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Bleeding Brakes - When do Bubbles Stop?

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I have bled my 2017 GT brakes many times and have never had the bubbles completely stop. I use a home-made pressure bleeder as shown in the attached pictures. I follow the recommended wheel sequence starting with the right-rear. The bubbles never completely stop at the RR. They sometimes stop at the other wheels but not always. I usually just run about 2 liters of new fluid into the system and call it good. I always replace my pads before the friction material is worn 50%. My brake pedal is always solid and I have no brake problems at the track. I'm wondering if someone here can tell me why I can't get all the air out of my brake system.

Bubbles.pngPressure Bleed Cap.pngMy Pressure Bleeder.pngPeanut Butter Jar.pngTwo Liters of RBF600.png
 
That's a lot of bubbles. Looks like somehow you're letting air into the system. Get a helper and try it the old fashioned way and see how that works.
 

racer47

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Take the bleeder out, wrap the threads with 3 or 4 turns of teflon tape, screw it back in finger tight such that the threads seal but the bleeder does not. Then try it. You may be pulling air in through the bleeder threads like azboss said. Clean off all the teflon when you're done.

The hose to bleeder looks tight but you can also put a zip tie on it or safety wire to make sure it is not leaking air.
 
Buy quality 'speed bleeders' and problem solved. As much as I liked my pressure bleeder system, once I put speed bleeders on it made the process much quicker, less messy and no issue with getting air into the system.
 
Thanks, guys. I have always suspected air is somehow entering at the bleed screw but I couldn't see how. I will investigate further after Amazon delivers more fluid tomorrow. The teflon gambit seems promising. As for the helper method, my most willing and able helper is only three years old and she isn't strong enough to overcome the return spring. I will try speed bleeders.
 
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After bleeding all four wheels I returned this morning to the right-rear to see what I could learn. I followed my usual procedure but for the first time found no bubbles. Always before there were no bubbles until ten or twenty seconds after I opened the bleed screw, then bubbles continued until I closed it. Today, I flowed almost a half liter of fluid into my peanut butter jar without seeing any bubbles. So what's going on?

The main difference this time is that this is the first time I have returned to the RR after bleeding the other wheels. I think I have always had air trapped in one or more pockets that contribute bubbles to the RR but flow to the RR can not clear those pockets. If these pockets of trapped air are cleared by bleeding the other three wheels then that would explain what I have seen this morning. Anyhow, that's my guess.
 

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How? Wouldn't that be basically the same as the M/C piston making pressure?

I’m a aircraft tech for a major airline. And when we have to bleed a certain part of the brake system we have to stay under a specific psi. If we use over the psi they say it could cause air in the system. I’ve never used a pressure bleeder on my cars. I do it the old Fashion way. lol
 
The pressures used to bleed brake systems (15-20 psi) are insignificant compared to the pressure in the system during normal operation. Such low pressures can't cause air to go into solution. The only danger I see with too high bleed pressure would be bursting the MC reservoir.

I'm pretty sure my theory above explains my bubbles. I will try to confirm it the next time I bleed my brakes. Thanks everyone, for the comments and suggestions.
 
I can confirm that the GT rear caliper bleeder screws allow air down the threads and back out the hose barbs. In order to get a good bleed, you need to use the 2-person method and just barely open the bleeder screws in order to avoid this. Teflon tape might work, but traditionally teflon sealer compound is used to avoid the unlikely even that a piece of tape comes free and blocks up an orifice somewhere in the system.
 

xr7

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Who makes or sells a quality speed bleeder?
I back the bleeder screws nearly all the way out and coat it with anti-seize compound. This usually keeps air from traveling down the threads, also keeps bleeders working for years.:)
 

ArizonaBOSS

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Not sure if that was a rhetorical question, but the best Speed Bleeders I have seen are the Russell-branded ones. They use an internal check ball instead of a spring-plunger seat that some other brands (Earls, etc.) use. The Russell ones also come with sealant pre-applied to the threads to help prevent at least one of the issues that we are discussing here.
 

xr7

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Thanks for the reply ArizonaBoss, was not a rhetorical question, just looking for a recommendation for what works and what doesn't. As it has been said before this gang of racers saves us less experienced folk from wasting funds on stuff that doesn't work.;)
 

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