Brake problem

My problem is I don't have a good pedal when I first press it, One pump and it's great and and hold pressure after that.

I just recently switched from power to manual brakes, I bench bleed my master cylinder twice as well as the brakes. Because it reminds me of having air in the system.

Right after I got the car I converted the rear to disc, I've always had to pump the pedal at least once to get a good feel with it. I believed it was because I didn't have enough vacuum for the booster, but it's still doing it now.

I didn't install an adjustable porpotioning valve, could that be the issue? The only other thing I'm concidering it being is maybe the rear hose is collapsed? It's the only thing other than steel lines that I haven't replaced on the brake system.

Most OEM rear disc setups I am familiar with (Mustang based) use a self adjusting feature to keep the pads close to the rotors. That feature is accomplished by the parking brake. As the pads wear, or you retract the pistons fully to put in new pads, the pad to rotor spacing increases requiring two, or even more, pumps of the pedal to get a good pedal feel.

What rear calipers are you using? do they have a lever in the caliper body for the parking brake cable)?

My setup is gm based. They are gm calipers. I will have to check for a leveler, I'm not sure

I know the early GM rear calipers had a very similar design. Not sure about today's stuff though.

GM calipers have to have the pads set to the proper clearance, you have to use the parking brake to do so- the initial set should be one with the cables removed, then actuate the lever until the pads are tight. The reman calipers on the market are often bad. The rear axle bearings have to be switched to green type bearings and the spacer need to be removed from your differential. HTH, Steve

One thing Skeptic kinda touched on that needs remembering

You have to use the parking brake.

Regularly, get in the habit of setting each time you park.

If you do not have that feature working, make it work.

Otherwise you will be back there manually adjusting the brakes, alot.

Plus it helps keep the caliper piston from seizing.

Well I never use my e brake since it's an auto, I never gave that a thought. I will check into it, hopefully that's my problem.

GM rear calipers are very hard to bleed if not removed and re-positioned during the process.

https://www.youtube.com/watch?v=q4_17Gg7tdg

as calipers that have an e-brake mechanism built in must be used to stay adjusted, the setups using an internal drum style e-brake act like a typical drum brake e-brake. you don't need to use it if you don't feel like it. correct ? therefore, if you need a pump or more, i would look closely at your bleeder to make sure it is at the top of the setup when bleeding, even if it requires unbolting the caliper from the bracket to do so.

Seen it more than once where the caliper's were switch side to side on installation, putting the bleeder below the caliper reservoir. Don't think using or not using the E brake ( if your calipers are so equipped ) will solve e your problem.

One has to assume a certain level of competency here. If one put a disc brake kit on and installed the caliper with the bleeders on the bottom, well then that person should quit working on vehicles and take up something that will not potentially harm others due to their incompetence.

Now I can understand an initial mistake resolved after the first drive, but this doesn't sound like that.

Not calling anyone incompetent. Simple check for the OP is all. Don't assume anything has been my experience over the years.

I suppose that is true enough.

This is just a basic encouragement not to get frustrated... just be slow and methodical.

In all the hours and hours I've sent chasing soft brake pedal and uneven brake pad wear problems on my OEM Plymouth brakes, and sharing photos and symptoms here on the forum, the problems have always been resolved - and they have never been more complicated than the following two things:

- Proper bleeding of the components (MC, lines, calipers/cylinders).
- Proper brake shoe/pad advance mechanisms.

It's uncanny how many times I went over and over and over the same setup, saw no problems, but eventually get it to work right by repeating or scrutinizing with absolute certainty the above two issues.

Just my DAMHIK comment.
- Art

To check for air, I would do this:

Engine off, car in park. Pump the pedal a few times to release brake vacuum. This should also push the pads out to the rotors taking up any slop. Unless your calipers have a return spring, the pads will stay right there. Your brake pedal should be rock hard now. If it's still spongy, then start looking for the air in your system.

Thanks for all the help guys. I had a bad master cylinder. I swapped it out for another to try and it solved the problem. Don't know if it was faulty or maybe I bleed it wrong, anyway it's fixed now.