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30.2 Clutch Master

Replacing the Master Cylinder
Year(s):  1980-1991
Model/Type:  Vanagon, All
Bentley Page(s):  30.2

From:  Jeffrey Earl

Symptom(s):  Fluid on carpet by driver's feet. Spongy Brakes

* Suitable Clutch Master Cylinder
* DOT-4 Brake Fluid, about a quart

* Assorted Metric Combination Wrenches
* Assorted Metric Sockets and Ratchet Wrench, with
* Torque Wrench: 0 to 25 ft./lbs
* Phillips Screwdriver
* Vaccuum-pump brake-bleeding kit
* 3-foot-square piece of plastic sheeting and some
ever-helpful duct tape: lay this down on your
carpeting to catch the inevitable spills
* A small inspection mirror and flashlight may help in
seeing what you're doing in the tight confines above
the steering column

Here's a simple homemade alternative to a store-bought
hose-clamping tool: cut a 1"-long section from a 3/8"-
or 1/2"-diameter wooden dowel, then split it down the
middle to form two half-round pieces. Tape these to
the jaws of your locking pliers and use this to
carefully pinch-off rubber hoses while you work on
related components. Not too hard though, or you'll
damage the rubber.

1) Start by collecting the necessary tools, parts, and materials, followed by some vigorous stretching exercises and calisthenics as taught by your junior high school Phys. Ed. coach; the clutch master cylinder in particular is very well tucked away beneath the dash and there is no comfortable way to work on it without assuming a variety of contorted postures and compromising positions.

2) I suggest you use ramps or jackstands to raise the rear of the Vanagon. This will later encourage the inevitable air bubbles in the hydraulic line to migrate back to the slave cylinder, where they can be bled out. Set the parking brake and engage the transmission in reverse or first gear.

3) Remove the shroud covering the instrument cluster, to gain access to the hydraulic fluid reservoir. Also remove the lower steering-column cover by removing the two screws and carefully wriggling it loose.

4) Lay down your plastic sheeting and tape it snugly around the steering column. Hydraulic fluid will infiltrate carpeting and dissolve paint, so do all you can to prevent it getting on bodywork. Use cold water or rubbing alcohol to clean spills from such surfaces.

5) Using the hose-clamping tool, gently pinch-off the braided rubber supply hose leading from the hydraulic reservoir to the front of the master cylinder (relative to the vehicle), then carefully wriggle the hose loose from its plastic nipple on the master cylinder.

6) From your new or old slave cylinder, borrow the rubber dust cap for the bleeder screw, and keep it handy. Begin loosening the pressure fitting on the metal high-pressure line exiting the back of the master cylinder, then remove the two retaining bolts which hold the master cylinder to its bracket.

7) Completely remove the metal line from the master cylinder. To prevent several ounces of hydraulic fluid from dribbling onto the floor, temporarily slip that rubber dust cap over the end of the line. By pinching off the rubber supply hose, and plugging the end of the metal line, you should have no more than a tablespoonful or so of hydraulic fluid to clean up. NOTE: Vanagons built prior to 1987 utilize a union-nut pressure fitting for this application, while later models use a bolt-through banjo fitting, with two copper washers. If yours uses the latter style, be sure to replace these washers when re-installing. Carefully lower the master cylinder from its place, being mindful of the pedal-actuated rod which will slip from the rubber boot atop the master cylinder.

8) Installation of your shiny new master cylinder is pretty much the reverse of removal, starting by carefully slipping the actuator rod into the master cylinder's rubber boot. After removing the rubber dust cap from the end of the metal line, you may find it easier to start threading the high-pressure union into the master cylinder if you do so before mounting the master cylinder. Tighten the master cylinder's mounting bolts to 18 ft./lbs, and the high-pressure line fitting to 12 ft./lbs..

Bleeding the Clutch Hydraulic System

Air will have been introduced into the system by now, and this will prevent proper functioning of the clutch mechanism, so it must be bled. Start by carefully topping-up the fluid reservoir in the dash with fresh fluid. Unlike the brake hydraulic system, the clutch evidently cannot be bled simply by pumping the pedal; the air bubbles will only compress and expand instead of being forced out, so Volkswagen specifies that a vacuum-pump-actuated bleeder be used. The Haynes manual states one CAN use the usual bleeding techniques, so who knows? I'm also told that one can simply leave the rear of the van raised and the bleeder screw left open overnight, allowing air bubbles to work themselves out, but I have not tried this method, and remain dubious.

I purchased a vacuum bleeder pump kit (about $40 in discount auto-parts stores), which can be used for both clutch & brake hydraulic systems, as well as testing vacuum hoses.

1) Atop the slave cylinder (ed note:There is no bleed valve on the master) is a bleeder screw, protected by the rubber dust cap. Remove the cap, loosen the screw 1/2 turn, and attach the hose of the vacuum bleeder, according to the bleeder kit's instructions.

