Brake Pedal question ...

[eliems]

For the last couple of weeks there have been infrequent times when I go to brake and the pedal goes farther (sometimes much farther) toward the floor before it applies.

The fluid was up but dirty so I had it flushed and changed. Pads are 35% all around and no leaks. No air in the system either.

Still feeling this with the pedal though. It will stay pumped for most of a drive and then suprises me again.

Master cylindar is letting fluid by? (IF so do you guys replace or rebuild the Master)?

Booster loses pressure? (What is that like to fix)?

Thanks.

 

[AZTVR]

A test for master cylinder internal leak is to apply light continuous pressure to the pedal while you are stopped. IThe pedal should hold position. If it slowly lowers, you have an internal leak. That might not show up in normal use where you apply short strong pressure.

(It seems to me that the booster would only affect amount of pressure required rather than pedal position; but, I don't have that much experience to say.)

 

[RTTTTed]

The clutch pedal assy has a plastic bushing on the shaft - does the pedal move or have any sideplay? Could it be posible that you have a brakefluid boiling problem?

AZTVR mentioned the booster and he has a point - check the rubber grommet to see if it's cracked or if there are any vacuum leaks in the booster circuit. Actually, you should check the engine vacuum as well.

Ted

 

[eliems]

Negative on sideways movement of the pedal it feels tight, just depresses too far at times. Not likely to be a boiing issue as new fluid and this happens when the car is running cold as well. Also never happened until last couple of weeks.

Continuous pressure on the pedal and it stays firm.

How do I check the vacuum? (Sorry, no expert mechanic here)

 

[ViperGTS]

Not good.
I had once a cylinder tilted & stuck in the brake caliper causing similar issues in my Jeep....as soon as the brake fluid starts to boil you get the "brake pedal to the floor feeling".

 

[ViperGeorge]

Your brake pads should be lightly riding on the rotors. When you apply brake pressure the pads don't have to move very far to begin braking action. If your pads get knocked back so that there is a larger than normal air gap between the pads and the rotors then more movement of the brake pedal is necessary to close the gap and begin braking action. This can happen because of loose or worn components at one or more of the wheels, loose/worn wheel bearings, severely warped rotor, or possibly some other things. I had your symptoms happen on another car (non-Viper) and it turned out to be bad bearings in the rear. Slight axle movement in the rear, especially when turning, allowed the rotors to move enough to kick the pads in. Very disconcerting.

I would do the static master cylinder test as described above and would also check each corner for loose or worn components that might cause pad knock back.

 

[RTTTTed]

Usually you use a vacuum or a Boost guage and check the idle vacuum. You could listen for air hissing noises at the vacuum lines on the engine. Look for disconected vac lines or missing plugs.

Not sure the year of your car. ABS problem possibly?

Otherwise, I would replace the Master Cylinder because they're not usually to expensive. Ask a Mechanic which cars use the same Master Cylinder as your Viper and price check.

I am assuming that you jacked up each corner, removed the wheels and inspected the brakes. Also inspect the E brake assys and cables (it still works normal?).

Ted

 

[eliems]

If your pads get knocked back so that there is a larger than normal air gap between the pads and the rotors then more movement of the brake pedal is necessary to close the gap and begin braking action. This can happen because of loose or worn components at one or more of the wheels,

Bingo, I tested this theory by observing if the pedal position changes when going around a curve to the right and nothing, then a curve to the left and sure enough the pedal depresses farther after turning hard to the left. This must mean that the pad is getting compressed when the car leans. Should be right wheel ... bearings? ball joint? could be a loose brake component?

If it is bearings or ball joint, what is the parts and labor like for those jobs?

 

[ViperGeorge]

See if you can tell which wheel is causing the pad knock back. Not sure what the prices would be, would you do it yourself? On my 06 coupe I had the rear hubs (including bearings) and rear tie rods replaced under warranty. The hubs were something like $700 each. If one side is bad I would replace both sides.