Very Spongy Brakes, '03 GMC Sierra, New Parts Too.

[Turk]

Would like your input on what could be causing the brakes to be VERY spongy on my
(Bought New) '03 GMC Sierra with 188,000. 5.3L 4x4. Not driven a lot anymore.

It has been spongy "before & after" the following maintenance:

* Rear ceramic pads, rotors, calipers & e-brake pads 1,000 miles ago.

* Amsoil DOT 3 Synthetic Brake Fluid 10,000 miles ago.

* Front ceramic brake pads & rotors 22,000 miles ago.

I even hear a "PSSHHhhhhhh" when I push them hard.

The only things I'm thinking is either the front Calipers, or I need to go "bed them in"
with 8-9 60MPH to 3-5MPH stops in a row.

I pull a 3,000 Lb Boat and it's slow to stop with just the truck, let alone having the Boat on.

Quite concerned about it not stopping safely.

Thanks!

 

[edyvw]

What is manufacturer of those pads and rotors?
Strictly ceramic brakes are OK if your priority are clean wheels.
However, if your priority is stopping power, then you need some ceramic/carbon combination.
I was experimenting with a lot of pads and rotors, found that Brembo rotors work best, and EBC pads. Though EBC rotors are also extremely good.

 

[Turk]

Front & rear rotors are NAPA Ultra Premium. Pads are NAPA's top quality Surestop I think?

Really don't want to replace those again so soon.....

 

[NHGUY]

If he pads are "Tru Stop" they are Napa's lowest priced offering,hailing from China.

 

[dishdude]

Did you try bleeding the brakes?

 

[Turk]

Originally Posted By: NHGUY
If he pads are "Tru Stop" they are Napa's lowest priced offering,hailing from China.


Nope, not those for sure, sorry about that. I forgot/got confused on the name. That was one I replaced on a different car.

Adaptive I think?

 

[Turk]

Originally Posted By: dishdude
Did you try bleeding the brakes?


Yes! That was with the new Amsoil DOT 3 10,000 miles ago.
I thought it would cure this but it didn't!

 

[eljefino]

If you screw up a bleeding (eg it runs dry) you may need to bench bleed the master cylinder and/or ABS unit.

 

[SuperDave456]

It's not driven much anymore, but it's been 10,000 miles since you bled the system?

I bleed my truck every 2 years.
I can tell a significant difference when towing.

If it's been over a year, and you don't drive it much except to tow. Then you should probably bleed the breaks once a year.

Do what I do and grab your significant other and use it as a team building exercise.

 

[Turk]

Originally Posted By: SuperDave456
It's not driven much anymore, but it's been 10,000 miles since you bled the system?

I bleed my truck every 2 years.
I can tell a significant difference when towing.

If it's been over a year, and you don't drive it much except to tow. Then you should probably bleed the breaks once a year.

Do what I do and grab your significant other and use it as a team building exercise.


It's been about 1 1/2 years since I put in the Amsoil Syn brake fluid.

As mentioned above, it was not better immediately after the brake bleeding.

I'm thinking I should try the bedding procedure, right?

 

[901Memphis]

Any severe rust on the brake lines? My Buick had a slow leak almost undetectable at first but it was letting air into the system causing spongy feel which bleeding can't cure. Yours is an 03 though I believe it should be the first year with rust coat on the steel.

 

[Merkava_4]

If you tried reusing the old banjo washers on the front caliper hoses, that could be your problem. They are one time use washers.

Another possibility is the rear caliper pistons aren't dialed out far enough. You want those dialed out as far as you can and yet still be able to swing the pads over the rotors.

Piston seals in the master cylinder might be letting fluid slide by. When that happens, you'll get a soft pedal but no leak.

 

[Turk]

Originally Posted By: 901Memphis
Any severe rust on the brake lines? My Buick had a slow leak almost undetectable at first but it was letting air into the system causing spongy feel which bleeding can't cure. Yours is an 03 though I believe it should be the first year with rust coat on the steel.


No, I just looked, they're really not too bad. Very light surface rust in spots, that's all.

 

[ToadU]

Check the hydra boost unit located behind the master cylinder. GMs infamous hydro boost could be the cause. Cheapest place is roackauto for a new one.

 

[Turk]

Originally Posted By: Merkava_4
If you tried reusing the old banjo washers on the front caliper hoses, that could be your problem. They are one time use washers.

Another possibility is the rear caliper pistons aren't dialed out far enough. You want those dialed out as far as you can and yet still be able to swing the pads over the rotors.

Piston seals in the master cylinder might be letting fluid slide by. When that happens, you'll get a soft pedal but no leak.


Front calipers were not replaced.

The new rear calipers are set-up fine.

MC piston seals sounds interesting... Could be.

 

[clinebarger]

Originally Posted By: ToadU
Check the hydra boost unit located behind the master cylinder. GMs infamous hydro boost could be the cause. Cheapest place is roackauto for a new one.


I think his truck has a Vacuum Brake Booster, What is this about the infamous GM Hydro-Boost? They are actually a Saginaw part & used on Dodges as well, They are on par with the Bendix HB units found on Fords.

The GM '99-'04 1500 trucks have pretty dismal brakes, Mostly caused by the undersized rear disc's that is magnified if you have the light duty thin rotors. Trucks with a towing package have thicker rotors.

Ceramic pads wear good & don't dust down wheels, But "bite" to stop a loaded truck they do not have! Try some Wagner Severe Duty semi metallic pads.

 

[01rangerxl]

Does the truck have Hydroboost or vacuum boost?

If it's vacuum boost, take off the check valve/hose, and dip something that will show liquid down into the booster. If you see liquid on the "dipstick," brake fluid is leaking into the booster from the MC.

 

[The Critic]

Find someone with access to a scan tool that can perform the "automated bleed" function. If that doesn't solve it, then perhaps its time for a new master cyl.

 

[Turk]

Originally Posted By: clinebarger


The GM '99-'04 1500 trucks have pretty dismal brakes, Mostly caused by the undersized rear disc's that is magnified if you have the light duty thin rotors. Trucks with a towing package have thicker rotors.

Ceramic pads wear good & don't dust down wheels, But "bite" to stop a loaded truck they do not have! Try some Wagner Severe Duty semi metallic pads.



My 1500 has the Towing Package.

 

[Turk]

Originally Posted By: The Critic
Find someone with access to a scan tool that can perform the "automated bleed" function. If that doesn't solve it, then perhaps its time for a new master cyl.


Ok, will do. Going to bed them in first, just because, lol.

The pedal goes pretty far to the floor without a lot of stopping power,
so it may be a MC, etc.

I'll get more Amsoil Brake Fluid; I want the good stuff in!