Brakes Cutting in and out

[eddyhead]

Hello,

I tried doing a search and couldn't find this issue but please let me know if this has been discussed.

I have a Rail and been having issues with my brakes recently. When the Rail is off I press the brake 1/4 way down and the pedal becomes hard as a rock. While the rail is running I get scenarios all over the place.

1. I can pump it and get full pressure after 2nd/3rd pump
2. I can press it to the floor and barely stop
3. the most recent was I was driving went to press the brake and the pedal went straight to the floor with no pressure and had no brakes at all. (Thankfully I was not at an intersection) After stopping I started to travel again and had brake pressure again.

Does this sound like a Master Cylinder Issue? or simply just need bleed?

[Q-Dog]

Sounds like it is time for a complete inspection of the entire brake system.
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Brian

'69 Dune Buggy
'69 Beetle Convertible
'70 Beetle

[Dale M.]

Since you probably do not have power brakes I would guess when you say "running" do you mean in motion....

Generally there is two things with brake pedal going all the way to floor, 1> system needs to be bled, 2> master cylinder going bad...

Air in line usually means a spongy pedal, radical changes in braking for rail sitting still vs in motion would indicate something with one or both wheel cylinders)...

Time to take things apart for inspection...

Dale
_________________
“Fear The Government That Wants To Take Your Guns" - Thomas Jefferson.

"Kellison Sand Piper Roadster" For Street & Show.
"Joe Pody Sandrover" Buggy with 2180 for Autocross (Sold)
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All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ...

[Bakerby]

Another possibility which happened to me is brakes have not been adjusted correctly i.e. Only 1 shoe on each wheel, this can allow for a lot of slack in the pedal before brakes kick in but when pumped up seem ok. Both shoes need to be adjusted equally.

[eddyhead]

I Spoke with the Company that makes my Pedal Assembly to make sure I was buying the right Master Cylinder rebuild kit. Thankfully he knew a lot about Buggys/Rails and we spoke for awhile and he suggested that if I get brake pressure sometimes and not others then that does not sound like a Master Cylinder. He suggested to check my wheel bearings, if these were going bad this movement could kick the pads back and why I Lose Brake but then shortly after get it back once i pump the pads back in place a couple of times.

I jacked up the Rail and the wheels did not have a lot of free play as I have experienced with bad bearings so I don't think that was the issue. Looking back on when I lost Brake was right after I was doing a bunch of doughnuts in the back yard. I went to press the brake and nothing, after i stopped and started back up again this time I had more brake pressure.

Last night I did a bunch of Straight line runs in the back yard and tried different braking pressures (Stomp on it, slowly press into it, etc..) and after 20 times I never had loss of Brake pressure, so I am thinking playing around in the yard pushed the pads and it just required me to pump them back in place.

I am going to Replace pads (They need it) and Bleed the system and go from there.

[TDCTDI]

If your wheel bearings aren't loose, then there isn't any play to spread the pads. A brake pedal that drops to the floor occasionally is indicative of a bad seal in the master cylinder. A low pedal that can be pumped up is an indication of a leak in the system, mal-adjusted shoes, or possibly brake pads that have been depressed by excessive play in bearings or severely warped rotors.

DO NOT shrug it off since it only happened once or twice, the system needs to be thoroughly inspected by someone that knows what they're doing.
_________________
Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.


GOFUNDYOURSELF, quit asking everyone to do it for you!


An air cooled VW will make you a hoarder.


Do something, anything, to your project every day, and you will eventually complete it.

[Axitech]

A warped rotor will kick the pads in and give you a low pedal that pumps up.
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[eddyhead]

[TDCTDI]

A bad seal on the piston in the master cylinder would allow fluid to return to the reservoir. The symptoms of this are as you describe your brakes, an occasional sudden drop of the pedal or even a slow drop of the pedal that returns upon pumping the brakes. Eventually it will fail completely, definitely not a good situation, especially if it’s a single circuit system.
_________________
Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.


GOFUNDYOURSELF, quit asking everyone to do it for you!


An air cooled VW will make you a hoarder.


Do something, anything, to your project every day, and you will eventually complete it.

[eddyhead]

What about a residual pressure fitting? Spoke with someone who said they have heard about this issue since the Ghia calipers have the 4 pistons, they would have to to pump or "prime" the calipers before stopping. They Installed residual pressure fitting which holds 2lbs of pressure and keeps the calipers primed.

Anyone else have these?

[cbeck]

4 wheel discs. Put 2 psi valve on the rear only per advice from the flaps I bought the brakes from.
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My cut in half and rebuild thread
www.thesamba.com/vw/forum/viewtopic.php?t=647779