Clutch Master Cylinder Replacement

APPLICATION: All US-spec Vanagons 1980-1991.

TOOLS NEEDED: Ratchet with 13mm socket and extensions; 13mm wrench; 12mm wrench; 7mm wrench; length of hose that will fit over the bleeder valve on the slave cylinder (windshield washer hose from an air-cooled Volkswagen fits well); glass jar; brake fluid (a lot!); lots of rags and some kind of small pan for catching brake fluid; a helper; jackstands; lug wrench; wheel chock; torque wrench if you've got it; some type of siphon (a dropper will work well).

As a first step, remove the instrument cluster cover. It just pops off. Then remove the plastic film that covers the instruments. Remove the brake fluid cap and use your siphon to withdraw brake fluid from the reservoir and squirt it into your jar. You will see that there is a hose that takes off from the side of the reservoir. This is the hose that supplies the clutch master cylinder, so try to get the brake fluid level below that point if possible.

Once you've done that, it's time to prepare for removing the master cylinder. Pull the carpet under the pedals back so that the floor of the van is exposed. Then stuff lots of rags in there and if you have a pan that you can get under there where fluid will drip, go for it. Stuff LOTS of rags in there. I'm not kidding. That supply hose is pretty big and you're going to get a lot of fluid out. You don't want to get the fluid on painted surfaces as brake fluid damages paint.

OK, first removal step is to undo the hydraulic fitting that goes to the slave cylinder. It's the one immediately below the two mounting bolts and it looks like a brake line connection. It takes a 12mm wrench on the nut and it will loosen. As you loosen this, fluid will begin to drain out so make sure it's draining onto the rags or into your pan. I loosened mine so I got a steady thin stream, so that way I could direct the flow rather than opening it all the way and having it all gush out at once. Once the flow stops, you're probably not going to get any more fluid out, so go ahead and loosen the nut all the way so the fitting is disconnected from the cylinder.

Now you want to loosen the two master cylinder mounting bolts. They are both 13mm and I seem to remember that one is easier to undo with a ratchet while the other is easier to undo with a wrench. Do what works for you. Loosen the bolts and then remove them and put them in a safe place.

Now the master cylinder is almost ready to come out. Pull it down so that it clears the pushrod (which remains attached to the clutch pedal) and then pull it out toward you so you can remove the supply hose from the fitting on the rear of the cylinder. Be careful because the fitting on the cylinder is plastic. Try not to break it off inside the supply hose. Mine came off without any problems.

OK, now you have the old clutch master cylinder out. That wasn't too hard, was it? :-) Now you are ready to put the new one in. Remove the plastic caps from all the holes in the new cylinder, there are three. Now attach the supply line to the new master cylinder, then find the pushrod (hanging above where the master cylinder was, you will have to reach for it by feel). Guide the pushrod into the hole in the rubber boot as you move the master cylinder into position. When you get it into position, install the two mounting bolts, but very loosely. You want to install them loosely so it will be easier to install the hydraulic fitting to the mastery cylinder.

Now install the hydraulic fitting to the master cylinder. You will likely have to hold the master cylinder in position with one hand while threading the nut into the master cylinder with the other. You want the nut to thread in as straight as you can get it or else it won't want to start on the threads. Once you get it going, continue to tighten it up and then use the wrench to tighten it further. Don't make it too tight as you will likely have to loosen it shortly.

Now tighten the mounting bolts down fully. You're done with those. OK, now remove the hubcap from the left rear wheel and then crack the lug nuts loose. Chock the front wheels and then get the rear of the van up on jackstands and remove the lug nuts and the wheel.

If your helper is hanging out, now's where he/she comes in. Arm your helper with a big can of brake fluid, a rag, and a funnel if he/she is pouring-impaired. The first thing you want to do is do an initial bleed of the master cylinder, as you're never going to get any fluid through there with that huge air bubble that's in there now. First, top off the brake fluid reservoir. Then have your helper monitor the fluid level while you go down to the master cylinder with your 12mm wrench and a pan to catch fluid or a lot of rags or both.

What you want to do is loosen the hydraulic fitting on the master cylinder enough for fluid to flow out when you push on the clutch pedal. You won't have to loosen it much. Loosen it a couple turns and then push on the clutch pedal and watch what squirts from the hydraulic fitting. It will likely be a little fluid with lots of air in it. You may note a large initial drop in the fluid level in the reservoir the first time you do this, so make sure your helper is paying attention. Make sure he/she doesn't let the fluid level get below the take-off for the clutch supply line. While you still have the pedal held down, tighten the hydraulic fitting, then let up on the pedal.

