[Vwdiesel] Was: brake bleeding hell on a VW bug-Drumbrake overheating

[Tony and Lillie]

I never thought about the fluid expanding. I guess taht makes sense.

On the trucks, they use more compressed air to engage the brakes. IE, the 
pressure goes up as you apply the brakes. This is for the service brakes 
only. The parking brakes use a spring brake setup, in which a spring pulls 
the brakes into contact. The air pressure that's applied and stored in the 
tank pulls against that spring, releasing the parking brake function. So, in 
essence, it uses the depletion of air to work the parking brake, while it 
uses the application of air to work the service brakes.

BTW, when I lost the brakes on the truck, it was clearly that there was no 
contact whatsoever. They slowly went away, but when gone, there was nothing 
whatsoever. It was nothing like when I've had a severe recuction in braking 
on the track due to overheated pads and rotors.

Oh, and that was when I was much younger and more foolish. Thenkfully I was 
at the end of a very long downgrade, and I lived to tell the story. These 
days, I don't even rely on the brakes when going downhill. Ahhhh, to 
remember the days of youth and foolishness.........

Tony
----- Original Message ----- 
Subject: Re: [Vwdiesel] Was: brake bleeding hell on a VW bug-Drumbrake 
overheating


> One thing to remember is that cars use brake fluid, which expands and
> adds pressure (applying the brakes more) as it heats up, while big rigs
> and other air brake vehicles use air (And increasing pressure just keeps
> the brakes from being applied).
>
> Air brakes use the /loss/ of pressure to appy the brakes, so increasing
> the pressure in the line from heat expansion of the air won't apply the
> brakes and lock them up.
>
> -Kurt