VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 brake bleeding- long run first?

Just a very simple question: I intend to use my vacuum bleeder to get the air out of the lines on my 38. What is the consensus on which wheel to do first, the longest line or the shortest???
i have replaced everything so the system is full of air. filled the master a day or so ago and have let it drain down once with all the bleeders open, kinda like priming the pump. seems i have heard or read somewhere to go to the farthest wheel first. maybe it doesnt matter at all?

You have your instructions correct. Go to the farthermost wheel and work up to the shortest.

Also before you hook up the Mity Vac, loosen each bleeder and pump the brake fluid down each line , and out all over the floor, to get most of the air and debris out, the opening in the bleeder valve is very small when just screwed out a half or quarter turn and the vacuum pump won't suck dirt and debris out it will plug the small opening, especially if you didn't replace the rusty steel lines and the old rubber hoses, refill the master cylinder then hook up the Mity Vac and start the vacuum process. I have found the vacuum pump does not force the fluid down the system as well as the pumping of the peddle will, and if you pull too much of a vacuum air bubbles may show up because it will be sucked around where the plastic tubing attaches to the bleeder valve. That has been my experiance.

Ray and Mack: I've got brakes! bleeding was no problem, followed both your recommendation. spilled brake fluid took the paint off my nicely painted master cylinder though. i had forgotten brake fluids paint stripping ability.
I used the Mity vacs rubber 90 degree connectors, first time because of clearance issue. they work better than hooking the plastic tubing direct as far as air leaks go. it makes a nice tight seal.
steve

Great, now I'll let you drive behind me. HA!

I have found pumping the peddle a better way of bleeding as it doesnot allow the air bubbles time to float to high parts of the lines. If you use a clear plastic line between bleeder screw and the loose end into brake fluid it can be done as a 1 man operation. The clear hose allows u to see any air bubbles exiting the cylinder.
With some vehicles (morris mini in particular) I have found the most sucessful way is to pump fluid in through the bleeder screws and drain the excess out of master cylinder resevour.

The method of reverse pressure bleeding is not a bad idea!
Eastwood is currently marketing a new reverse pressure bleeding kit.

DON"T USE REVERSE bleeding on any car with A B S
that's an EXPENSIVE mistake!!!

Tom are you meaning Anti-Skid Brakes?

ABS= anti-lock brake system ABS uses a series of solenoids valves and a pump to regulate brake pressure in panic stop situations.
There are close tolerances involved and contaminates such as rust and rubber particles in the brake fluid can ruin parts if pushed back into them.
The valves are so sensitive to contamination that you should not push the caliper pistons back in without opening the bleeder valves first.
I would be very concerned about reverse bleeding an ABS system and plugging up some very expensive parts and possibly compromising the car or trucks ability to stop.
It is also Important to flush the brake system as per Maintenance schedule! It can save you some MAJOR expense down the road!

Well Tom, that is frightening to hear...I guess I have just been lucky by changeing the pads by pushing the pistons back in with a "C" clamp, I never have opened a bleeder valve on the disc brakes during a pad replacement job, I probably will start doing that..... It does displace a good amount of fluid back up into the reservoir of the master cylinder, I usually suck most of it out before starting the job with a Mity-Vac vacuum pump.
Thanks for shareing the information...

Tom 32
You are right about reverse bleeding abs system. When changing pads on abs fitted vehicles I clamp the hose and open bleeder to retract the piston for that reason. I only mentioned reverse bleeding as a option having found it beneficial especially on some british vehicles the bleed nipple is at the lower portion of the wheel cylinder (a*** up with care poms) but have not found this problem on any other vehicles.
Tony

I have seen more than one brake system messed up by forcing brake fluid back up into the master cyl one was a 93 caddy, $1900.00 later we finally got good brakes! also had a problem on a 96 chev pickup we were able to get the garbage flushed out of that one.