NEW - HISSING NOISE UNDER DASH

[timvasqz]

when there is a leak in the park brake release system some place, the spring
brake release valve on the dash passes air all the while the valve knob is
pushed-in/brake released.
If there is hissing under the dash when the park brake is pushed in /released
then it may be a leak in the spring brake can and the noise you hear is air
constantly passing the dash valve to fill or attempt to fill the springbrake
release diaphram which is leaking at the wheel. If you handel the valve that is
making the noise with wet fingers and feel no escaping air, where the air exits
out may be the problem part.

spring brake pumpkin looking things are under $80 each and $100. to have
installed by a mobile tech. They are one of those items that dont last forever
and time,not use is a reason to replace. You can rebuild the cans and replace
the diaphrams but the DOT likes to see new appliances installed when inspections
are made.

I believe the 91 RoyalConversion that Burnt up in Texas a year or so ago was the
result of a leaking springbrake can.

On another note. Often, When I park my bus/truck on a hill or an incline, I
release the park spring valve then pump the service brakes to deplete the air to
under 50 psi. This will put the air supply too low to release the brake
accidentally. I always fear a novis getting it to play trucker and hitting the
release valve by mistake.

One other fear of mine is setting the park brake on an incline and loosing air
in the suspension but not the tag. I wonder if the bus would roll down hill
riding on the inflated tag as the drive axle holds the brakes? I've had my
dumptruck skid down a steep dirt hill dragging the one axle that holds the
spring brakes.

Greg of Tim&Greg
94ptca