Solving Brake Problems
Replacing your front brakes is not that difficult. However, there are a few key things to remember if you’re going to service them yourself.
One of the main mistakes I see people making when servicing disc brakes is not opening the bleeder valve when compressing the caliper piston. If you don’t open the bleeder valve when compressing the caliper piston, you can actually damage your master cylinder. This won’t happen all the time, but it only takes once to ruin your day. The master cylinder is designed to move brake fluid in one direction. Sometimes when you force brake fluid in the opposite direction through the master cylinder, you ruin its seals and cause it to fail. I’ve seen more than one occasion where someone did this, only to find they have no brakes or a very spongy brake pedal after replacing their brake pads. The fix is to replace the master cylinder.
To avoid all this, open the bleeder valve when compressing the caliper piston. It really doesn’t take that much effort and it potentially saves you the expense of having to replace your master cylinder in addition to the brake pads.
Another common mistake I see is improper lubrication on the caliper slide pins. These are the pins that the caliper slides on when active. These pins are found on many brake calipers (but not all brake calipers).
The proper lubricant is silicone paste, not grease. Grease is petroleum-based and will eat away at the rubber boots on the slide pins. Once the rubber deteriorates it can cause the pins to bind and not move correctly. In addition to that, when the grease mixes with the silicone that should already be lubricating the slide pin, bad things happen chemically. In addition to all that, grease was never designed for the heat that your brakes produce, so it tends to dry up. After it dries up, the caliper slides don’t work and your brakes don’t work as well as they could.
In addition to grease, DO NOT USE ANTI-SIEZE to lubricate caliper slide pins. It’s probably the worst thing to use on caliper slides, because it dries up and causes the pins to seize. I know that sounds ironic considering the lubricant’s name, but it’s true. If you do have anti-seize on your caliper slides or any other lubricant that shouldn’t be there, clean the pins, the bores, and the inside of the dust boots thoroughly before using the proper lubricant. Failing to do so can cause issues with the lubricants mixing. Bad things can happen when you mix lubricants, so do your best to avoid it.
I get asked about other lubricants all the time, but I stick by my recommendation of 3M Silicone Paste. You can use other lubricants designed to lubricate caliper slide pins, but I recommend the ones that are silicone-based or synthetic, not the ones that are petroleum based. Here is a link to the silicone paste that I use.
That covers the main points about servicing front brakes. For more details on how I perform a disc brake service, watch this video.
Rear disc brakes are similar to front disc brakes with one big exception. Rear disc brakes might house the mechanism for the parking brake. You can differentiate between the two types by inspecting the style of caliper piston it contains. If it’s a hollow piston like a front caliper has, then it’s likely that the parking brake mechanism is inside the hat of the rotor, separate from the caliper. If it’s a solid piston with perhaps some grooves machined or cast into it, then your caliper likely has the parking brake assembly contained within it. You can also spot this type of caliper by looking for a parking brake cable attached to it.
If you see either of these things, you handle compressing the piston to accept the new pads a little differently. You can often use a special tool or equivalent to twist the piston back into its bore. Some calipers have access to a screw that needs to be turned in order to retract the caliper piston (some Mazdas come to mind). Check the service manual for your vehicle to see if that’s the case with your vehicle. I still recommend opening the bleeder valve when compressing these pistons to avoid damage to the master cylinder. Here’s a video on the process.
I made a video about this that I’ll post at the end of this section. Most times, you can spot a bad caliper simply by looking at the brake pad wear. If the brakes on the left side of your vehicle are worn to the metal and the other side’s still got 90% of its friction material left, then you likely have a brake caliper issue. It could also be a brake hose or master cylinder issue, but a brake caliper issue is more likely. It could be either caliper that’s bad. Some common issues around this:
- Sometimes calipers won’t release; this causes the brake pads to wear prematurely.
- Sometimes the piston freezes in the bore and won’t apply the brakes, which leaves a lot of friction material because the brakes are never applied.
- Sometimes it’s not the caliper piston that’s at fault; sometimes the caliper slide pins stick and cause the problem. I would suggest you check for this first before condemning the caliper.
Remember what I said about using the proper lubricant on caliper slide pins in the above section? The true test is when I try and compress the caliper piston. If I have the bleeder valve open and I can’t compress the caliper piston, I replace the caliper. Here’s that video I talked about.