Related Topics:
Hydraulic Clutch System Overview
Clutch Master Cylinder Replacement
Clutch Slave Cylinder Replacement
After replacing any clutch hydraulic components, air will have been introduced into the system, 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 which can be used for both clutch & brake hydraulic systems, as well as testing vacuum hoses.
- Atop the slave cylinder 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.
- 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, as outlined here.
- 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. - 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.
Even if you have failed during this process to keep the fluid level in the reservoir topped-up, as long as you haven’t depressed the brake pedal air should not have been introduced into the braking system, so the brakes will not need to be bled. However, if the fluid is more than two years old, and since you’ve already gotten your tools dirty and probably stained your pants, now would be a good time to bleed your brakes.
The clutch slave cylinder on my 1982 Westfalia is mounted above the transmission, and is not accessible from the top of the engine compartment. Access to the slave is only from below the van.
Carl yes, the clutch slave cylinder of every Vanagon I’ve seen is mounted to the upper, drivers side of the transmission & clutch bell housing, as seen on Page 30.2 of the Bentley workshop manual.
As seen in my photos, I’ve always found it easiest to see and access the slave cylinder by reaching forward from the open engine compartment, but I suppose one could also do so from beneath the van. Of course, disconnecting the rigid hydraulic line and using the bleeder screw really must be done from above.
Good luck on your project!
Great website, and thank you so much for taking the time to put all this information out there. It sure does help to have pictures, links, and awesome first hand knowledge. Thank you for helping with our 1984 heirloom!
Thanks for checking in, Kyle! Hope these tech/mechanical write-ups help.
I have tried this vacuum bleeder method and it was not effective. I have heard of a reverse bleed method where you connect the rear left drum bleeder to the clutch slave bleeder and you pump the brakes. Apparently it is very difficult to get air out of the clutch hydraulic line moreso than the brakes due to the size of the line. You end up fighting the air bubbles making its way back toward the clutch slave every time you pump the pedal and it gets trapped downstream of the clutch slave and can’t push it’s way past it. So the theory is that you have to pressure bleed the clutch slave in reverse so that you can push the air bubble back to the reservoir. Have you heard of this?
Sorry correction to this line “You end up fighting the air bubbles making its way back toward the clutch slave every time you pump the pedal and it gets trapped downstream of the clutch slave and can’t push it’s way past it.” If should read “You end up fighting the air bubbles making its way back toward the clutch slave every time you pump the pedal and it gets trapped downstream of the clutch MASTER and can’t push it’s way past it.”
I have not heard of that technique. I have also never attempted to reverse-pressurize the clutch or brake systems, and I am not sure whether it is possible, or whether it could possibly damage the master cylinders.
Generally speaking, whichever method you choose, I would advise raising the end of the vehicle to which you are trying to bleed, to encourage any air bubbles to rise to that end. So, if pumping from the front and bleeding at the rear, raise the rear; and vice versa.
While using a vacuum bleeder on the clutch slave cylinder, it can help to have an assistant gently pump the clutch pedal, and to make sure the reservoir remains full to the mark.
Another method I’ve used for solo work is a Pressure Bleeder like this one:
https://amzn.to/2GPV90x
This pressurizes the entire brake/clutch fluid reservoir and allows you to simply bleed each wheel and clutch cylinder until fluid runs clear, then disconnect the pump.
Have you ever replaced the METAL line from front to back ? At that rear T in the brakes, it had rust in just a few spots and it leak, you hit the pedal and heard SQUISH, just finished that job, but while under there, I noticed the metal line feeding the rubber flex line on teh slave, does not look great and might be just as rusty as the brake lines…looking for a smart way to fix or it’s dropping the gas tank a 4 or 5th time… thanks
I cannot recall the last time I replaced one of those long main lines, nor whether it was necessary to remove or partially lower the tank.
Here’s a good discussion on the topic. Also keep in mind that it’s easier on the 2WD Vanagons than the Syncro models.
Good luck!
Replaced my brake lines months ago and have been having trouble getting into reverse and first. I never bled the clutch. Sooooo much air was in there. Thanks for the procedure!