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Brake master cyclinder

Brake master cyclinder replacement procedures
From: Joel Cort
Year(s):  All
Model/Type:  Vanagon
Symptom(s):  Brake fluid on floor, poor brake action.


To replace the brake master cylinder in a Vanagon:
Tools needed:
Phillips #2 and several flat screwdrivers
7mm wrench to loosen and tighten the brake bleeder
13 mm socket/ratchet with 9" extension (Torque wrench
optional)
11 mm open end wrench for the brake line
22 mm and 24mm wrench or socket to remove or replace the
brake light switches (or one big cresent wrench)
Supplies needed:
2 pints of DOT 3 or 4 brake fluid
Rags
2 pints of rubbing alcohol
Silicone spray lubricant (optional)
brake cleaner spray (optional)

Step 0. Disconnect the battery ground terminal.
Step 1. Remove Instrument Panel:
I pulled off the cover over the instrument cluster. Then the 4 Philips head
screws. Next reach behind the Speedo cluster and squeeze the plastic
retainer holding the cable in and release that. This gives you more play in
the instrument panel to unplug the main cable cluster. To be safe you
should disconnect the battery when playing with the wiring. I then pull all
switches/plugs and wiring - fairly straight forward and easy. With all that
stuff out of the way the MC is sitting there with the plastic filler tank
taking up most of the space. I also disconnected the low fluid sensor wire
on the MC filler cap.

Step 2. Check for similarities with the new one:
Ok double check that the two MCs were real close in appearance. The new one
must have all the plugs and ports in the same location to route the brake
lines and the filler tank. The part in your hand may not fit your van.

Step 3. Drain the filler tank of all the brake fluid:
First you have to drain as much the brake fluid out as you can out of the
plastic container and MC. I put a hose and bottle on the bleeder on the
left front caliper and open the bleeder while pumping the brakes. This
worked well and drained all the fluid out.

Step 4. Remove the Clutch MC filler tank hose: (If you have a manual Vanagon)
On the upper right side of the tank there is a pipe leading to a fitted 3/8"
braided rubber hose going to the clutch master cylinder that needs to be
worked off. Put a rag under to collect any fluid here. I used a pair of
pliers to gently start twisting the hose and sprayed some silicone spray
lubricant. I then used several screwdrivers to pry it off and finally my
twisting motion to work it off. Be careful doing this because if it breaks
the plastic pipe you will need a new tank. Once I had the rubber hose
removed I plugged it up to prevent any brake fluid from leaking out while I
was working in there.

Step 5. Remove the brake lines:
Have a rag under both of the brake line to catch that little drip. If you
pumped the fluid out there should be minimal amounts easily captured on a
rag. Loosen the two metallic brake lines going to the front and rear brake
circuits. One brake line is on the center right side blocking the anchoring
nut so you must remove the brake line. I believe the brake line nuts are
11mm. The other brake line is on the end of the MC and sticking out at you.
The real pain was holding a shop light in there there's no good hook.

Step 6. Loosen and remove the brake master cylinder:
Ok two brake lines off, rubber hose off, all you have left is the two MC
anchor nuts. I believe they are 13mm. They are not supper tight and loosen
out easily. I used a magnet wand to capture the loose nut and washers. The
MC is now ready to be removed. Jimmy the MC to disconnect the brake light
wiring from the two switches on the bottom and VOILA!

Step 7. Prepping the new MC for installation:
Switches
OK now you have the old one out and you can compare it to the new one. My
new MC came with the two new brake light switches but I ended up
using my old switches - 22mm wrench on my old ones 24mm on the new ones.
The new MC switches had 3 male plugs and my old ones had 2 male at a
slightly different offset. So rather than dicker with the wiring plug I
changed the switches. Be careful to put the switches in the correct
threaded hole on the MC.

Filler tank
The plastic brake fluid tank comes out of the MC easily by prying it out of
each rubber grommets. Mine was full of 108K miles of brake line crud so I
cleaned it out. Regular rubbing alcohol works really well to break down
brake fluid. I swished alcohol around in the baffles of the filler tank
several times and it is as good as new. The new MC came with new grommets
so I just applied some silicone to ease it in. It snapped right on the MC.
OK double check everything making sure there is a new seal between the MC
and the brake booster (which came in the box with the MC).

Step 8. New MC installation:
This is where Bentley and Haynes drop off and tell you to do it all in reverse order.
Angle the new MC with the tank assembled and place it on the pushrod coming
out of the booster. You can press on the brake pedal to see the rod to get
a better angle at it. *** Scott Foss sez 'I put the tinest dab of grease on the tip of the rod coming out of the brake booster.. I don't want bare metal-to-metal contact where the rod pushes on the cylinder in the MC'*** Ensure that the pushrod inserts into the MC shaft. I used the same lock-ring washers and nut although two new ones were also supplied. I used a magnetic wand to place the washers and nuts on the threads in the tight area. Leave these nuts loose until you get the brake lines threaded. Refit the brake line circuits ensure that the threads are aligned and tighten down. Refit the braided rubber hose for the Clutch MC. Torque the MC down to the right Nm from Bentley.

Fill with new brake fluid (I used DOT 4) and pump the brakes a few times to
get the juices flowing
Step 9 Bleeding the air out of the system.
It is absolutely imperative to get all the air out of the brake circuit. Otherwise the brakes will be mushy and not operate efficiently.
To bleed the brakes, you need an assistant, a buddy, or one of your kids. Kids usually whine and complain and get tired real fast.
OK so you want the buddy to pump on the brake pedal while you lay under the van and open and shut the bleeders at each wheel cylinder. Usually three action of the pedal (pump) and final pressure while you open the bleeder works real good. You have to do all the bleeder, starting with the furthest distance, so the right rear, then the left rear and the right front and finally the left front. The pressure mounts after each bleeding and repeated pumping until it is optimum.
Repeat the process once you have cycled through each bleeder. Watch the fluid level in the plastic tank to ensure continuous level of brake fluid and not introduce air to the circutit.
======
So at the rear wheel bleeders, loosen the bleeder. Be cautious not to break the bleeder. Some wheel cylinders are so darn old that this is one crusty rusty mess and the little bleeder nipple snaps. If this is the case you will need to either get a new bleeder installed or replace the entire wheel cylinder.
======
This is additional work to say the least that you were not planning on. You have to remove the brake drums on the rear, the brakes the springs to get to the wheel cylinder again consult Haynes or Bentley for information. You may feel screewed by then, so in reference to keeping your VW alive from the old days, go get a cold one and regroup. You are not totally screewed but the job just became bigger. I guess you should try to loosen the bleeders as the very first thing before starting this job so you can guage how much of a jot it is or many more parts you are going to need from your favorite list vendor.
===============
Some early Vans had dual front bleeders for both brake pistons. Ensure that you bleed both pistons. I think the models after 86 came with a single bleeder.







Step 10. Cleanup:
Hopefully you've made it through the bleeding without leaving blood, sweat or tears. You are done. So you see this is one of the easier jobs. If you do spill any fluid use some rubbing alcohol or brake cleaner to clean it up and mop it up. Alcohol will work on the carpeting also to dissolves the dripped brake fluid. If there is any on the metal surfaces, it will eat the paint and leave bare metal ready for the rust to attack.
Good Luck - Hope this helps
Joel



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