Air in brake lines

[Rob Webb]

So I have done a frame off restoration. The last thing to do was bleed the brakes. All new brake lines, new Wilwood Master cylinder, new wilwood front calipers, rebuilt the rear drum with new wheel cylinders.
I bench bled the Master Cylinder, When I installed the Master and have the proportioning valve plugged off I have solid pedal. I have no leaks and I can not stop getting air out of my brake lines. So now I'm splitting off. I have the fronts plugged off and trying to get just the back brakes bled I keep getting air.
I have used a Motive pressure bleeder, A hand pump bleeder from Harbor Freight but still air? Any suggestions? I did not use any Teflon tape? All new hoses, etc
Thanks

[AussieinNC]

Post a pic of the "proportioning valve" please.....

Was this a drum / drum truck to begin with? If it was and you are reusing the original distribution block it will be difficult to get a good pedal.....

There is an electrical switch in the distribution block that is used to identify a brake circuit failure....to bleed the system, remove the switch ! it can lock over and cause all sorts of issues....

Are the rear brake shoes adjusted correctly?

[71cheyennesuperlongb]

I have seen where people have used teflon tape on many systems.Brake systems are not to be used with teflon tape! Tape is to be used on tapered pipe threads only! Not on compression fittings,not on flared brake lines,not on flared fuel lines, just pipe threads.

[RichardJ]

>>Brake systems are not to be used with teflon tape! Tape is to be used on tapered pipe threads only!<<

You are not understanding the use of the Teflon tape. The tape is not used to seal the brake system.

The tape is used to prevent leaks around the threads during the bleeding process. ONLY.

If you use one of the aftermarket self-bleeders with the internal valve, they usually include a tread sealer pre-applied in lieu of a Teflon tape.

The tapered end of the bleeder does all the sealing. Fluid moves past the open taper into the side hole and out through the nipple. A hose from the nipple into a collection bottle will not stop air from entering through the threads when the valve is closed during manual bleeding.

When vacuum bleeding, you can sometimes pull more air past the threads than fluid being pulled past the partially open taper seat. I.E. air enters around the threads, goes into the side hole and out the nipple, into the bleeder suction hose. Always use a collection reservoir so that you are not pulling fluid directly into the hand vacuum pump.

If you are using a Phoenix REVERSE FLOW BLEEDER, you will push more new fluid out past the threads than fluid past the taper seat INTO the system.

[Steeveedee]

I worked on the assembly line at a GM plant for a time and as an ASE-certified, state-licensed brake mechanic for even longer, and never saw Teflon on any brake component. I disagree that Teflon has any use in a braking system. I am retired, still do my own brake work, and usually only gravity bleed the systems I have. I've not had a problem that way, but a bleeder ball would speed up the process.

[RichardJ]

>> I disagree that Teflon has any use in a braking system.<<

I said specifically that Teflon was not used as part of the brake SYSTEM.
I said it was useful as part of the BLEEDING APPARATUS.
Even when gravity bleeding the Teflon could keep any fluid leaking onto the backing plate or caliper.
Some valve threads are looser fitting than others.

[Steeveedee]

Originally Posted by RichardJ

>> I disagree that Teflon has any use in a braking system.<<

I said specifically that Teflon was not used as part of the brake SYSTEM.
I said it was useful as part of the BLEEDING APPARATUS.
Even when gravity bleeding the Teflon could keep any fluid leaking onto the backing plate or caliper.
Some valve threads are looser fitting than others.

Your mileage obviously varies from mine.

[franken]

On a stock dual res. system, the block under the MC has a valve in it that needs to be locked in place when bleeding.
I seem to recall the process is bleed the farthest spot 1st to the closest, so right rear first, left front last.

[HO455]

Welcome Aboard. Did you have to use any reducer adapters on any of the brake lines? If so are they all inverted flare reducers?