Squishy brakes won't go away!

[GBC01]

Hey folks, I'm at a loss here with my brakes... Buckle up for my life story...

I've been dealing wish squishy brakes for about 2 years on my 98' C1500 Sierra, Just recently bought a livestock trailer, so I figured I should get on figuring out why my brakes were squishy since I'll have thousands of pounds of livestock behind my truck soon. About 3 years ago I had the ABS module, calipers, rotors, shoes and pads replaced on the truck. Just recently checked all of that and the pads/shoes look like new still. So everyone I've talked to so far has said it was the master cylinder leaking internally, so I just replaced it, the new doorman one was junk as well and began leaking for the gaskets out of the package, so I did the NBS upgrade like everyone said, bench bled it, bled the lines at the wheels, solid brake fluid, no air. STILL have squishy brakes! I then bought an Autel and did an ABS brake bleed, as well as bleeding everything at the wheel cylinders, STILL NOTHING. The brakes grab great once you've pushed hard enough on the pedal, but its the amount of travel in the pedal that concerns me. It sounds like I'm pushing down on a bag of air until the brakes start to grab. For a reference point, I get zero breaking power until my brake pedal is about even with my gas pedal (a fair amount of travel in my opinion).

So any suggestions on how to get rid of this spongy, squishy, cloud like brake pedal?
I've considered the brake booster to be suspect, but it doesn't seem to show the signs that a bad booster would show.

Thanks everyone!

 

[Gibson]

The first thing I would check is the adjustment of the rear brakes.
Too much shoe-to-drum clearance= lots of pedal travel before brakes take hold.
Remember, the front discs will do nothing until the rear shoes contact the drums.

 

[GBC01]

The first thing I would check is the adjustment of the rear brakes.
Too much shoe-to-drum clearance= lots of pedal travel before brakes take hold.
Remember, the front discs will do nothing until the rear shoes contact the drums.

Thanks for the suggestion, I'll give that a shot!

 

[Frank Enstein]

I like the Earl's Solo Bleed bleed screws. I have them on everything in my driveway. They are sold by size.

Brake Bleeders at Summit Racing

Shop brake bleeders, including speed bleeders, solo brake bleeders, and power brake bleeders at Summit Racing today. We’ve got the right brake bleeder in stock and ready to ship! <br />

www.summitracing.com

I highly recommend Braided PTFE (Teflon) flexible brake hoses. Make sure they are DOT approved!

WARNING! If you do these to your truck, you will do them on everything you own!

Two things that get overlooked;

1) Make sure the calipers float properly. Remove the pads an reinstall the calipers. Push the caliper in toward the center and out toward the outside of the truck.

If you can't make them slide with 1 finger they are stuck. Get some brake lube and clean and lubricate until they can be pushed with one finger (it can be a firm push).

2) Check the drum backing plates for grooves on the 3 raised pads where the brake shoes contact the backing plate. Smooth them flat (they may need to be welded/brazed or even replaced) and put a small amount of brake lube on the pads. You don't want any lube on the friction surface.

Clean and inspect/replace all the brake hardware and the adjusters. Lubricate the adjusters and make double sure they move freely. Adjust the rear brakes until a TINY amount of drag is felt. You may need to apply the brakes several times to center the shoes as you adjust them.

The rear drums typically use the parking brake to keep them adjusted. get in the habit of using the parking brake EVERY TIME you park! If the parking brake hasn't been used much (or ever!) make sure it will release while you still have the drums off and the shoes removed.

If you cannot use the parking brake the rear shoes may need to be manually adjusted from time to time.

After all that THEN look at the booster!

 

[Schurkey]

I've been dealing wish squishy brakes for about 2 years on my 98' C1500 Sierra,

Almost all "pickup" 1500s have horrible leading/trailing shoe rear drums. The mechanism stinks, and the brakes are just plain too small (254mm, "10 inches")

About 3 years ago I had the ABS module, calipers, rotors, shoes and pads replaced on the truck. Just recently checked all of that and the pads/shoes look like new still.

First Guess: ABS wasn't properly bled. But there's plenty of other potential problems, and Frank Enstein listed most of 'em.

doorman one was junk as well

Welcome to Dorman's "Made By Communists" entire product line. It's a rare thing to get quality parts from them. But then, my new AC-Delco master cylinder on my '97 K2500 was also Chinese. Dirtbags.

NBS upgrade like everyone said, bench bled it, bled the lines at the wheels, solid brake fluid, no air.

Your truck was almost certainly built with low-drag calipers. Unless you changed the calipers, too, YOU HAVE THE WRONG MASTER CYLINDER. IT WILL NEVER WORK RIGHT ON YOUR TRUCK. NEVER EVER, AMEN, SO LONG. The master cylinder bore is too large, a crappy work-around for not having the step-bore "third chamber" in the correct Quick Take-Up master cylinder. The so-called "NBS" master gives-up hydraulic advantage on the caliper and wheel-cylinder pistons

If the power booster fails, you'll need both feet and a squirt of adrenaline to stop the truck. Good luck if your wife or kid is driving.

Get a REAL (not Dorman) master cylinder for your truck based on the brake option code on the glovebox Service Parts Identification (SPID) decal in the glovebox. You probably have "JB5" brakes, but you should confirm. Could be JB6, I guess--which still has the low-drag calipers that need a Quick Take-up (3-chamber, step-bore) master cylinder.

I then bought an Autel and did an ABS brake bleed, as well as bleeding everything at the wheel cylinders, STILL NOTHING. The brakes grab great once you've pushed hard enough on the pedal, but its the amount of travel in the pedal that concerns me. It sounds like I'm pushing down on a bag of air until the brakes start to grab. For a reference point, I get zero breaking power until my brake pedal is about even with my gas pedal (a fair amount of travel in my opinion).

So any suggestions on how to get rid of this spongy, squishy, cloud like brake pedal?
I've considered the brake booster to be suspect, but it doesn't seem to show the signs that a bad booster would show.

If you really do have the common "10-inch" rear drums, you'll want to verify that they're properly adjusted.

The brake bleed procedure is attached (page 2.) Your Autel cycles the ABS four or six times...right? Not just once? Any ABS codes?

 

[81nascar]

From what you describe I would agree that it really sounds like the rears are out of adjustment or you still have more bleeding to do.. Some times it just take a bunch of times to get all the air out. Maybe double check the wheel cylinders for fluid weeping or overextended.. Unfortunately we are in an era that even "new" parts can be suspect anymore. You just can't take them for granted anymore.. but, you know that now..

 

[CNRED]

Just went through the same things. Replace the brake lines. They don't leak but break down internally. Eventually the hoses will get so bad they retain the brake fluid and will not allow the calipers to lift off the rotors.

 

[CrustyJunker]

Sounds like you did everything the right way by the book without getting creative. Also a +1 on maybe trying new brake hoses or upgrading to the fancy braided ones? That would be the only other culprit that's not exotic or expensive.

 

[bluetahoe]

I have jb6 brakes with the larger drums for towing. I went through similar issues for years trying different things. I went completely through using top shelf products. They are awesome brakes now!!! I tow a boat and other utility trailers.
1. If you have not, change your rubber brake lines out.
2. Definitely change your booster--it's old and could easily have a small leak developing.
3. Most people don't tighten the brake shoes tight enough. It's a really big problem that is often overlooked.
4. Once you get the peddle feel right. If you still need more brakes I have found the upgrade to jb6 rears is the best option since rear shoes do a lot of work and the larger ones are great.

Good Luck