Saturday, December 23, 2006

VW - TULZ Part Five

TULZ – Part Five

Gimme a Brake

Howz yerz? Brakes, that is. Block your wheels with something then jump in, release the parking brake and step on the brake pedal. How far down does it go? How far down SHOULD it go? (See the manual.)

Set your parking brake. No, do it again, this time counting the clicks. How many clicks? Make a note of that. Now step on the brake pedal again. How far down did it go with the e-brake set?

How'd it feel when you stepped on the brake? Hard is good. Springy, spongy, bouncy is bad; spongy brakes means there is air in the system; they need to be bled.

You need to change your brake juice every two years, more often if you live in a damp climate. If you haven't done it, go do it. And if you've just bought this wreck, do it anyway… the last guy probably didn't change it either. Brake fluid is hygroscopic; it absorbs moisture from the air. The brake fluid reservoir is open to the atmosphere. Every time you step on the brakes the level of the fluid goes down then comes back up. That slight up & down motion makes a very effective air pump. And the fluid absorbs moisture from the air (didn't I just say that?)

Changing your brake fluid every two years is vital because the master cylinder and wheel cylinders are made of cast iron, which loves to rust. Replacement of the master and slave cylinders on a Volkswagen is almost always due to 'pitting'. And it is plain old-fashioned RUST that makes the pits. (Modern vehicles use aluminum brake cylinders and some use synthetic brake fluid that isn't hygroscopic.)

Even though bleeding your brakes is very easy, you have to get to the backside of the wheels to do it. If the only way to do this on your vehicle is to jack it up that puts the task into the 'Major Repair' category, not because of its difficulty but because of the hazard. Any time the vehicle's wheels are not on the ground and you have to work under it, you must support the vehicle with jack stands. Major Repairs should be done in the company of another person. They don't have to be a mechanic, anyone who can use a fire extinguisher and telephone will do.

Brake work calls for a few special tools. To loosen the bleeder valves you need a special bent-neck six-point box-end wrench. See the Harbor Freight catalog. They sell assortments of brake tools. I don't know if the assortment they sell is suitable for a Volkswagen but the illustration will give you an idea of what you're looking for.

This whole series of articles is about tools. You can't maintain a vehicle - ANY VEHICLE - without the proper tools. Proper tools are kinda like an IQ test. You can do the job – once – with a hammer or pipe wrench or vise-grips or whatever the instant experts say is kewl but that's it; you've buggered the part. If it survives long enough to need maintenance again you'll find yourself worse off than you were before. The smart way to do it is to buy or make the proper tool.

Early Volkswagens used bleeders with 7mm heads on the rear wheels and 11mm heads on the front. Later models used… whatever the hell it is. Crawl under, find out what size your vehicle requires and procure the proper tools. These become part of your Brake Tool Kit and should reside there, apart from your regular tools.

If any of your bleeder valves have been buggered up or are rusty, clogged or whatever, replace them. Bleeder valves are fall into the category of 'consumables,' items that require periodic replacement. And since bleeder valves are a standard maintenance hardware items, most good auto-parts stores carry them in both metric and SAE flavors. But the secret of consumables, which also includes Zerk fittings, ignition parts, generator brushes and so on, is that you don't buy them as you need them, you buy them BEFORE you need them – you always keep a few on hand, replacing the bad one when you come upon it and using the old one as a memory aid. Lotsa guys just put them in their pocket. Next time they go to the parts place, when the clerk sez 'Will there be anything else?' you dig in your pocket and there, along with your pocketknife, a dirty hanky, a hunk of wire and a piece of string about… that long… will be the bleeder valve.

"Yeah," you say. "Gimme two of these."

To bleed your brakes you'll need a bleeder hose that fits over the bleeder valve. Here again, find the size that fits your vehicle and buy about eighteen inches of it. Common vacuum hose works fine but not for long. Cheap hose is made of natural rubber. Brake fluid eats it up.

