Bleeding Brakes

[demon69 13]

Hi
I have a 69 Mach 1 with front disc and rear drum brakes.  I recently replaced the master cylinder and I am now having trouble bleeding the front brakes, the rear brakes are okay.  As a process of elimination, I blocked of port on the MC going to the proportional valve, firm pedal.  I then reconnected the MC line to the proportional valve then blocked off the lines to the left and right brake callipers.  Again, firm pedal.  But when I re-connect the lines, re-bleed the front brakes, I have very little pedal pressure.  Obviously there is still air in the lines and/or the callipers.  I have bleed the brakes using the conventional method of pumping the brake pedal and opening and closing the bleed nipple in sequence, I have also tried using a vacuum hand bump to draw the fluid through but again no success.  If any one has experienced a similar problem, I would appreciate your advice on rectifying this problem.  It has become very frustrating as I have bled brakes many times before on different vehicles with 100% success.     

Thanks
Peter

[fvike 173]

Did you bleed the MC before installing it? Air might be trapped in it.

 

[demon69 13]

Yes, bench bled MC before installing.  As mentioned, I have good brake pedal up to the proportional valve, after that is the problem.

[Brian Conway 264]

http://1969stang.com/forum/index.php?/topic/54219-bleeding-master-cylinder/

 

Try the search function.  Lots of pertinent info available.  Brian

[machm1970 180]

I had the same problem, I bought a set of the bleeder screws that have the little one way valve in them so you can bleed them by yourself. The pair was like $7. Even after bench bleeding the master I still had air, these worked good and were inexpensive and easy to use. I ran fluid completely through 3 or 4 times before I had a firm pedal. Also, make sure your calipers are on the correct side, the bleeders should face up and back at about 45 degrees, when I bought mine they were facing straight up which is wrong.

 

Matt

[barnett468 418]

Did you post this on the Aussie site also?

 

 

Are your calipers factory?

 

 

If you keep moderate force on the pedal, does it continue to creep down all the way to the floor?

 

If you pump the pedal after it has sat fr a little while, does the pedal stop higher after you push it a few times in a row?

[demon69 13]

Hey Guys

 

Thanks for the feedback, it has been really useful.

 

First point, that link you gave me Brian was really helpful, particularly the image showing the orientation of the calliper and bleed screw.  In my case, the bleed screw is facing up but it is not at the high point of the calliper reservoir.  I have removed the calliper and re-bled the front brakes, there is definite improvement but I will need to go the process again to get a bit less pedal travel.  What is the normal pedal travel you would expect when everything is good?

 

Second point in answer to barnett468, yes, I posted this on the Aussie site as well.  No unfortunately, the front brakes are not factory.  I have attached a couple of images showing the brake pads and the callipers.  Can you tell if the brake pads are the same as factory pads?  Can you identify the supplier of the callipers, I will want to buy pads down the track.

 

[RPM 1,190]

I haven't looked at my stock disc brakes in years, but those sure look like oem 69 calipers to me.

[Rsmach1 71]

By the pic you posted of the caliper looks like that was the problem, it's a fairly common mistake.