trouble bleeding brakes on 66 after replacing lines and changing to duel Master cyl

[JrJc66]

I replaced all the brake lines and hoses as well as switched out the single master cylinder to a duel master cylinder. Well I had no trouble bleeding out the rear brakes but the fronts are a different story. Brake peddle will only go half way to the floor even with a front bleeder open. The fluid in the reservoir has not moved at all. What could be causing this? Could the front wheel cylinders be bad? As a quick background, I bought the truck last summer with a broken brake line which is why I decided to do the duel MS swap. I have yet to have the truck on the road. Supposedly all brake parts within the drums are newer. I haven't taken any drums off the verify. Any help or hints would be greatly appreciated. Thanks

[KJSR]

Make your drum brakes are adjusted tight and then try to bleed.

[T and S]

I would definitely remove the drums and do an inspection to make sure every thing is up to snuff. Almost sounds to me like that is where the problem may lie.

[luvbowties]

Originally Posted by JrJc66

I replaced all the brake lines and hoses as well as switched out the single master cylinder to a duel master cylinder. Well I had no trouble bleeding out the rear brakes but the fronts are a different story. Brake peddle will only go half way to the floor even with a front bleeder open. The fluid in the reservoir has not moved at all. What could be causing this? Could the front wheel cylinders be bad? As a quick background, I bought the truck last summer with a broken brake line which is why I decided to do the duel MS swap. I have yet to have the truck on the road. Supposedly all brake parts within the drums are newer. I haven't taken any drums off the verify. Any help or hints would be greatly appreciated. Thanks

What does pedal feel like with all bleeders closed? Do you have brakes on front and rear? Maybe your brakes are okay. Isn't the whole purpose of dual brakes to allow you to have brakes(via at least partial pedal) even if fluid line blows out on one end?--and this scenario is what you are simulating with rears bled and adjusted AND with a front port open.

Try it the other way: when u pump up brakes and hold, how far down does pedal go when a rear port is opened? This, again, simulates a fluid line blown out on one end--but opposite end this time.

EXACTLY what master cylinder did you use?

Also, definitely follow T and S's reply.
Sam

[65CowboyCaddy]

Was master cylinder bench bled? Try jacking the rear end way up in the air, this will place any air in master cylinder to the rear of the master ready to be burp. Take cover off reservoir, press pedal gently several times look for bubbles.