To turn a length of vacuum hose into a bleeder hose, find a SHORT screw or bolt that is a force-fit in the hose and use it to block one end. Using a pointed Xacto knife or the corner of a single-edge razor blade, make a penetrating cut in the side of the hose just above the end of the screw or bolt. The slit will act as a flapper valve; you can force brake fluid OUT through the slit but it will not allow anything to come back IN.

The last item you need is a glass jar.

Start with the wheel farthest from the brake pedal and end with the wheel closest to the brake pedal.

To bleed your brakes, fit the wrench to the bleeder valve, slip the open end of the hose over the bleeder valve and put the end of the hose with the screw into the jar. Pour enough brake fluid into the jar to cover the slit then loosen the bleeder valve, go around to the cockpit and pump the brake pedal ten times, refilling the master cylinder as needed.

To CHANGE your brake fluid you simply keep pumping until you know that circuit is charged with fresh fluid.

While the symptom of spongy brakes usually means the system needs to be bled, it can also reflect an incipient failure of a brake hose. To check for this you must visual inspect each hose while someone pumps the brakes. Look for any swelling or unusual motion in the hose. If you've got a bad hose, you'll have to get it out of there. This calls for a couple more wrenches unique to brake work.

Use standard replacement brake hoses rather than those kewl after-market jobbies. The standard hose is good for twenty years service. With the after-market stuff, dirt gets into the exposed metal braid and normal flexing is enough to wear them out in a surprisingly short period of time.

Another no-no is those kewl suction-type bleeders. Avoid them like the plague. Your brake system uses a type of chevron seal. A chevron seal works when the pressure is behind the seal, forcing it tight against the cylinder wall. The more pressure, the better it works. When the pressure is released, the elastomeric seal retracts allowing the piston to slide back into battery. But if you apply SUCTION behind the seal when the piston is already retracted (as is the case when bleeding brakes) air will be pulled past the lip of the seal. You can suck all day and you'll still

see bubbles in the brake fluid… because YOU are sucking air into the system through the wheel cylinder. (The little hand-suction kits are handy for checking the vacuum canister on your distributor, for systems using O-ring seals or for do-it-yourself abortions but they should never be used to bleed the brakes on a Volkswagen.)

Another no-no is those ohsokewl after-market wheels that conceal the brake-adjusting hole on the older style drums. You should adjust your brakes WHEN NEEDED. For younger drivers, that can be once a week. I've seen plenty of bugs in desperate need of a brake adjustment that wasn't done because the owner couldn't remove the over-torqued after- market wheels.

Adjusting your brakes is sooper-simple. But the devil is in the details. For an early bug or bus you need your jack, a flashlight, a medium-size flat-bladed screwdriver and your hubcap puller, if you got pullable hubcaps. Plus you need to know where the adjusters are. Buses are different from sedans and front wheels are different from rears.

If you got something with 4-lug drums, such a 1968 or younger sedan, then you need the floor jack and a pair of jack stands. Why? Because the adjusters are on the back of the wheel. And any time you have to put any part of your body under the overhang of the vehicle when the wheel(s) are not on the ground, you support the vehicle with jack stands. (Macho types always ignore such 'silly' rules. Don't worry about it. It's the type of problem that creates its own solution. Darwin was right, you know :-)

The brake adjusters are sleeves that are threaded on the inside. Turn the adjuster one way, it spreads the shoes apart. Turn them the other, the internal springs pull the shoes closer together. To adjust the brakes you turn the screw until the shoe is touching the brake drum then back it off until the wheel can be easily rotated with no sound of dragging.

The Idiot book offers a good how-to on adjusting your brakes, mit pitchers yet.

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Doing a Brake Job…

…is pretty easy. And since all of the manuals tell you how, I won't. Read the manuals. Study the pictures.

The hard part is removing the rear drums. I've already told you how to do that (see Part One). Whatever you do, don't go banging on things with a hammer. Through a process called 'brinelling' the pounding creates micro-flats on the race & roller (or ball). Once the roller & race are no longer true, the thing wears out quick like a bunny. So don't do it, no matter what you read in Muir and all the magazines. (For the straight dope check the Journal of the Society of Automotive Engineers. The cause of premature roller- and ball-bearing failure was identified in the early 1950's.)

