Brake pedal goes right to the floor!

[The_Handier_Man1]

From: floatdust  (Original Message)
Sent: 2/9/2003 10:02 PM

does any one know what might be wrong with my brakes? i have no pedal.
this is on a 75 cheiftain.



From: skypilot
Sent: 2/10/2003 9:48 AM

Floatdust, you've either got a Master cylinder that's gone out, a wheel cylinder that has gone out, or a brake line broke.
                              Skypilot



From: neil
Sent: 2/10/2003 10:40 AM

Check the level of brake fluid in the reservoir. If it's very low or empty you most likely have a leak. Leaks are usually visible on the inside of the wheels if it's a wheel cylinder or on the ground under the brake lines.If no leaks are found it's probably the master cylinder. Normaly if it is a master cylinder you should feel a spongy response on the brake pedal.



From: denison
Sent: 2/10/2003 2:35 PM

If you find visible leaks that is doubtless where the problem is. If you don’t find leaks --- you might have air that has been sucked into the system by cold temperatures. Does it get much below freezing where you live, and was it a long while since the brakes were bled? In such conditions ice crystals can form in a wheel cylinder or piston, lift the lip of the seal, and allow air to be drawn in. When it warms up the ice melts, the seal reseals itself, and even though the fluid expands, the air is still trapped in there. Even if no fluid got out this can happen. If you start with the wheel cylinders and are able to bleed the air out, be sure and continue to bleed the system enough to have clean fluid coming out at all wheel cylinders and caliper pistons. If you do this and the pedal still isn’t doing as it should - you might have air in the master cylinder, or in the boosters if you have separate ones. I don’t know about 75s, Does your rv have the booster powered by the power steering fluid, or by manifold vacuum?
If bleeding from the wheel cylinders doesn’t work, I would try bleeding from the master cylinder, to make sure I have fluid pressure at that point. Bleeding should be done when it is above freezing, or ice might remain inside. The guts of the master cylinder might be sticking, but should free up with clean fluid and temperatures where any ice would melt. By the way - when you replace a master cylinder, the book says to bench bleed it to get all of the air bubbles out before you bolt it into the rv - and they mean ALL. When I got my winny in 91, it was 19 years old, old enough that I just began replacing brakes parts even though they weren’t leaking. Now 12 years later I am thinking of doing it again - in order to enjoy another 12 years of reliable brake operation.         And let us know the outcome please!!!            denison