|
CAUSE
|
REASON
|
|
1.
Bleeder screws on calipers not on top.
|
1. The bleeder screws on calipers
must be at the 12:00 position on the caliper to allow all the
air to escape during bleeding. A very common mistake installers
will make is to reverse the side the caliper goes on giving you
a situation where the caliper bleeder screw is facing down. It's
also common to use the wrong caliper on a bolt on disc kit giving
a situation a situation where the bleeder hole is shifted from
the 12:00 position producing a pocket of air at the top of the
caliper bore which can not be dislodged. Check your bleeder hole
orientation.
|
|
2.
A defective master cylinder which does not hold pressure.
|
2. If brake fluid bypasses a pressure
seal on the master cylinder you get a pedal that fades. To test
for this obtain two inverted flare plugs at an auto parts store
and plug both master cylinder outlets. Try your pedal. If the
pedal is high and firm the master cylinder is good. If the pedal
faces the master is bad. Replace master as necessary.
|
|
3.
No residual pressure valve to rear drum brakes.
|
3. Drum braked require the use
of a 10 lb residual pressure valve in the line. This residual
pressure counter balances the drum brake spring tension keeping
the shoes close to the drums. This results in a higher firmer
pedal. You can test this by clamping off the rear hose removing
the rear drums from the system. Now test your pedal. If the pedal
gets better you will need to splice a 10 lb residual pressure
valve into the rear line.
|
|
4.
Hard line that loops up.
|
4. Hard brake line that loops up
and then back down will tend to trap air. It doesn't take much
air to cause problems so check your line carefully.
|
| 5.
Incorrect master cylinder. |
5. If the bore of the
master cylinder is too small for the fluid requirements of the system
you will get a very poor pedal. This will happen most frequently
with four piston calipers and with four wheel disc brakes. The only
solution for this is to install a larger bore master cylinder of
a true four wheel disc master. |
| 6.
Incorrectly bled or adjusted rear calipers. |
6. Rear calipers that
have an internal parking brake with a lever can be troublesome.
These calipers must be adjusted so that the piston is moved out
and the pads are close to the rotor. If this initial adjustment
is not made the pistons will travel outward during activation but
no squeezing of the rotor will occur. This can be checked by clamping
off the rear hoses and checking if the pedal gets better. Adjust
as necessary. |
| 7.
Incorrect booster pin length. |
7. The booster pin that
pushes on the master cylinder must almost be touching the master
cylinder piston face. A gap larger than 1/32" will begin to
introduce a spongy pedal. Adjust as necessary. |
| 8.
Silicone brake fluid. |
8. While silicone fluid is great because it does
not attack paint it also aerates very easily and can give a spongy
pedal.
NOTE: If you heat the silicone brake fluid to
250 degrees, it will get rid of the spongy pedal.
|
| 9.
Rear wheel cylinders too large. |
9. Rear drum wheel cylinders
that are too large will give a poor pedal. Check as in step six
above. |
| 10.
Loose front wheel bearings. |
10. Loose front wheel bearings
will cause rotor wobble. This will cause the caliper pistons to
retract too far into the caliper giving a spongy pedal every time
you hit the brakes. Check and adjust as necessary. |
Cart: 0 items, $0.00 