Another thing often overlooked by the novice is the need to LUBRICATE your brakes. Not the shoes but the adjusters and wherever metal parts move against each other. They make special grease just for this purpose.

If your wheel cylinders are leaking they need to be overhauled or replaced. And if you have leaky wheel cylinders, odds are the master cylinder has gone bad too. Why? The slave cylinders go bad because you've allowed water to build up in the fluid. If there's enough water in the system to cause pitting of the slave cylinders you can bet your bippie the same thing has happened to the master cylinder.

Overhauling a brake cylinder means honing out the pits, polishing the bore and replacing the seals. A wheel cylinder kit typically costs only a couple of bucks. But if you've never overhauled a hydraulic cylinder, this isn't the place to start. Buy rebuilt or new replacements and plan to overhaul the old ones.

The best cure for leaky brakes is to not let it happen. You can prevent the rust that causes the pits by replacing the brake fluid every couple of years. Easy.

Often times I find VW slave and master cylinders so badly pitted they can't be honed, they need to be re-bored and sleeved. (Unless you've got a shop full of tools and a lot of spare time, you can't afford that.) When the cylinders are that bad there's a good chance the hydraulic pipes are also rusty. There's no way to heal a rusty brake line. It must be replaced.

Oddly enough, one of the most frequent results of rusty brake lines is conversion to disk brakes, which cures absolutely nothing. The logic here is slightly baroque so follow me through. The rusty brake lines are restricting flow and the vehicle's braking performance is poor. The vehicle has a history of brake problems and no amount of bleeding or cylinder replacement seems to help. For some reason the owner decides the problem is in the brake DRUMS (disks are better, right?) and off he goes on a very expensive trip down the slippery slope.

Volkswagens have pretty good brakes, as numerous tests have shown. Before you decide to 'improve' the braking system, make sure it really needs it.

Another oft-seen error is failure to replace the grease seals on the front wheels when doing a brake job (or even when repacking the front wheel bearings). I had a kid come by the shop after replacing his front shoes twice in six months, wondering what he was doing wrong. His left front brake drum didn't have a grease seal. He was using the Muir manual which mentions the grease seal only in passing, putting no emphasis on the need for periodic replacement. But the 'official' Bentley manual isn't any better. The grease seal isn't even mentioned in the brake section. Under the section for the front end it mentions only 'Seal for disc.' It is illustrated in the exploded view of the drum-type brake but there is no nomenclature associated with it. Haynes also ignores the seals. Which is probably why I see so many bad front brake jobs.

When grease or oil gets on the drum it will contaminate the shoes. Since none of the common sources of information put any emphasis on the need to insure the seal is doing its job it comes as no surprise to find a lot of bad seals out there… and a lot of bad brakes… and a lot of Conventional Wisdom that sez veedubs don't have good brakes. (But buying that expensive disk brake kit will fix EVERYTHING, right? :-)

Front axle grease seals are inexpensive. The old style used a fiber seal; you had to replace it pretty often. Later versions are made of synthetic rubber and last a long time (your wheels don't rotate very fast). But on a rotating shaft even the best seal needs to be replaced now and then.

The oil seals on the rear axle are a different case. Since the rear axle seals remain in place when the wheel is removed they are normally replaced only when you R&R the bearing.

Ready to do a brake job? Then read your manuals. Be sure to arc the shoes and to keep things clean. Ignore the kewl instructions in the Muir manual for burning the oil off a contaminated brake shoe. That's an old Model T Ford trick. It only applies to asbestos linings installed with rivets. Modern brake lining material does not contain asbestos and the lining is bonded to the shoes with special glue that will be destroyed by burning (when bonded brake shoes are overhauled the first step is to bake them at a temperature that causes the glue to breakdown, allowing the old lining to be easily removed).

Brakes are easy. Keep them adjusted and replace the brake fluid every couple of years, you'll always have good brakes.

-Bob Hoover
-16 April 2K
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