How to Compress Brake Calipers

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Part of the video series: How to Install Car Brakes

Summary: Need to repair car brakes? Learn how to compress brake calipers with expert auto maintenance tips in this free car repair video clip.

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By Nathan McCoullough
eHow Presenter

Nathan McCullough graduated from Nashville Auto-Diesel College with a Grade Point Average of 3.5 and received their craftsmanship award and honor seal. Nathan worked at varies...read more

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hyuri1 said

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on 9/11/2008 Probably would have been good to mention that scraping and prying against the friction surface of the rotor is BAD unless you're planning to replace or resurface them. Another option that usually works (with a single-piston caliper) is to place the screwdriver/prybar between the caliper and the outboard pad, pry just enough to slip the caliper loose, and then compress the piston with a C-clamp. Frequently this can even be done by main force.

Likewise, you should have mentioned that glycol brake fluid (DOT 3/4/5.1) will damage paint, causing it to peel, and that it can be neutralized with plain water. I always keep a wet rag nearby for just that reason when I'm doing brakes, even in the shop. I also use a cheap turkey baster to remove some fluid from the reservoir prior to any work which may raise the fluid level, such as brake service.

Video Transcript

"In this clip we are going to talk about the proper way to compress the brake caliper system. As your pads wear out, the piston actually self-adjusts, it sticks our farther, farther and farther to compensate for the reduction and friction material as they wear. My favorite tool for compressing a caliper is just basically a small flat screwdriver. You never want to pry directly on the caliper piston. That is this component here. It will be round. Where you want to pry is between the brake pad and the rotor or what is left of the brake pad, right in this area. So work your screwdriver in, just like so. Once you've got a decent bite on it, just smooth easy leverage. You can see as the piston retracts the rotor is getting loose. If you don;t compress the piston, it will fit thick new pads inside the assembly. Nice easy smooth motion and you will be able to feel when it bottoms out; that's bottomed out right there. That is how much brake pad is actually missed from the equation. It is not uncommon when you compress the caliper piston see a small amount of brake fluid actually overflow from the reservoir. As they wear, your brake fluid level will drop. That may trigger the brake fluid level switch and turn your red brake light on. If that happens, most people just add fluid to the system. As long as it is not leaking, it always has enough fluid that it will require. So somebody adds it to it and you compress the caliper, it is going to spit out of the top reservoir. So it is not a bad problem to see that. Just be aware, maybe put a piece of cardboard down if you have a nice driveway that you are working in."