I need help

[flaboy]

had to replace the master cylinder on my ITC rabitt(1980), it was not holing presure,soft pedal until it was pumped a few times.Now the brake peddle won't get very hard.Car stops,but locks up easy in the rear.I'm not the smartest guy when it comes to cars,but this just doesn't seem right.Going to the school in south carolina in a week so i need to get it fixed in a hurry.I've bled the brakes and nor more air is comming out.any ideas??

Thank you for any help and advice.

Tim

 

[Bill Miller]

Tim,

VW brakes can be pesky to bleed. Also, was it a brand new m/f or a rebuild? Are you sure the front seals are good? Was it the same m/c as was in there before? You also might have a bad/stuck proportioning valve.

 

[Bildon]

>>had to replace the master cylinder

You may need to bench bleed it. This requires some tubes and plastic fittings that screw into the MC ports.

If you dont want to take it back off...Jack only the front up... loosen the lines to the MC (or take them off) and push the pedal back and forth slowly while tapping the MC with a big wrench or small pein.

 

[racer14itc]

I ran into this on my ITC car and the solution is to bleed both pistons on the master cylinder at the same time. If you only do one corner at a time, the piston cannot make a full displacement becaust it is stopped by the other piston since it's still sealed. If the brake line circuits are still stock (i.e. diagonal braking), you can do BOTH fronts at the same time, and this will allow full travel of the pistons. More than likely this will expel any air hiding in the master cylinder.

This also applies to dual master cylinder setups like a Wilwood balance bar setup. I've known many racers who've almost come to grief trying to bleed these setups with the "conventional" method, and not being able to purge the air from the system. As soon as I tell them to do BOTH master cylinders at the same time (i.e. one front and one rear), VOILA! problem solved!

Here's an unsolicited tip for bleeding the brakes by yourself without a "Mityvac" or expensive vacuum bleed system. This assumes the car is up on 4 jackstands, wheels off, ready.

1. Get two plastic coke bottles, poke a hole in the cap and insert a long length of aquarium tubing.
2. Put the tubing on the bleeders on one front and one rear brake, and put the coke bottles on the floor beneath the calipers.
3. Open both bleeders and allow gravity to begin to force some fluid out of the bleeders.
4. Push the brake pedal to the floor, and jam it there with a broomstick or long rod of some sort. I use one of those adjustable "cargo bars" used to keep stuff from flying around the bed of the pickup truck, and adjust it to length so that I can jam it into the seatback and hold the pedal on the floor.
5. Close both bleeders.
6. Remove broomstick/rod and let the pedal come back up. Pump it (slowly) a couple of times to make sure it has released fully and re-filled the master cylinder pistons with fluid.

Repeat steps 2-6 several times until the fluid is clear/new and is free of any air. Make sure the bleeders are CLOSED before you release the brake pedal, or you'll suck air back into the calipers and have to start all over again.

I've been doing this for nearly 10 years, and it works. This way I don't have to have a helper in the garage to bleed the brakes.



MC

 

[rmicroys]

Even 'bench bleeding' a M/C on a car is relatively simple. I've done it on a few cars - but messy. I just undo all the lines right off the master - and with finger tips, plug all the holes. put a bunch of rags under the m/c to catch all the drippings, and have a friend pump the brake pedal a few times. All the ports will bleed. Don't keep your fingers in the ports too tight or else the fluid will spray everywhere. Then when the pedal is down - push your fingers in the ports good so that air doesn't get sucked back in when the pedal goes back up. Oddly enough, this is the Factory Service Manual recommended procedure on my old '95 Nissan 200SX SE-R. Works fine on most cars.