New brakes - spongy or excess travel???

[RAM]

Hello all!!! Before I start I just wanted to say that this forum is the best thing ever!!! So much information that allows you to avoid the BS from local dealership mechanics that think that they can do no wrong. Thanks!!!

Anywho....I just replaced the brake system on my 75 and I still feel the pedal to be spongy. The question is, is it spongy or is it excess travel?

Here's what I did. I replaced the MC, added SS brake lines, rebuilt the calipers, replaced the rubber lines from the reservoir to the MC feed lines and obviously replaced the brake fluid with ATE Dot 4, blue fluid.

I have bled the lines three times, once alone with and EZ bleeder and twice with a helper. Between the last two bleed sessions I removed the excess gap between the pads and the rotors as instructed by "Early_S_Man" in a post dated 8-19-2001.

All this and I still feel that the pedal is spongy. It travels about 1.5" before I get a hard pedal.

So the question is, what am I feeling here? Is it a spongy pedal? Is it excess travel? Or is it that the pads need to be broken in? What else can I do to get a harder pedal?

Any help would be great.

[cstreit]

1.5" doesn't seem like too much, but you can make adjustments to the travel if you like.

Do any wheels lock up first? Car pull upon braking? Maybe STILL some air in the lines...

How does the pedal feel after the 1.5 inches? DOes it get progressively, or very quickly firm? If the latter, it's probably just an adjustment required from M/C replacement. The former points to more air in the lines.

Did you bleed the master cyl? If not, there could be air trapped in there.

[RAM]

The car doesn't pull to any one side when braking and there is no locking at any point. The pedal is firm very quick after passing the ~1.5" mark. I did adjust the pedal travel to the MC and it seems that there is about 1 mm until the pedal hits some resistance. I did not bleed the MC before I installed.

That being said, are there other adjustments that can be made to the MC? Did I do it right the first time. If there is air trapped in the MC how can I insure that I got it all out?

Thanks for the quick response.

Ruben

[KTL]

RAM,

You say you didn't bench bleed the MC, but I don't think that's necessarily a problem. I think when you force bleed (either vaccuum or pressure) the system, bench bleeding is not necessary? I could be mistaken. But, I did not bench bleed my new MC and things worked out fine using the Motive pressure bleeder. Good product by the way.

I tend to think you're problem is that you still don't have the pads in close enough contact with the rotors. I know you said you did this, but it's possible that they're still too far away and that's where you're getting the low pedal. You really have to get the pistons set such that you must muscle the pads in there. When you rebuild the calipers or new calipers with nice new seals in there, this is what happens. It took me a little while to get all those pistons out far enough to close up the gap. Once I got them all cozy with the rotor, low pedal and fear of sponginess went away.

Edit: bench bleeding comments.

[surflvr911sc]

I just freshened up my brake system, new lines, rebuilt calipers, and flush. I had the same problem. I would hit the brakes, the peddle would go almost to the floor, I’d hit them again and the would be rock solid.

Paul (psb911) had the same problem. I called him and he told me that he found out this is “normal” after caliper rebuilds. The outer seals are very tight when new and they retract the pistons back too far. They brake in after a few heat cycles. Mine have done just that. They aren’t 100% yet b/c I haven't put that many miles on the car but every time I drive it they get better. Good Luck.

[Paco Anton]

Ruben,

Can't help with the brakes. I did my first bake bleeding last saturday and still do not feel too comfortable with my mechanical skills.

However, I must say that I like your Avatar.

Saludos,

[RAM]

I think what I'll do is try to get the gap out of the pads again and just use as is for a couple of heat cycles and see what that does. I might even pressure bleed the system (home made or purchased) to see what that does after a couple of heat cycles.

Thanks to all and for my Spanish friend....................................... que tomas una Aguila por tu salud de mi parte!!!! Saludos!!!

[Jdub]

You may be experiencing air in the system that will vent over time. However, I am sure that you have not removed the excess play from between the caliper piston and the brake pad as you have indicated.

Typically the puck will pull in further than you'd like due to new seals and the natural vacuum inherent in a closed fluid system where pushing something out means it will retract back to the original point.

I suggest you get the front in the air, pull the pads, and replace these pads with a block of wood or metal that is not quite as thick as your new pads. Force those pistons out via the brake pedal with several strong pushes to overcome the seals, return to the caliper, and remove the wood/metal. Then push the piston in JUST ENOUGH to get the new brake pad in. Do this for every caliper. This will remove

One more thing: any brake fluid on the outside/top of the MC, in the shallow "tray" area they provide? I have seen cracked MC caps that let the fluid leak out, and the pedal feel a bit mushy. Just a thought.

John

[RAM]

What I did to remove the excess play was remove the pads and replace them with the old pads (which were thinner) and pressed on the pedal until the pedal was hard. I then took the old pads out and replaced them with the new pads. I tried to only move the pistons back as little as possible to where I needed force the pads in. They are new pads with anti squeal pads so I needed to move the pistons back as much as possible. What do you think?

Ruben

[Jdub]

It's the anti-squeal pads. I tried to shoe those in too and it was a big NO-GO. The pads are the culprits for certain as, to get them in, you typically have to give yourself a bit more room.

Your options now are to 1)remove the antisqueals (most here have opinions about the stickon versus the brushon) or 2)just wait it out: over time the caliper pistons will move out and you will have a firmer pedal.

Up to you. I found that, even with judicious alignment of the piston cutout-to-rotor, I was squealing within 100 miles. Not much, but they do. I think this is some sort of badge of honor among Porsche owners!

John

[Craig]

RAM,
Another suggestion. I had to have the front calipers rebuilt on a 69 MGB I own. The pedal felt kind of mushy, lots of pedal travel, etc.
He said what I needed to do was to get the car up to about 60 mph, and then stop the car, using fairly firm pressure on the pedal. He said to do this about 4-5 times in a row, and this would help seat everything. I found a country road, and did this, and it really helped the pedal feel and travel. Don't push so hard that you come to a stop immediately, but don't coast to a stop either. I think the key is to let the pads wear against the rotors at a good speed, and keeping the pressure on the pedal firm and constant.
So find a straight country road and give it a try!
Craig
77 911s Coupe

[spinner]

RAM
Since you replaced the MC and rebuilt the calipers, the "spongy" feel is from trapped air. It takes several flushes to get all of the trapped air out. Drive the car around a little (no need to go fast) and then flush one more time. Go ahead and use a whole can of ATE.
Good luck.

Paul