Clutch and Brake Bleeding Techniques

[Dan Cordon]

Good point Todd! Some people prefer to put brake fluid in the cup just 
to be safe. Once you try it though, you'll see that the amount of flow 
going out the tube is substantial. And by the time you've got new fluid 
coming out, the cup is mostly full of brake fluid anyway. And while it's 
possible for water in the cup to diffuse up the tube, I can't imagine it 
happening faster than the bleeder valve gets closed. I suppose if one 
took a nap between bleeding the system and closing the valve..... :o)

Anyone know the rate of diffusion of water in brake fluid?

But...if you're concerned you can always start it out with a 1/2" of 
brake fluid in the cup instead.

Todd Young wrote:

> I personally think this is a good way to introduce water into the brake 
> hydraulic system, but that's just my opinion.
> 
> Personally, I would just go out and buy the "one man brake bleeding 
> tool" that Lisle makes. Works good, has a one way valve at one end that 
> serves the same purpose without worrying about introducing water vapor 
> to the brake system.
> 
> Dan Cordon wrote:
> 
>> With all the talk about clutch bleeding, I thought I'd share my 
>> technique that I use for bleeding systems. I've used this on brakes 
>> for dozens of cars, and even a few months ago on my audi clutch (after 
>> MC rebuild).
>>
>> Below is a link (sorry for the length) to a picture I made of the 
>> setup. Really, you just need a clear piece of tubing that fits snugly 
>> over the bleeder valve and a cup of water. You can use non-clear 
>> tubing, but it's not as cool :o)
>>
>> 1) Press one end of the tubing over the bleeder valve.
>> 2) Place the other end of the tubing hose below the water in the cup
>> 3) Open the bleeder valve
>> 4) Depress (or have friend do it while you watch) clutch/brake pedal a 
>> few times. Keep reservoir topped off. Continue bleeding until fluid 
>> coming out hose is clear.
>> 5) Close bleeder valve
>> 6) Repeat for other circuits if necessary.
>>
>> http://www.its2.uidaho.edu/cordon/dan/images/car_images/brake_bleeding.jpg 
>>
>>
>> The key to making this work is keeping the end of the hose in the 
>> fluid. By doing this, the cylinder will draw fluid from the reservoir 
>> *instead* of sucking it up the hose.
>>
>> NOTE: In this setup, fluid in NOT drawn from the cup. It's just used 
>> as an means to keep air from drawing back in to the cylinder.
>>
>> I've done this by myself many times with success, though I prefer to 
>> have another person operating the pedal. This way I can watch things 
>> to tell when they've cleared up and close the valve quickly when done.
>>
>> Also, when doing my clutch circuit, I couldn't get any other method to 
>> work. This way worked great.
>>
> 

-- 
Dan Cordon
Mechanical Engineer
University of Idaho - Engine Research Facility