Repeat this action until you are getting fluid only from the fitting, with no air bubbles. You have then just bled the master cylinder. Now you have to bleed the whole system at the slave cylinder.

Give the driver's seat to your helper and have him/her leave the door or window open so he/she can hear you. Go to the left rear, and crawl in the wheel well. Find the slave cylinder, you'll be looking right at it with that wheel removed. The bleeder valve is right on the top, protected by a dust cap. Remove the dust cap but don't lose it! Then get your length of hose and fit it securely over the bleeder valve. Make sure it fits tightly, you want an airtight seal between the bleeder and the hose. Now pour new clean brake fluid ONLY to cover the bottom of your clear glass jar and then submurge the other end of your hose in it, and KEEP IT SUBMURGED at all times throughout the bleeding operation.

OK, get comfortable because you'll be there for a while. Have your helper push down on the clutch pedal and hold it. Then loosen the bleeder valve a half-turn or so with your 7mm wrench. You won't need to loosen the valve much, but if you notice you're not getting much flow, loosen it a bit more. You should be getting a pretty good flow. As long as you keep the hose submurged in your glass jar, you can leave the bleeder open throughout the operation. When you open the bleeder, you will probably see some air bubbles come out of the hose in your jar. Have your helper let up on the pedal and then push it out again, and you'll see more bubbles and probably some cruddy old brake fluid. Yuck! You're basically going to keep repeating this procedure until you are getting nothing out of the bleeder valve but clean new fluid with NO bubbles. Try some variations on pumping the pedal too, as that seems to work some more bubbles out. Try full strokes of the pedal, try light partial presses followed by full strokes, etc. It also seems to help if you do a few strokes, then let it sit for a couple minutes, then do another full stroke. You will probably notice a lot more bubbles coming out if you do it that way.

MAKE SURE your helper is keeping an eye on the fluid level. Don't let it get below the supply line take-off or you'll have to start over again with bleeding. When we did it, we went through a whole 32-oz. can of brake fluid plus a couple smaller cans we had laying around. Don't be surprised if it takes a long time. It's a large-diameter line and it's about 15 feet long. And when you think you've got it bled, do 5 or 6 additional strokes just to make sure. It almost had us fooled a couple times and then, surprise!, more bubbles. If you have to dump out your glass jar during the procedure, make sure that you close the bleeder valve on the slave cylinder while your helper is holding the pedal down BEFORE you take the hose out of the brake fluid.

Likewise, when you are ready to start again, first put the hose under the new fluid in your jar, then have your helper press the pedal down and hold it, then open the bleeder. Order of operations is important here. You don't want any air being sucked into the system. Once you are confident you have the system bled, then close the bleeder valve while your helper holds the pedal down. Then, since you are familiar with how the clutch pedal should feel, climb in the driver's seat and try it out. It should feel fairly firm, not spongy. Since you have the rear on jackstands, start the engine and try shifting through the gears. The clutch should disengage completely and there should be no grinding as you move the shifter lever into gear with the clutch pedal depressed. If the pedal feels spongy and there is gear-grinding, then go back and bleed it some more until you resolve that problem.

Once you've got it bled, clean up your work area. Remove the hose from the slave cylinder and replace the dust cap over the bleeder valve. If you've spilled brake fluid anywhere, especially on anything painted, wash it off with cold water. Put the left rear wheel back on, hand-tighten the lug nuts, and get the van down off the jackstands. Once it's back on the ground, torque the lug nuts to 125ft-lbs. (that's the spec for my '81 anyway). Replace the carpet under the pedals, make sure the brake fluid level is up to the max line on the reservoir and don't forget to remove your front wheel chocks!

Put the plastic cover and instrument panel cover back over the instrument panel, put all your crap away, dispose of your brake fluid properly, and put your hubcap back on, then go for a test drive and make sure the clutch is working like it's supposed to. Do NOT re-use any of the brake fluid you got out of the system while bleeding. Only put clean unused brake fluid into the brake fluid reservoir, and only if it's from a sealed container. Brake fluid readily absorbs moisture from the air and this moisture can boil if the fluid gets hot enough, leaving you with no brakes.

Not too bad a job. The most time-consuming part of it is the bleeding, and it's not difficult, it just takes a while.

Sean Bartnik
January 15, 1998

Back to the tech page.