Bleeders sucking air?

[jlwdvm]

Is it possible for bleeders to suck air around the threads and then expel it with the brake fluid during bleeding? I have Wilwood 6 and 4 piston calipers with a completely new system on my Firebird. The brakes work good enough to drive the car, but there still doesn't seem to be the level of stopping power I am expecting from the manual system that Ron Sutton put together for me. I have bled several times, but don't know what to expect from pedal feel with the manual system. It doesn't feel like there is obvious air in the system, but the brakes feel vague when stopping (if that makes sense). I decided to gravity bleed last night and started at the passenger rear inside bleeder. I was watching the fluid flow and every once in a while I would get a bunch of bubbles coming out with the fluid.....then it would be back to straight fluid. When the bleeders are loose enough to get flow, they are also loose enough to wiggle. I decided to wipe some grease at the base of the bleeder to help seal it off from the outside. I still would occasionally get bubbles. After extensively bleeding the passenger rear, I moved to the driver's side and seen no bubbles...haven't done the fronts yet. Just wondering if I could have had that much air in the system and still have a fairly decent pedal...or am I sucking air around the threads of the bleeder and then seeing them come out with the fluid?

[dhutton]

I am going to say no. If there is fluid flowing out of the bleeder then there is no pressure differential to suck air in around the threads. I doubt the flow rate is high enough to create a venturi effect. If you are getting fluid for a while followed by bubbles that would say the air was further upstream.

I am not a disc brake guru so take this for what it’s worth....

Don

[jlwdvm]

I got to thinking...if there was leakage around the threads, wouldn't brake fluid be coming out around the threads instead of air getting sucked in and around? I've used a vacuum pump before as well. That will be strong enough to suck air between the tubing and the bleeder nipple, as well as around the threads. I also reverse bled this car after I reinstalled my Wilwood master (after it went back for the recall rebuild).

[dhutton]

I think you have a small leak. Did you use stainless brake lines? I would back off eac fitting a retighten then to reseat the flares.

Again, not a guru but this is what I would do.

Don

[jlwdvm]

I've checked for leaks and have found nothing. I used NiCopper line (the goo stuff imported from England) and an Eastwood flarer. All calibers are now flushed/gravity bled. I thin part of my problem is that the pads-rotors aren't bedded enough yet.

[Chad-1stGen]

I don't think the bleeder threads are where the air is coming from in a gravity bleed. However, I wasn't able to effectively use a vacuum bleeder on my Wilwood calipers until I put some pipe tape on the bleeder threads. Prior to that I was getting some air leaking past the threads and into the bleeding tube.

[GoodysGotaCuda]

I had problems bleeding my Wilwoods and would suck air past the threads when using a mighty vac.

In the end, I found the old fashioned put a hose into a bottle of brake fluid to be the best solution. The resistance of sucking the fluid in/out was less than pulling air past the threads.

Also ensure the calipers/bleeders are vertical. The rear was fine on mine, but the fronts were leaned forward when installed. I took the top bolts out and rocked the caliper so that it was vertical.

You can also try a hose on an inverted bottle with the bottle higher than the reservoir. This would force air/fluid to travel from the inverted bottle [with a air vent] through to the reservoir.

[jlwdvm]

I don't think the bleeder threads are where the air is coming from in a gravity bleed. However, I wasn't able to effectively use a vacuum bleeder on my Wilwood calipers until I put some pipe tape on the bleeder threads. Prior to that I was getting some air leaking past the threads and into the bleeding tube.

I had the same problem when I used my vacuum pump. I used it to get the majority of the air out of the system and I have bled the system with the pump method, and now gravity bleed every so often as I put a few miles on the car here and there. I figured that it would take several attempts over time because every component of the system was new. THe Wilwood bleeders are wiggly loose when they are open far enough to get fluid flow, but I thin the bleeder hole is so far down that it doesn't matter (when external vacuum isn't placed on the system. I just don't know what a manual pedal is supposed to feel like when the car is parked (and I hit the pedal) or moving. To me, it doesn't feel like it has to get pumped up to get pressure. I can still see/feel the machining marks in my rotors, so I think brake grab and feel will get better as the pads and rotors bed in.

[gray86hach]

You need a Motive Products brake bleeder. The time I saved the first time I used it made it worth every penny. Next time I used it on the clutch and it was a 10 min job vs the hour it took doing it manually

Tim

[jlwdvm]

I'm not sure the Motive will do any better at getting all of the little air bubbles out, as opposed to gravity bleeding. It would be faster, but I just made sure that all of the old fluid passed through the system and was replaced with new. The system was initially vacuum bled at each corner.