rule out bad hoses, or air in the lines....
I just swapped out one in my 79 F150 today.... it was a little different... but mostly the same.... it started under pressure with the pedal dropping in an inch, and then turned into not much pedal when you first engage the brakes.....
But check everything first..... rule out bad hoses, or air in the lines....
Moderator
Joined: Aug 2002
Posts: 6,099
Likes: 379
From: Southern California
Additionally, if you can't find the leak, find a mechanic that has a brake bleeing system (not a hand pump type) but a real pressure bleeder...it will either find it or push the air out of the line during bleeding.
New User
Joined: Apr 2011
Posts: 6
Likes: 0
From: SE New Mexico
The problem is one of two. If it was the second one, you wouldn't have any breaks with the stock settup. I am pretty sure you have the single master cylinder. Its in the rear, I can almost guarantee it! The problem with this is, its hard to determine the side.... With this small of a leak, have a friend stand behind the rig on loose gravel, and see which rear wheel locks up first. Then you can go from there....... The other posts have it down, but this will help limit the side. Dont get a crosseyeyd friend, it is pretty close on most occassions....
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