- Jul 5, 2006
Autoblog Maintenance 201: Brake pad replacement, Part I
While many aspects of maintenance can be put off until the odometer rolls past 100K, odds are that you'll be doing some work on your vehicle's brakes long before then. Vehicles continue to get heavier and our highway speeds are ever-increasing, both of which put an incredible amount of strain on even a modern braking system. Pads and rotors will wear, and the brake fluid will become contaminated with moisture. If you're lucky enough to live in the Midwest, you can also look forward to the effects of corrosion on braking components. The braking system should be inspected every time the tires are rotated, and one can expect to go through the front brakes every 20-40,000 miles, depending on the vehicle and its usage (rear brakes often go much longer, due to their lesser role).
We'll walk through the process of servicing the disk brakes on a friend's 2000-ish VW Jetta. This vehicle was in need of new pads, and the owner decided that he also wanted to install new rotors rather than deal with the hassle of turning the ones currently on the vehicle, as the vehicle had been sitting for over a year.
Like the other tasks that we've covered in our Autoblog Maintenance series, this is a job that most reasonably competent DIYers can perform at home. While this is relatively simple work, it's a bit more safety-intensive than others in the series. There's the obvious aspect of working on a system responsible for controlling the vehicle's speed, so attention to detail is important. We'll also be lifting the vehicle off the ground, and it's critical to do so in a safe manner. Brake dust can also be hazardous to one's lungs, and even though asbestos has been phased out for the most part, inhaling fine dust particles is never a good idea. We'll also be using some solvents that should not be inhaled or absorbed through the skin. Finally, it's important to protect one's eyes when working with chemicals or flying mechanical bits.
After acquiring and learning how to use the appropriate safety gear, the next step is to select the proper components. OEM parts from your local dealer can be expensive, but they're a safe and reliable choice. If venturing into the aftermarket, consult your favorite online resource to learn what parts other owners have used with success, and which ones to avoid. You'll want to pick up some other materials such as anti-seize, high-temperature brake grease, thread locker, brake fluid, several cans of brake cleaner, and an ample supply of clean shop rags. Most importantly of all, we recommend having access to a factory service manual for the vehicle that you're servicing.
Once we've acquired all the necessary materials, it's time to lift the vehicle into the air, secure it on jackstands, and remove the wheels.
We'll start at the front. Here we have the advantage of being able to turn the steering wheel to gain better access to the brake assembly, so we'll do so. Before going any further, it's wise to make an attempt at breaking free the caliper's bleeder screw, as doing so will be easier with everything still secured to the vehicle. If the bleeder cannot be opened with the proper tools, it will be necessary to remove it using an extractor or via drilling. Often, it's easier and economical to simply obtain a remanufactured caliper.
Next, we remove the caliper slide pins, using a wrench of the appropriate size. This hardware may require quite some force to remove. If it's frozen in place or if the head becomes stripped out, the entire caliper and bracket assembly will need to be removed for the use of more persuasive measures.
With the slide pins removed, the caliper can usually be slid from its bracket; however, in this case, spring clips need to be removed before the caliper could be freed.
With the caliper tied up and out of the way for a moment (nylon "zip ties" work well for this, as do metal coat hangers), remove the hardware securing the caliper bracket to the spindle. Since these are usually quite tight and secured with a combination of thread locker and corrosion, the use of a long "breaker bar" is usually necessary.
After the caliper bracket is removed, the rotor can be slid off the hub and set aside or dumped into the recycling pile. Some rotors, such as this one, will be held in place with a small screw or two; the removal of these fasteners may require a hand-held impact driver. A few whacks with a soft-faced deadblow hammer may ultimately be required to break the rotor free from the hub.
Since the caliper piston will have extended to compensate for pad wear, we will need to force it to retract. Front calipers can usually be pushed straight back with the appropriate tool or a common C-clamp (rear calipers are a different story, as we'll show in a future installment).
The fluid that is present in the caliper may be contaminated, and if this were to be pushed upstream into the ABS module, significant damage could result. Therefore, it's best to open up the bleeder and allow the excess fluid to exit the system. Some even advocate clamping the brake line to keep fluid from traveling upstream, but crushing a brake line - intentionally or otherwise - makes us extremely uncomfortable.
The hub surface is prepped by removing any loose rust particles with a wire brush, and then applying a light coat of anti-seize compound. Also a good idea at this time is to clean the ABS reluctor ring and sensor of any contamination.
After giving it a quick wipe-down with a clean rag and brake cleaner (we'll come back for a more thorough cleaning later), the rotor is slipped over the hub and secured with any necessary hardware.
Before installing the caliper bracket, we'll want to clean the surfaces that contact the caliper to ensure that the two parts can slide freely relative to one another. We're showing it being done here after the bracket was installed, since someone got ahead of himself in the process.
Clean the caliper bracket bolts, and apply a removable thread locker such as Loctite 242.
Install the bracket and its bolts, which are tightened to the manufacturer's spec or until you're sure they won't fall out. The short length of these bolts makes it essential that they are properly tightened, or else they will be prone to backing out and causing all sorts of problems.
Now, we clean the rotors again. It's absolutely essential to leave no trace of oil, grease, or other contamination on the rotor, or else the pads will be ruined, and the brake function may be impaired (lubricants turn to tar under the heat of braking, and wheel lock-up is usually the result).
Being careful of the freshly-cleaned rotor, the slide surfaces of the bracket and caliper are lubricated. Some will choice to use sticky high-viscosity grease, while we've had good luck with anti-seize. Regardless of what's used, it needs to be resistant to being washed away by environmental effects.
The outside pad is now slipped into place, after first being cleaned with a liberal application of brake cleaner.
We install the inside pad into the caliper, and drop the assembly into place.
Lubricant is applied to the caliper slider pins...
... And they are torqued to specification.
That concludes the task of installing new front pads and rotors. The next time around, we'll hit the rear axle, and then go through the process of bleeding the brakes.