2001 Silverado Brake Pedal


Paul94Z28
10-15-2007, 09:42 AM
Hi Board-

Interesting issue with a 01 Silverado. Brakes are fine, except when cornering hard and pedal goes to the floor. Seriously, no other issues.

I am thinking master cylinder.

Any thoughts?

MT-2500
10-15-2007, 09:50 AM
Hi Board-

Interesting issue with a 01 Silverado. Brakes are fine, except when cornering hard and pedal goes to the floor. Seriously, no other issues.

I am thinking master cylinder.

Any thoughts?

Odd operation.
Any abs brake lights?
I would get a scanner on it and check abs brake operation.
MT

HanibalTheCannibal
10-15-2007, 10:54 AM
Hard cornering+braking= drifting?

Weird issue. I have the same truck and I havent experienced that. A loss of vacuum could cause the mooshy pedal

silverado122775
10-15-2007, 11:37 AM
That is strange, but maybe the preasure of the turn and braking is cause a line to open up somewhere. Have you checked the level of your brake fluid?

j cAT
10-23-2007, 07:07 PM
check for proper level in brake res. if ok, bleed brakes, could be air in brake system.

Paul94Z28
01-25-2008, 10:22 PM
Thanks - will try it.

SLJ2137694
01-26-2008, 11:16 AM
Hi Board-

Interesting issue with a 01 Silverado. Brakes are fine, except when cornering hard and pedal goes to the floor. Seriously, no other issues.

I am thinking master cylinder.

Any thoughts?
Could you be getting an activation of the ABS system? Deactivate the ABS by pulling a fuse and see if the pedal drops in the same circumstances. Do this carefully where you won't hit anything, you will still have normal brakes. It is common to feel something in the brake pedal on many ABS systems when they are working. A loss of vacuum will give you a hard pedal.

Paul94Z28
10-20-2008, 09:38 PM
Replaced the wheel bearing and the issue has gone away.

I do not completely understand why.

SLJ2137694
10-20-2008, 11:16 PM
Replaced the wheel bearing and the issue has gone away.

I do not completely understand why.

The new wheel bearing probably came with a new ABS sensor in it. I would say you were getting a false activation of the ABS system due to a wheel speed sensor issue or bad reluctor ring in the wheel bearing. This is why I previously asked you to deactivate the ABS and see if you still had the problem. If the problem went away and your base brakes were fine that points to an ABS problem. Now do you understand?

j cAT
10-21-2008, 11:00 AM
The new wheel bearing probably came with a new ABS sensor in it. I would say you were getting a false activation of the ABS system due to a wheel speed sensor issue or bad reluctor ring in the wheel bearing. This is why I previously asked you to deactivate the ABS and see if you still had the problem. If the problem went away and your base brakes were fine that points to an ABS problem. Now do you understand?


If this wheel bearing replacement solved this brake pedal to floor issue , I would say that the ABS is defective...If it were an ABS sensor issue the pedal would not go to floor but pulse ..if abs was ok....

since the bearing was replaced , this then corrected the sensor output voltage, which then stopped the ABS from activating, in a mode which is improper..


as everyone knows these vehicles have a very poorly designed sensor mounting issue... the rust forces the sensor out of range. this then causes the sensor output to fall below 300MV AC...this is when the ABS will activate and start pulsing..

the reason I am geting into this is because if one is out of range I'm sure the other sensor is ready to soon act up..the way to check is to locate the output conector at sensor and with a meter measure for 500MV DC with the wheel rotating...


also the abs should be tested for proper operation...

SLJ2137694
10-21-2008, 11:45 AM
In my 20+ years handling brakes for General Motors Corporation, I have learned from talking to hundreds of consumers and technicians that many times, when the ABS activates at an unexpected time or when it is getting a false signal and it gives a false ABS cycle, the driver states the brake pedal went to the floor. In these cases of a false cycle, fixing the cause of the false cycle will take care of the complaint and there is nothing wrong with the system that would give a real "pedal to the floor" complaint. In these cases worrying about the rest of the system is a waste of time and money. If a component fixed a false activation and there were no other legitimate complaints with the system, I would leave it alone. As for testing the ABS, the system goes through a self test on each key cycle. If a sensor tests within parameters but occasionally drops a signal or reports a wrong speed, the system thinks it is operating correctly and does not set a code, but the complaint could be "pedal to the floor" or a comment on the ABS working when it normally would not activate.

Wayne60
10-21-2008, 03:34 PM
Are there any real cons to permanently disconnecting the ABS system ?

I'm going from a 92 to an 01 and don't like the feel of the pedal.

Thanks.

MT-2500
10-21-2008, 04:17 PM
Are there any real cons to permanently disconnecting the ABS system ?

I'm going from a 92 to an 01 and don't like the feel of the pedal.

Thanks.

