2HD's2vettes

Just updated my 79 with a bunch of suspension stuff. All new bushings, control arms coil springs, shocks, etc.

Replaced all new calipers, rotors, bearings, etc. I cannot get the brakes to bleed without visible bubbles no matter what. New master cylinder that I bench bled before install, original steel brake line set, but new flexible lines. triple checked all brake line connections. Using a vac/pump with cylinder can collector for filling and bleeding. Have pulled a great deal of fluid from the master cylinder as far as quantity (no leaks shown) but I can't get a solid flow without air bubbles no matter what. Bubbles are a very consistent patter as seen in the pic below. Calipers were new and bone try after install. Any help greatly appreciated, this is driving me nuts.

** I started on the front, as the brakes are independent F&R and the wheels are presently off the fronts. All other bleeder valves are closed on all other wheels except the one being bled, having the same issues on both sides.

DUB

If you loosen the bleeder too much at the caliper....it WILL allow air to be pulled in past the threads of the bleeder and make you 'think' that you still have air in the system....ESPECIALLY when the air bubbles are a very consistent pattern. Wiggle the bleeder up and down when bleeding and see if the bubble pattern changes. IF SO...tighten the bleeder and back it out no more than a half a turn.

ALSO...I have seen the clear hose that I use...much like what you are doing to direct the fluid into a bucket...actually allowing air to seep past it due to not being totally sealed on the end of the bleeder.

DUB

2HD's2vettes

Got ya, thanks - I understand on the valve (they are new) I have the valve at no more than a 1/2 turn, a little less actually and with Teflon tape. I guess anything is possible on the hose, but it sure seems firm.

redvetracr

"what am I doing wrong??"
for one thing you are using teflon tape, the threads do not make the seal, the bleeder screw and the seat at the bottom of the hole make the seal

tonak

I have a terrible time finding hose that actually seals when bleeding brakes.

jyounane

Two things to consider...

1) I smear brake (rubber) grease around the bleeder threads at the caliper to prevent air getting past the threads. Use plenty of it. Easy to clean up later.

2) It is very important to use very little vacuum when vacuum bleeding. Too much vacuum and you'll pull air past the piston lip seals. Just use enough vacuum to start and maintain the slightest flow.


Joe

2HD's2vettes

I understand that the bleeder screw when seated completely is what makes the full seal, however, when bleeding only, it cannot be seated or it would never pull anything. Wouldn't the Teflon tape help for that bleeding time only? The threads are making the seal for that short bleeding time only - correct?

REELAV8R

If you close the bleeder, apply the brakes do you get a firm pedal. If yes you're done.
x 2

TX-Techman

I can tell you bleeding the brakes on my 69 was no fun at all. I was beginning to think I had master cylinder issues but discovered it was a lesson in patience. If the 79 is like my 69 you are not bleeding in the correct order and may need to bench bleed the master cylinder. Also I raised the front of mine to allow more gravity to help for the rears.

Here is a link to another thread that covers the bleeding order, good luck.

https://www.corvetteforum.com/forums...post1573236348

doorgunner

If it's driving you insane......you are doing it the right way! It took me two days to bleed my manual brakes!

Members say that the Motive bleeder works on Corvette brakes.

mikep3

http://www.motiveproducts.com/
To bleed corvette brakes it's gravity or Motive unit.

You can buy them any where, summit AutoZone blabla blabla.
Maybe a car club in your area has one to loan?

You can Google it and see videos on how it works and where to buy.

Doug Kraft

Maybe you should start with the caliper that is furthest from the master cyl. It will still be a pain but thats how I learned and read it should be done. Good luck and have fun.

TX-Techman

To hell with a manual vacuum pump regardless of brand. I used my HVAC vacuum pump and it was still a test of patience and endurance. Gravity is a huge benefit, brake the line loose at the calipers one at a time a let the fluid flow to that point then reassemble and see if that helps.

For sure you need to start at the the caliper furthest from the master cylinder as stated in the link I posted.

Patro46

Did you bleed the master cylinder first? If not....

This said, I monkeyed with my 74, starting with the furthest away from the master cylinder and worked my way forward. After all, I've done that 100's of times in the past on about every car under the sun. Until now. Usher in my 74 Stingray with all new brake junk. When two days of jacking around trying to bleed them left me feeling spongy

When that didn't work, I ended up using a pressure pot. Took about 10 minutes to do all 4, and worked like a champ. In other words, conventional bleeding methods didn't work in a logically proven manner for me either

DUB

Doing this for a living....I do not have time to gravity bleed...even though it works in some cases...or use a person and do it the '2-person pump the pedal method' I use a diaphragm type pressure bleeder...and nothing but it. It forces fluid through the system under pressure...thus pushing the air out. I have been doing it this way for well over 20+ years and it makes bleeding brakes a 'no-brainer'.

DUB

kanvasman

Following up on the pressure bleeder, do you still need to bench bleed the master cylinder?

TX-Techman

Yes, that is the first step according the the manual.

kanvasman

I wasn't sure since the pressure bleeder works different than the MOTIVE type suction bleeder.

C3Hawk

2 quick thoughts:
1. Totally agree vacuum bleeding can be tricky if more than just a smidge of vacuum used.
2. Gentle taps with a rubber mallet?

Racingswh

So I always use another human. Since it's my Wife's she always helps.

Here's a wrinkle. Friend had a pin hole in a hard line that had worn through from moving slightly against a hard surface for years at the track. No matter how many times he bled he couldn't get the air out. Could almost get a hard pedal but not quite. He finally found it. Took awhile and replaced everything including the ABS pump before checking the hard lines. Lesson learned. Don't rule out anything.