pedal slowly hits floor after new front brakes?

[benoit454]

Well guys I started out today buying new rotors, pads, seals, and bearings for the front of the 84 c10.

We had no clue which J brake system we had so we tok in an old rotor to match up. Then got the rest afterwards. Well I'm thinking it's jb3, not sure, got the jb1 or jb3 rotor, matched up with ours, same height, thickness, diameter.

Get home, try and compres the OLD yes, old calipers, to put the pads in and they are pretty hard to compress with my c clamp. Well After that the DS was fully compressed, and went on ok, the PS might not have been FULLY compressed, but it was a PITA to get on, very tough, like I needed it pressed in more lol.

Anyways, once on, you could barely get the rotors to turn by hand, they would but tough.

Then we go to try out the brakes....

YEA not good..

The pedal went to the floor, yet had resistance to it. Not like when you got a blown line or cylinder or something, or when you have air in the line, had some resistance or pressure to it, but just dropped until it hit the floor.

Now I'm not sure if they stopped the truck good or not, we only moved it out from under the carport, and dad was driving, he said the pedal just felt weird to him.

I call autozone, where I bought the stuff, they say master cylinder.

I don't know, kinda weird it was fine now it's just gone, from sitting?

What would you guys think?

Booster?

Master cylinder?

Caliper?

or maybe a hose?

I plan on checking it out tomorrow and buying what I need to fix it. But would like opinions on what you guys think?

or if there's a for sure way to narrow it down to a caliper, MC, or booster?

[knightlife]

I'd have to say check fluid level first
then hoses
then cracks around master cylinder
if fluid but no cracks, it just needs a new seal

hell..you might even have a cracked caliper...possibilities are endless brother!

just make a list of possibilities...and work your way down...that usually helps eliminate a lot of fuss

[Pyrotechnic]

I bought a rebuilt master cylinder and it was defective right out of the box. Sometimes I would barely touch the brakes and it would be like I was standing on them, and other times the pedal would slowly go down to the floor and I'd have to pump it to get more pressure. Very scary. Turns out I was getting almost no pressure to the rear as well.

Brought it back, and asked if they had a NEW cylinder. It was only 3 dollars more. Kinda pissed me off that they didn't tell me the new part was available and that it was not much more the first time.

[Ivan D.]

Chris, if there ain't no external fluid leaks my vote goes for an internal leak inside the master cylinder - the old master cylinder in my Lincoln did just that, stops the car just fine but eventually loses pressure when sitting at a light, a new master cylinder fixed it good. I put rebuilt master cylinders in both my car and my truck, got the ones done by some Canadian company, they're just fine.

[benoit454]

Thanks, as far as I know there are no external leaks anywhere. I don't get the brake light coming on anytime, and haven't sen any fluid leaks anyweres.

The pedal doesn't feel like it does when you get an external leak either.

I've never felt one with an internal leak though.

[FlatBrokeRacing]

If one of your calipers was hard to compress with a c-clamp, That is where I would start. Plus it is not out of the question that the rubber line is either too old or worn out internally.

[benoit454]

Well BOTH calipers were hard to push in.

Guys I went out and tried it today and it seemed like with the engine off after a couple pumps they got hard, and stayed hard as they should be.

But as soon as I started it up, they were just like yesterday, and pumping didn't help any.

Shut it off and tried it again, seemed to be hard, pedal went down maybe an inch if that and got hard.

[Ivan D.]

replace the master cylinder, they are like $20 remanufactured anyways, $30 or less new

[benoit454]

More like $30-35 reman. and $40-50 new.


Anyways I went back out, moved in back in the carport, freaking things working fine.

That's after I went down and bought 2 new calipers. But oh well I put them on anyways.

Just came in to grab a bite to eat, gotta go back out and bleed them. If I have anymore problems with it it's time for a new master cylinder for sure.

[benoit454]

Ok put on the new calipers, took it out for a ride.

Alot better pedal then before, hard as it should be and not bleed off going to the floor, by hard I mean it stops and stays there, doesn't continue to drop like it was.

No shake, no shimmy, no vibration at all.


Felt great.

Either a wheel bearing was gone, loose, or warped, caliper was sticking and barely hitting, or rotor was warped because that shake and pull to the driver's side is gone.

Brakes ae all broken in good and bedded correctly, and she stops great.

[68GMC454]

glad to hear you got it fixed...

[benoit454]

Yea hopefully it doesn't come back.

[Ivan D.]

good brakes are always nice to have - the only old (and by old I mean not installed by me) parts of my brakes are now the rear wheel cylinders and pads and axle lines - I have brand new rotors, bearings, calipers, and pads up front, new hoses, new lines everywhere, new master cylinder, and new manual proportioning valve, and all that is powered by a hydro-boost unit off a 1-ton diesel Now I only need shocks, cause when I lay on the brakes it dives so hard in the front that on one occasion the rear wheels lifted off the ground!

[knightlife]

wewt wewt! glad to hear that you got her fixed...had me worried bout ur safety breh

[benoit454]

Yea only thing not changed on our brakes now is 1 wheel cylinder, all the hoses and lines are old, MC, booster, and prop. valve are old, rest is new.

We need shocks too, lol it still rides great but they are so old the top part is rusted and has holes. The tube I guess you call it that covers the chrome arm of the shock. They haven't leaked any oil out that I know of yet.

[Ivan D.]

that tube is just a protective cover, most shocks have them in plastic now, and some don't even have them no more, I wouldn't worry about it too much as long as the shock's body is intact

[benoit454]

Yea that's what I was thinking. it rides ok but you can tell they are worn out, probably gm 1984 shocks lol.