It is a safety big safety issue.
And illegal to do it.
It could turn you in to a con.
If it resulted in a bad accident and the right lawyer and judge got on to the fact you did it.

j cAT
10-21-2008, 05:13 PM
In my 20+ years handling brakes for General Motors Corporation, I have learned from talking to hundreds of consumers and technicians that many times, when the ABS activates at an unexpected time or when it is getting a false signal and it gives a false ABS cycle, the driver states the brake pedal went to the floor. In these cases of a false cycle, fixing the cause of the false cycle will take care of the complaint and there is nothing wrong with the system that would give a real "pedal to the floor" complaint. In these cases worrying about the rest of the system is a waste of time and money. If a component fixed a false activation and there were no other legitimate complaints with the system, I would leave it alone. As for testing the ABS, the system goes through a self test on each key cycle. If a sensor tests within parameters but occasionally drops a signal or reports a wrong speed, the system thinks it is operating correctly and does not set a code, but the complaint could be "pedal to the floor" or a comment on the ABS working when it normally would not activate.



this reported problem was pedal to floor...replaced front wheel bearing and the problem is solved.....


If the sensor output was dropping out for more that 15millisec... then the abs should activate... this would mean pulsating brake pedal....not pedal to floor...


If the ABS has an excessive dump/isolation time this would cause the symptom of pedal to floor...


If this were my vehicle I would make sure that when the wheels lock up that the ABS is pulsating....if not there is a problem.. need DTC...

j cAT
10-21-2008, 05:31 PM
Are there any real cons to permanently disconnecting the ABS system ?

I'm going from a 92 to an 01 and don't like the feel of the pedal.

Thanks.

If you don't like the pedal feel, this would not be an ABS issue...this is usually a simple brake fluid replacement...the new brake fluid will give better /higher pressures to the pads...


It could be other componets also , but this is the most common answer..

in 1992 GM used a better higher quality caliper ...the 2001 is suseptible to corrosive road chemicals.

Wayne60
10-21-2008, 06:27 PM
It could be other componets also , but this is the most common answer..

in 1992 GM used a better higher quality caliper ...the 2001 is suseptible to corrosive road chemicals.

Very good info. :cheers: Now the about 01 caliper what are the symptons of corrosion, some kind of binding ?

Thanks.

j cAT
10-21-2008, 06:39 PM
Very good info. :cheers: Now the about 01 caliper what are the symptons of corrosion, some kind of binding ?

Thanks.

you have a very poor /cheap/low quality pin,caliper weather dust boots...and the tolerances are very variable...this means that the pads/caliper pins may fit very tight and start binding on install....

If you live in a wet/snow climate you will find the pins rust to siezure in a very short time..


my 1996 and the other older vehicles never had this occur...no wonder GM is not long for this world...

Wayne60
10-22-2008, 10:41 AM
How about swapping the front rotors and calipers to the 1500HD units,
I was reading that the 1500HD trucks received larger rotors that perform better.

SLJ2137694
10-22-2008, 11:26 AM
this reported problem was pedal to floor...replaced front wheel bearing and the problem is solved.....


If the sensor output was dropping out for more that 15millisec... then the abs should activate... this would mean pulsating brake pedal....not pedal to floor...


If the ABS has an excessive dump/isolation time this would cause the symptom of pedal to floor...


If this were my vehicle I would make sure that when the wheels lock up that the ABS is pulsating....if not there is a problem.. need DTC...

I think you keep missing the point! Many times an unexpected false ABS cycle is perceived by the driver to be a "pedal to the floor" complaint. Many drivers don't know how the pedal feels during an ABS activation. I have chased too many of these complaints only to find that what actually happened was an ABS activation and the pedal moves. Since the pedal moved and it wasn't expected it must have gone to the floor! Try to fix that! Always investigate the possability of an ABS activation, either a legitamate activation or a false cycle before you start chasing a possability that the pedal did go to the floor due to an internal hydraulic problem.
ALSO, how does new fluid give higher/better pressure to the pads? Is there more to this you need to mention?

Wayne60
10-22-2008, 11:40 AM
Here is a great article regarding the fluid


http://www.babcox.com/editorial/bf/bf50412.htm

j cAT
10-22-2008, 03:54 PM
I can't say what happened with what this vehicle owner felt...I can only say many times ABS havs activated with me driving and I never had pedal to floor...

The only time's I had pedal to floor was when the brake line ruptured at the point were there was a rust bubble...Should be s/steel lines on all vehicles..


as far as the brake fluid I'm surprised that you are not aware or maybe your playing with me on my extensive knowledge concerning brake fluids and contamination...


these fluids need be replaced periodicly...especially the fluid in the calipers as the heat and moisture change the fluid so that it does not compress as new fluid would...

I used to measure this pressure many times over many years and new clean uncontaiminated fluid always produces the correct car builders designed pressure..

ABS systems are very sensitive to bad fluid...


only this guy knows what his brake fluid looks like and he's not talking..

Wayne60
10-22-2008, 03:59 PM
How about swapping the front rotors and calipers to the 1500HD units



Any thoughts on this approach ?


Thanks,
Wayne

j cAT
10-22-2008, 04:06 PM
Here is a great article regarding the fluid


http://www.babcox.com/editorial/bf/bf50412.htm

wayne thanks for that site on brake fluid....the vehicle I once owned for 17 years had no brake componet failures all original at 380,000mi then I sold it....I got my monies worth ....I did periodicy replace the brake fluid....always on a very dry warm day...I suggest that , as this article stated not to believe the big 3 or should I say little 3 that brake fluid should last the life of the vehicle....


but to be fair as we all know these vehicles are to be scrapped at 100,000mi and 7 years...because that is the little 3 automakers life expectency......


funny how mercedes recommends to replace brake fluid every year..but GM states it's good for the vehicle's life...

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