A common complaint is a "spongy" brake pedal. Normally the pedal feels firmer and more secure, but now whenever pressure is applied to the brake pedal, it feels "mushy". The pedal may feel more like normal after repeatedly pressing and releasing it. However, the firmer feel quickly disappears after you take your foot off the pedal. The most common cause of a "spongy" brake pedal is air in the hydraulic system. This problem can be easily corrected by bleeding the brakes. Follow our Brake Bleeding Procedure and in all likelihood you’ll find at least one spit as the air escapes from the bleeder valve.
The wheels do not have to be off the ground to bleed the brakes. Our preferred method is to jack up one wheel at a time (securing it firmly on a jack stand) and remove the wheel so we don't have to crawl under the car to get at the brake bleed screws. You risk a face full of fluid too if you try to do it under the car. Use a small (7mm) box-end wrench (ring spanner) for this job -- it will usually grab the bleed valve okay even if some ham-fisted person has rounded the flats in the past.
Note: If someone has replaced the wheel cylinders in the past, the bleeder valves may be 1/4-inch rather than the metric size of 7mm. The valves may also require a smaller ID bleeder tube than the 7mm valves.
Bleed the longest lines first, working to shortest. On a left-hand drive car, this is right-rear, left-rear, right-front, and left-front; on a right-hand drive, it will be left-rear, right-rear, left-front and finally right-front.
Don't forget to check the fluid level in the reservoir frequently as you are bleeding the brakes and master cylinder -- running the reservoir dry will put air in the whole brake circuit and you'll have to start all over again.
Usually checking the reservoir fluid level after each wheel is enough -- unless you have A LOT of air in the system. Bleed till you see clean bright coloured (new) fluid coming from the bleeder valve. This will make the rubber portions of your brake lines last longer. Old fluid usually darkens with age, so it's easy to tell the new stuff when you see it.
It is important to replace the reservoir cap after each check of the fluid level. Brake fluid is hygroscopic -- it absorbs water rapidly. Water in the lines leads to corrosion and possibly boiling under heavy use. Also, cap the brake fluid bottle after each use for the same reason.
Note: There is a tiny pin hole in the reservoir cap to allow air in and out so that the brake fluid can expand and contract and move into and out of in the reservoir during braking. Make sure this little hole in the reservoir cap isn't plugged.
During the bleeding process it is best to close the valve BEFORE the assistant's foot hits the floor. This prevents his/her foot bouncing back and introducing air again. In other words, short squirts of fluid are best, rather than getting the last drop out of each stroke. If you release the fluid slowly, you could get more from each stoke without a 'bounce' problem. This technique allows for the use of even 7-year old or untrained assistants!
Arrange a 'code' with your assistant, so they don't release until you say so; e.g., 'foot down' and 'foot up, please' etc. Your assistant will need some patience too, it will take at least 3-4 pumps on each wheel to get bright new fluid through (could be more) and then the time necessary to replace that wheel and move to the next one.
At the end of the operation the correct level in the brake fluid reservoir is at the horizontal seam in the fluid bottle; i.e., about 3/4 full. Don't fill it completely, as it will expand in hot weather and cause the reservoir to overflow. Brake fluid is a very good paint stripper!
Use a quality fluid of course. It shouldn't matter if you use drum or disc fluid though -- disc fluid is designed for higher temps than drum stuff. If your Bug has disc brakes on the front, you will I have to use disc brake fluid, not drum brake fluid -- but it will work equally well for both. You'll probably need a pint or so of brake fluid for this job.
After completing the brake bleeding operation, check the pedal travel. Badly adjusted brake shoes may have been disguised by air in the lines. The pedal should go hard in the first half of travel, not down near the floor. If you do have to adjust the rear brakes, check the hand brake adjustment too.
And while you are checking the brake shoe condition (e.g, for thickness, any brake dust) have a good look at the slave (wheel) cylinders for signs of wetness, which would indicate that the wheel cylinder is leaking.
Some people use a suction pump, trying to make the task of bleeding the brakes easier and do-able by just one person. We found that the “handy-dandy” vacuum pump is anything but, and reverted to the old-fashioned way. The problem we had was with air being sucked into the bleeder line so that we couldn't tell when we were done!
We finally determined that we was unable to get a good seal at the point where the bleeder hose attaches to the bleeder valve, and the vacuum pump was sucking air at that point, making it impossible to tell whether the air was coming from the system or was leaking into the bleeder hose at the connection point. When bleeding the brakes the old-fashioned way, with an assistant manning the brake pedal, the fluid (and any entrapped air) is forced out of the system by pressure on the brake pedal, so air in-leakage at the connection point is not a problem.
Someone reported that during an attempt to bleed the brakes no fluid or air came out of the bleeder valve when pressure was applied to the brake pedal and the bleeder valve was opened. Such a situation may be caused by several things -
Disclaimer stuff: Rob and Dave have prepared this information from their own experiences. We have not assumed any specialised mechanical knowledge, but we DO assume that anyone using this information has at least some basic mechanical ability.
We hope you find this information useful, but we don't take any responsibility for anything which happens to you, other people, your VW or any other property or goods resulting from your use of this material.
Feel free to print off any of this information for your own use. If you intend to link this material to another site, reprint it, or in any other way redistribute it, please leave the information complete, including this disclaimer section, and provide a link to this Web site.
Last revised 3 August 2004.