2) Actuate the bleeder pump several times, until fluid begins to flow through the tubing and into the bleeding reservoir. NOTE: If the hydraulic fluid has not been changed in recent years, it will be dark or nearly black, indicating contamination by dirt and water; this is perhaps what caused your components to fail in the first place. Volkswagen (and most other auto manufacturers, for that matter) recommends brake/clutch fluid be replaced every two years. This is the same as the procedure outlined here but is considerably easier, as it does not necessitate the replacement of parts.

3) Continue drawing fluid until it is clear of dirt, moisture, and air bubbles, periodically pausing to check the level in the dash reservoir and adding fresh fluid if necessary. Do not allow this level to fall below the 'MIN' indicator, or air will again be introduced into the system, and you will have to start bleeding all over again. Remember, you've got about 10 feet of 3-4mm line to bleed, so this may take a full 12 oz. bottle or more.

4) When satisfied all the air has been bled from the system, tighten the slave cylinder bleeder and replace the dust cap. Fire up the engine and see if you can engage/disengage the transmission. If the gears clash or refuse to engage, you probably still have air in the line; re-bleed and try again. If all seems well, drive down off the ramps and take her out on the road to run through all the gears. You may find that within a couple hundred miles of driving over the next few weeks, the gears will begin to complain. This probably means you still have some air bubbles lurking in your line, so bleed again until it works right.

Check with your local municipality regarding the proper disposal of your used brake fluid. Mine requested that I add it right to my used motor oil and recycle it all together. Others may prefer that you keep the brake fluid separate from other automotive fluids and dispose of it as a hazardous material.

(The complete text of this posting, along with several illustrative photos, may be found in the Technical section of

See Comments on this entry (F.W.I.W.)

Clutch Master Cylinder Installation
From: Joel Cort
Year(s):  All
Model/Type:  Manual Transmission
Bentley Page(s):  30.2
Symptom(s):  Clutch not disengaging, Leaking clutch fluid by pedals

Date: Fri, 10 May 2002 20:22:08 -0700
Reply-To: Joel Cort
Sender: Vanagon Mailing List
From: Joel Cort
Subject: Re: Clutch Master Cylinder Installation Q:'s
Comments: To: Michael Nichols

This is a fairly easy job to do. It could get real messy if you allow the brake fluid to drain all over the floor board and carpeting.

To prevent that, what I did first was drain enough fluid from thereservoir on the brake master cylinder to go below the clutch master cylinder line level. - I syphoned it out but there are other ways.You can put a drain hose on the bleeder valve and open it draining all you can. You can also open the bleeder back on the slave cylinder and drain the entire system.

At this point pickup the John Muir book and read the part about getting in the back of the van with your loved one and relax.

Ok with most of the fluid sufficiently drained, loosen the line-out pipe to the slave cylinder. Place rags underneath and let it drain off any fluid. Place a container underneath to capture all the fluid that you can.

Have lots of rags handy under the brake pedal. Don't get any fluid onany paint it will eat it up. If you do spill use rubbing alcohol toclean it up quickly. I guess you better not be reading the Muir bookand smoking a dubby while doing this. It might scorch your van.

Ok back to the master cylinder: Ok disconnect the fluid line-out to the slave cylinder. Note the two copper washers. There is one on the outside and one on the inside of the hose connection. Loosen the two bolts that hold the master cylinder in place on the bracket. Now you can pull out the master cylinder and hold it inyour hands. At this time you can wiggle the main fluid hose coming from the brake reservoir and work it off the unit.

Clean up the area and you are ready to replace with the new one.Insert the brake fluid hose from the reservoir back on. You may use some silicone to get it on snug. No clamps required. If it is worn and cracked you may want to replace it as well.

Check that the plunger pin is well situated in the pedal mechanismrebolt the clutch master cylinder in position.rebolt the line out to the slave with one copper washer on each side of the bolt. You may need to replace those washers. And now you are ready to add new fluid and bleed the system.

Here is the trick. The slave cylinder is lower than the clutch master so all you have to do to drain the air out of the line is to open the bleeder on the slave, add plenty of fluid in the reservoir and wait. Let Gravity work for you. To quote john muir some more, relax and warm up with a friend.

Ok ok, you can help it along by pumping the clutch pedal. repeat until you feel pressure and the slave is moving the throw-out bearing.

I found out that it took about a week of driving to get the pedal adjusted automatically with the proper amount of free play so don't go trying to adjust the plunger or anything. Give it some time and it should adjust to the proper freeplay. If you can engage the gears and change them with little pedal play, that's OK it will adjust in time.

Another thing that happens about 6 months later or before this is the partner slave of the master goes out too. So might as well change both at the
same time and save the rest of the afternoon.

Good luck
89 Syncro Westy MV
Rochester NY.

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