My brake peddle seems soft

[crow]

When I pull up to a light and I brake, after a while my car starts to creep. I then notice that I have to press the brake harder in order to stop. On a lenghty light I have to do it several times because it starts creeping again. Last week I installed a new master cylinder and booster. Today I bled the brakes again and stilll it creeps. It seems that if I pump the brakes to a stop they will hold. The brake shoes, pads, rotors and drums are not new but they have lots of miles left on them. None of the brake lines leak. Any ideas why?
BTW, I not longer have the power booster brake system on my 87 GN.
Thanks in advance

 

[Nick Micale]

My first "guess" would be you have air in the master cylinder?

It is also possible your rubber brake hoses are swelling?

 

[Dynalow00]

Are you losing fluid somewhere? (Does the level go down after driving a while?) I am assuming this is a vacuum system since you no longer have the Powermaster system...

 

[crow]

You may have something there. After all, the brake lines are original.
This may sound stupid but how can I tell? Jack up the car and have someone apply the brakes while I inpect the lines? Yesterday I bled the lines and added more fluid. Wouldn't I have noticed then? I assume the lines get obviously bloated when they swell.
It is now a vacum system. Never been really happy with it. The original powermaster was awesome, while it worked.
Thanks for the reply.

 

[crow]

Dynalow00,
The level does not go down that I can tell. Yes this is a vacum syste. Not more than a month ago I took the wheels off to check pads and shoes. No leaks there. The fluid in the system is clear as glass. My wife looked at my newlly installed 3.5" DP and pointed ouit I was out of brake fluid. I told her to look again, hhh! She is a sweetie.
Nick may have something there. I will check that out first. Gotta be able to stopem before you can runem. .
Thanks for your interest and reply

 

[1quick6]

Did you bench bleed the new master cylinder? That's a very important part of getting a good pedal.

I'd have to agree that it sounds like the lines are ballooning. Sometimes you can see it happen while the brakes are applied and in severe cases, the hose will be disfigured.

 

[Red Regal T]

Usually if you have air in the system, the peddle will pump up to a higher level than the first pump. If your hoses look old at all, I'd go for a set of the Russel braided lines. I got a set through Amazon for only $65. Do it! This will improve your braking. If you have all the air out of your lines, I think the problem you are having is that your pads are junk. Invest in some Hawk pads or some other hi-performance pads. Hi-po pads make all the difference in the world.

 

[Red Regal T]

Did you bench bleed the new master cylinder? That's a very important part of getting a good pedal.

I'd have to agree that it sounds like the lines are ballooning. Sometimes you can see it happen while the brakes are applied and in severe cases, the hose will be disfigured.

That is ugly!

 

[crow]

You guys are awesome. I am taking notes and will trace your input down. Have not been able to do anything else because I have been called back to work to cover for a sick coworker on another shift Hopefully he will be returning to work tomorrow. That will give me two days before I start my reg shift.
1quick6, As to bench bleeding the master cylinder, it was not done. BTW, that is ugly. I'd have noticed anything like that while under the car. But who knowws? When fluid is purting out, making a mess, might not have noticed. Will look again.
Red Regal T, I'm not sure if the pedal stoped higher. Today, I pump the pedal while making several stops and noticed the pedal did not bleed down. The pads are old and nthe shoes too but I was assured by a mechanic I trust that they have many miles left in them. Besides, don't screetch, by design, when they absolutely need changing?
Thanks everyone and kedep the ideas coming. I will trace them down till I find the cure.

 

[Red Regal T]

Yes, they probably have a lot of meat on them, but that doesn't mean they're any good. Recently, I installed LS1 discs brakes on my GN. They are dual piston calipers and use a 12" rotor. I bought new pads from autozone for $45. After having done the front only, before going on to do the rears, on test drive, and for a month afterwards, my brakes were worse than my original GN, which were good. The problem was the shoes. I replaced them with Hawk HPS shoes and my brakes are noticebly better than they ever were. All shoes are not the same. Yours are used and of dubious quality and though they have a lot left on them, apparently, they're junk. If you don't want good brakes, stick with them. And don't forget the braided lines.

 

[1quick6]

As to bench bleeding the master cylinder, it was not done. BTW, that is ugly. I'd have noticed anything like that while under the car. But who knowws? When fluid is purting out, making a mess, might not have noticed. Will look again.

You should definitely bench bleed a new master. If you click on the hydroboost conversion in my signature, there is a little tutorial on doing that. I did mine on the car, but most go it on a bench vise.

That's why John mentions braided lines. You won't get swelling with those. Your rubber ones (might be really elastic) could be ballooning and returning to normal size so nothing would really be evident.

 

[crow]

Red Regal 1, Monday I will have the car checked over, the entire brake system, by someone very knowledgeable. Lets see what he comes up with. I'm not opposed to getting new pads or shoes or hoses. Not into taking risks. Been there done that during the VN war.
Thanks for the recomendations.

 

[crow]

1quick6, ran into a guy today with 1qwick6 tags on his car, hhh! Like I posted to pacecarta, I'm not opposed the changing lines. You are perfectly correct, having been a helicopter mechanic in the Army, I'm well aquainted with braided lines. Monday I will know more.
Thanks a bunch for the assistance.