Air in brakes. Help

[Kup98ss]

Changed the calipers and hoses in my dad's 69 GTO. Now we get air on both sides. We are on our 3rd mastercylinder and that is not the prblem. Brake hoses are all tight and good. What else could it be?

Thanks for any help.
I know it's not a ls1 but brakes are brakes.

[2001NBMZ28]

You're bleeding them RR, LR, RF, LF right? If so, has to be a leak somewhere, maybe the portioning valve.

[Kup98ss]

You're bleeding them RR, LR, RF, LF right? If so, has to be a leak somewhere, maybe the portioning valve.

Just got back in and that is the conclusion we came up with. Sounds like you know your stuff.
Thanks

[Too Fast]

Are you sure you have the calipers on the correct side? Some cars you can put the L on the R side, and there is only a very minor difference on where the bleeder valve is. If it is not at the very top, then you will have trapped air. If you had no problems before the caliper swap, and did not let the master cylinder run out of fluid during the swap, then you air should be limited to the fronts only. But now since you've changed the master cylinder a few times, you may have air who knows where. Are you bench bleeding the new master cylinder before the install? If not, that will push air through the whole system, and you must bleed as noted above, with the farthest away from the master cylinder first. Myabe you should start by removing the master cylinder, then bench bleed it, then the rest of the system. Good luck!

I've been working on brakes since I was 17, any more questions I'll try to help you! I do this for a living....

[Kup98ss]

We blead it on the bench. That's a work out. We have done it all correctly we are picking up air somewhere.
Proportioning valve is what we are thinking.

Thanks for the help Too Fast.

[rsg98Z28]

had a similar problem on my dads 69 vette, it turned out to be the right rear spindle was bent took quite a few master cylinders and calipers to figure it out.

[Too Fast]

So, the brake pedal was fine before you did anything? It was just a normal worn out repair? Or was it a sinking pedal, with no fluid loss. (that almost always indicates the master cyl. is internally bypassing.

If you are getting air in it, it has to also have a leak, in my experience. When bleeding the brakes, you are closing the bleeder valve before the person in the car is letting the pedal back up, right? Not trying to say you're a dumbass, but I don't know your experience level. (and if you aren't doing it right, you are ignorant, not a dumbass! You just haven't learned yet)

[blue02Z]

how do you know you have air in the system? if there is a leak, it will be letting fluid out as well.

[Kup98ss]

how do you know you have air in the system? if there is a leak, it will be letting fluid out as well.

Air comes out with the fluid. You just want fluid coming out.

[blue02Z]

how extensive have you bled them? sounds like you just need to run like a quart or 2 thru it