Lousy brakes on my 1999 4x4 pickup

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chrisinestes

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What can I do about the terrible brakes on my truck? The pedel squishes to the floor. I've replaced the master cylinder, rotors, & pads & ABS module... and they are only slightly better. It's been properly bled several times. There are no leaks. The wheels are OEM. The tires aren't over-sized. It's like the master cylinder isn't pushing enough fluid to the calipers. Is there a master cyilinder that pushes a larger volume of fluid?

Any ideas for me?
Chris
 
well two things come to mind
Frist are the rear brakes adjusted properly. if not then that will give you a poor brake pedal.

Are the brake calipers on correctly (Bleeder valves up) see them on the wrong sides many times. Can't remove all the air if there on wrong.

Also can you build a pedal if you pump it 2 or 3 times?

Also check and make sure front caliper slides are free and not frozen
 
Find another mechanic. The one you are using is not qualified as it appears he is only throwing parts at it in hopes of fixing it.
 
happy 2011 said:
well two things come to mind
Frist are the rear brakes adjusted properly. if not then that will give you a poor brake pedal.

Are the brake calipers on correctly (Bleeder valves up) see them on the wrong sides many times. Can't remove all the air if there on wrong.

Also can you build a pedal if you pump it 2 or 3 times?

Also check and make sure front caliper slides are free and not frozen
Click to expand...


How would one make sure the rear brakes are adjusted correctly? It all went together smoothly and the calipers move freely both front and rear. I and my GM mechanic have looked it over and they are together correctly.

The bleeders are pointing up. Would they even fit backwards?

Pumping doesn't build any better pedal feel or braking.

I just learned that there is a Steering Angle Sensor in the steering column. I'm told that if it's mis-adjusted or not working, it will limit the pressure to the calipers because, for full pressure, it want's the wheels straight. Have you heard of that?

What about old, soft, expanding brakes hoses? Are they swelling and not letting full pressure to the calipers?

Thanks!
Chris
 
Z15 said:
Find another mechanic. The one you are using is not qualified as it appears he is only throwing parts at it in hopes of fixing it.
Click to expand...

Yeah, it does look like that's what's happening.

It was me that started throwng parts at it... the new rotors, brake pads, and the master cyinder. The pads and rotors were worn and needed replaced. Replacing them didn't make the brakes any better, though. I'm guessing the only money wasted on it was the master cylinder... but who knows?

The ABS module was bad and was setting a code. Replacing it eliminated the codes, but didn't make a difference on the braking.

What I'm trying to do now is avoiding throwing parts at it... that gets expensive! Haha
 
Z15 said:
If everything is new (not junky rebuilt's) and the pedal goes to the floor the first suspicion is air in the brake fluid.

See if this gives you any ideas http://www.popularmechanics.com/cars/how-to/maintenance/4213448
Click to expand...

You're right... it feels exactly like there is air in the system. It's been bled and bled and bled and bench bled and bled and autobled with the scan tool... If there is air in there, it's hiding, and I don't know how to find it...

Any ideas?
 
apply the parking brake, and see if the pedal is normal ?

if it is.. there is a problem with the rear brakes...

if the pedal still sinks to the floor.. i would guess faulty master cyl
 
It sure feels like there is air in the system, but it's been bled over and over again. Bench bled, manually bled, and bled with the scan tool many times.

I engaged the e-brake, and the pedal feels the same. The rear brakes are disc, but the rear e-brakes are drum... so I don't know how that would affect the brake pedal. It's had 2 new master cylinders, but I guess that doesn't mean I didn't get 2 bad ones in a row. How would I isolate the master cylinder and test that?

Thanks!
Chris
 
chrisinestes said:
It sure feels like there is air in the system, but it's been bled over and over again. Bench bled, manually bled, and bled with the scan tool many times.

I engaged the e-brake, and the pedal feels the same. The rear brakes are disc, but the rear e-brakes are drum... so I don't know how that would affect the brake pedal. It's had 2 new master cylinders, but I guess that doesn't mean I didn't get 2 bad ones in a row. How would I isolate the master cylinder and test that?

Thanks!
Chris
Click to expand...

Hey there,

correct if you have shoe in hat style rear disc brakes... aplying the parking brake will do nothing... sorry wasnt sure of the configurations.. i thought it would be internal caliper style parking brake...

stupid question, did you bench bleed the master before putting it on sounds like you did? did you try just gravity bleeding all 4 corners ??? i find at the end of the day gravity bleed works best... takes the longest but does the job.

it almost seems like your ABS is doing something funky to ya!

cheers
Warts
 
Wartsnuff said:
Hey there,

correct if you have shoe in hat style rear disc brakes... aplying the parking brake will do nothing... sorry wasnt sure of the configurations.. i thought it would be internal caliper style parking brake...

stupid question, did you bench bleed the master before putting it on sounds like you did? did you try just gravity bleeding all 4 corners ??? i find at the end of the day gravity bleed works best... takes the longest but does the job.

it almost seems like your ABS is doing something funky to ya!

cheers
Warts
Click to expand...

Me again... Sorry I missed this post so long ago. I didn't have my notifications set like I thunk'd I did.

I still have the mushy brakes.

Pumping the pedal makes no difference in pedal feel, or brake function.

The master cyl has been bench bled a couple times. Since the last time I posted, it's been power bled/auto bled again. No change. The ABS system seems to be working correctly. If I'm on ice, and "test" the brakes, all 4 corners seem to cycle.

I did put some high end braided steel flex lines in. That did actually take a small, but noticeable amount of mush out.

I haven't gravity bled them, but I've been told that it wouldn't work with my ABS system. Would it work? Could it hurt to try it? I'd hate to let a bubble in and have to pay to have the Auto Bleed done again. Would it also bleed the air out of the master cyl if somehow there was some trapped in there?

Thanks!
Chris
 
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