Replace your bleeder valves

#1

Bottom line. I just replaced all my bleeder valves. If yours are old, then you should too.

Details.
Years ago I was using “Speedbleeders” brake bleeder valves. They’re pretty cool. They have a checkvalve in them. Turn them a little bit and they turn into a one-way valve. This means you can hook up a hose and jug, jump into the driver’s seat, pump your brake a bit and then just get out and close the brake valve. Don’t need 2 people. Don’t need a pressure jug.

They didn’t last long tho. The first one failed after about 2yrs, and by 4yrs, none of them would do the cool checkvalve thing. So I replaced them with conventional checkvalves.

Tonight, #1 son and I replaced the master cylinder that I’d grown suspicious of at CMP the other weekend. My brake fluid was old so rather then doing my cool MC replacement trick that doesn’t require bleeding the corners, I did all conventionally. Therefore, I had to bleed the corners. And none of the corners cooperated all that well.

In order to get fluid to move I had to loosen the checkvalves so much that they leaked at the threads. And it seemed to require a lot of pressure with the pressure jug to make fluid come out. I think one is only supposed to put 10psi in the jug and I couldn’t get any fluid to come out until it was over 11psi. Remembering how those Speedbleeders failed years ago, I went to the local autoparts store and bought new bleeders.

It only took a moment to install the new bleeders and immediately all 4 corners started behaving. The fluid would come out at a reasonable rate without having to turn the valve so much that it started leaking at the threads.

It’s not clear to me how they quit working. There’s no water in the system to speak of so they can’t rust. There’s no contamination in the fluid to plug them, so the cause of the failures is a bit of a mystery. Generic bleeder valves can be found for just a couple bucks tho, so replacing them is trivial. If you’ve not replaced yours, I would.

#2

Are you gravity bleeding? I have recently replaced my master cylinder, bench bled and then bled the fronts without any issues.

With that said, I think it would be worth wrapping the threads in teflon tape to make them seal. That way you might be able to use the water in a bottle trick to simulate a speed bleeder. (Work related observation.) Haven’t done it yet.

#3

No, not gravity bleeding. I use a jug-type pressure bleeder.

I never really understood the use of bench bleeding. Can you explain?

Teflon tape wouldn’t help. It’s not that the valves leak, it’s that they don’t act as valves. I’m thinking that maybe they get grit inside of the valve mechanism or something. I’m not really clear on just how the valve action works. Why do they flow if turned 1/4 radius? If I had any of those little rubber bleeder valve covers, I’d now use them. I never did in the past. Maybe those rubber valve covers keep bleeder valves working by protecting them from grit.

Later edit. This explains how the valve works. The trick is that the caliper is cleverly designed to allow the little hole in the bleeder to work after 1/4 turn. How does a brake bleeder screw work?

#4

Bench bleeding is to bleed a system before attaching it to the next assembly(in this case it’s the car). Since not much pressures are involved I just run rubber lines from the master outputs(where the hard lines go) to the reservoir. This way you circulate the fluid rather then dumping it. Using a socket, you can activate the master and get all the air out that way. The difficulty comes when you need to reinstall the master cylinder. I like to do it with a partially filled.

The most important observation I have had over the last few years is to never actuate a master cylinder too far. I recently worked on my girlfriends truck and she did press the brake pedal while bleeding all the way in. The master is 15 years old and it certainly doesn’t feel as good as before. It’s noticeable for me, less for her.