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  • Writer's pictureRoger Maeda

5 Quick Tips for Better Brake Bleeding

As we all know, bleeding your brakes is an essential skill for any mechanically inclined automotive enthusiast. We also know, brake bleeding can also be an unpleasant and tedious experience, as stuck bleeder screws, brake fluid spills, and persistently soft brake pedals seem to always crop up on the road whenever you attempt to purge the brake system of air.

So here are a few obscure tips from our garage that will make this process a little easier:

1. Loosen Bleeder Screws with Your Ratchet

If you are reading this article, you have probably run into at least one bleeder screw that was stuck, seized, or had been completely rounded off. The reason for this is very simple. Because the tapered inner tip of the bleeder screw needs to seal tightly against the chamfered hole in the caliper, these screws are made of soft, non-hardened steel. This makes all too easy for them to seize in the cast steel caliper as heats, cools, and gets splashed by water during the course of everyday driving.

When it comes time to bleed your brakes, your open wrench just slips off the hexagonal section of the bleeder screw, rounding off the corners and making it impossible to remove. So what can you do to prevent this?

The answer is to use a standard 1/4" or 3/8" ratchet with a tight-fitting 6-point socket to loosen your brake bleeder screws. The larger contact area and shape of your 6-point socket will help keep the hexagonal head of the bleeder screw intact while you apply the torque necessary to break it free of any rust that might be holding it in the caliper. Once you have the bleeder moving freely, you can switch to your combination wrench or flare nut wrench so you can attach your hose and get bleeding.

One word of warning here - Don't tighten your bleeder screw with a ratchet. The recommended torque figures for bleeder screws are between 6 lbs-ft to 10 lbs-ft (8 - 13 N-m). You could generate that much torque through a standard 8" long ratchet if you put two fingers on the handle and gave it a gentle squeeze. If you tightened one of these bleeder screws with the same vigor as you would a regular 10mm hex bolt, you could easily strip the threads or snap the bead clean off of the bleeder.

Instead, use your combination wrench, flare nut wrench, or if you want to be extra careful, a lbs-in torque wrench to tighten the bleeder screw.

2. Keep the Reservoir Cap Loose

This is a tip to prevent accidental spills more than anything else. After all, if the seals in your master cylinder are in good condition, they will have no problem handling the small amount of vacuum that forms in the brake fluid reservoir when you bleed the brakes.

The issue comes when you open the cap to refill the reservoir with fresh fluid. When you loosen the reservoir cap, the air from the surrounding atmosphere rushes in, causing any fluid remaining in the fluid to splash out and covering your fingers and the firewall with brake fluid. Not only is brake fluid bad for your skin, but it also dissolves the paint on your car. So you want to keep the mess contained as much as possible.

All you need to do to prevent this is to open your reservoir cap and keep it loose throughout the entire brake bleeding session. It's just one less mess to clean up.

3. Use a Motorcycle One-Man Bleeder (and a Big Container)

You may have seen our previous article on the best one-man brake bleeders for your money, where we recommended inline one-way valve type one-man bleeders commonly used on motorcycles. The one thing we didn't mention was how much time it saves, specifically because you can use a giant waste bottle for the old brake fluid.

While this might not seem significant, this can be a huge time saver. Your average car's brake system holds anywhere between 32 fl oz to 64 fl oz of fluid (approx. 1L - 2L of fluid). When you bleed all four corners of your car's brake system, you can expect to pump about 16 oz (~470ml) of that fluid out of the bleeders. If your waste bottle is big enough, you don't need to stop partway through bleeding one caliper, which minimizes the chances that you accidentally knock the hose off of the bleeder nipple or spill dirty brake fluid everywhere while transferring it to a bigger bottle.

Even in those rare occasions that I have a second pair of hands to help, I will still opt to use a motorcycle bleeder instead of a length of plain hose. The one-way valve in the bleeder serves a great backup mechanism in case my hand slips and I can't get the bleeder screw closed before my helper finishes depressing the brake pedal. All in all, it's a huge time saver as well as a preventative for frustration.

4. Wrench Open Bottles for a Mess-Free Pour

In stark contrast to its innocuous appearance, brake fluid is horrible stuff. It will irritate your skin, dissolve several kinds of plastic, accelerate corrosion on metal components, and will strip the paint off your car. You don't want it to get anywhere that it shouldn't be.

You can keep the mess contained by opening your new brake fluid bottles in a particular way. After you pull the cap off a fresh bottle of brake fluid, take the open wrench that you use on your brake bleeders, hook the open end on the lip of the bottle, and use it to punch a hole in the seal as if you were using a can opener. Then turn the bottle 180 degrees and punch another hole on the other side.

Now when you pour your new fluid, it will come out in a steady stream instead of glugging and splashing all over your engine bay. Easy.

5. No Bubbles? Keep Bleeding Anyway

Yes, one of the main objectives of bleeding your brakes is to get air bubbles out of the brake system. But don't stop after a few pumps just because you don't see any air bubbles coming out. Most of the bubbles that form in your brake system are microscopic in size and cannot be seen with the naked eye.

Instead, get into the habit of pumping out all of the fluid in the caliper every time you bleed the brakes. That's usually between 5-10 pumps per caliper for standard single or dual piston floating calipers, and more if you have fixed calipers.

While this might feel like a waste a waste of brake fluid, there really is no other way to ensure that you are getting all of the air out of your brake system. Besides, doing a few extra pumps is a lot easier than taking the wheel off and bleeding that corner again.

That's all I have for you today. Pump hard, wear protection, and try not to make a mess.

See you at the track.


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