Brake system

[mattmro444]

HAVING PROBLEM WITH FRONT DISC PADS NOT RETRACTING FROM DISC. HAVE REPLACED ROTORS, CALIPERS, MASTER CYLINDER. ALSO NOTICE FLUID LEAKING FROM FRONT TO REAR RESERVOIR ON MASTER CYLINDER. INTERESTED IN ANY SUGGESTIONS.

MRO Supply

[KTL]

Try replacing the flex hose. An old hose will swell and not allow the pistons to retract. Recently saw this first hand on a friend's 1998 F-150 truck.

[Andrea Bichael]

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.
That covers the main points about servicing front brakes. Watch the video for more details Front Disc Brakes and How to Replace Them - EricTheCarGuy - YouTube

[Lapkritis]

Excellent reply Andrea.

I would start in this situation bleeding the system. Any air trapped can expand when heated and cause a hot sticking brake condition. Power bleeding recommended.

[Flat6pac]

Before I spent money in quantity I would change the hose and slip some ZEP 45 under the rubber seals and exercise the calipers. I have also seen the hoses go bad on the 911 and not release the brake.
Bruce

[KTL]

Agreed the master cylinder's primary function is to provide pressure in the compression direction of travel. But people have been retracting caliper pistons for decades w/out destroying master cylinders. I'm not saying that opening the bleeder is not good practice, because it is. Especially when you consider that opening the bleeder expels the most contaminated fluid. But not opening the bleeders is not a guarantee for a failed master cylinder. Brake pads themselves force fluid back to the master during basic vehicle operation.

The commentary on the slide pins is spot-on but not applicable in this instance. The calipers in question are fixed calipers. They're not the abominations of brake design that are the awful sliding calipers that have become common usage throughout the auto industry. What a horse#$%@ collection of garbage those calipers are. Operation typically is imbalanced (inner pad often wears FAR more than the outer) and pads typically fit horribly into the "saddle." I curse them every time I have to work on them.

[brighton911]

Second or third? on replacing the flex hoses. I have too been a victim of a slow release caliper as a result of a tired hose. And for the cost, you also get peace of mind that you won't have to worry about them for a while.