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big2bird
09-29-2008, 01:57 AM
So, since I am going to change my master cylinder next week, and have a pressure bleeder, do I really need to bench bleed the master? I know Gary does, but is it really necessary with a pressure bleeder? (Gary has a neat method of doing it BTW)

TimAT
09-29-2008, 02:26 AM
One way or the other, the air in the M/C is going to be pushed out. It'll take less fluid to do it on the bench. My thought is why push any more air thru the whole system than absolutly necessary.

tracdogg2
09-29-2008, 04:55 PM
Unless you buy the early master with the two bleeders on it you will never push all the air out, on-car or bench-bleeding. Simple physics. The air must exit thru the return port in the resevoir.
Bench bleed: Mount the master in a vise tilting front end down. Bleed as usual.
On-car bleed: Raise rear of car until master is pointing downhill. It normally sits uphill. Bleed as usual, gravity or pressure.
This is why they put the bleeders on the PB cars.
Mike

kwplot34
09-30-2008, 08:00 AM
Now Jeff,why would you want to push all that air through the system :bonkers:
Just bench bleed them and do it right,it's not hard and takes just a few minutes of you're time :oh:
Don't make me get on a plane and fly out there and smack you around :crap:

turtlevette
10-05-2008, 06:18 PM
why don't any of you guys like to experiment. I'd like to know if the pressure bleeder would do the trick.

give it a try Jeff.

Twin_Turbo
10-05-2008, 06:46 PM
Yes, bench bleed it with the nose of the MC pointing DOWN!!!! This is the only way to get all the bubbles out via the little hole to the reservoir. You can put as much pressure on the system as you like, with the stock mounting & the MC pointing up you will NEVER get the air out.

010752
10-05-2008, 07:19 PM
I never bench bleed and use higher pressure to flush first, then use lower pressure to bleed.

Even if you bench bleed first you will always have air when making the line connections at the mc.

You are supposed to flush the system regularily anyway, but few ever do. Gets rid of a lot of sludge. Take a look at the old master. I doubt you really want that crap in the system.

Twin_Turbo
10-05-2008, 07:21 PM
Yes, sure there will be air where you hook up the lines but it won't be in the piston bore where it will stay trapped.

big2bird
10-05-2008, 07:31 PM
Well, I made up some brake lines to return the fluid to the reservoirs, and return them below the fluid level. I could not believe how long to expel all the air. It must have taken 20 pumps to get it all. I installed it, then used the pressure bleeder to flush the car.
No air in that system. Still not completely happy though, and not much left to check.
I took pictures, but left out the memory card.:banghead:

010752
10-05-2008, 07:31 PM
What I meant was that all the lines will have to be bled completely anyway.

From some of the posts above, it implied to bleed the master, install and you're good to go, saving a lot of fluid.

Twin_Turbo
10-05-2008, 07:57 PM
Well, I made up some brake lines to return the fluid to the reservoirs, and return them below the fluid level. I could not believe how long to expel all the air. It must have taken 20 pumps to get it all. I installed it, then used the pressure bleeder to flush the car.
No air in that system. Still not completely happy though, and not much left to check.
I took pictures, but left out the memory card.:banghead:


Pics most likely ended up in camera memory, you can probably move them to the mem stick if you insert one.

big2bird
10-05-2008, 08:14 PM
Pics most likely ended up in camera memory, you can probably move them to the mem stick if you insert one.

No images.:cussing:

Twin_Turbo
10-05-2008, 09:53 PM
Dumbass :D

big2bird
10-06-2008, 01:04 AM
Dumbass :D

More than I care to admit.:noob:

saudivette
10-06-2008, 07:59 AM
I bench bled my master cylinder after I powder coated it but then I pulled it apart again for someone who asked for assembly pictures of a master cylinder. It wasn't until I had it back on the car and was just about to start bleeding the brakes that I remembered that I hadn't bench bled it again after pulling it apart.

I filled the master cylinder with fluid and had my son sit in the car and pump the pedal. I was able to stand over and watch the bubbles coming out of the holes in the bottom of each reservoir. It took a few minutes until there were no more bubbles coming out at all so I carried on and bled the brakes with my Motive bleeder. I haven't had the car running yet so not %100 certain on how good the brakes will be but I can't imagine there'll be too much (if any) air left in the master cylinder...

turtlevette
10-10-2008, 12:07 AM
Well, I made up some brake lines to return the fluid to the reservoirs, and return them below the fluid level. I could not believe how long to expel all the air. It must have taken 20 pumps to get it all. I installed it, then used the pressure bleeder to flush the car.
No air in that system. Still not completely happy though, and not much left to check.
I took pictures, but left out the memory card.:banghead:

no balls. None of you ffers ever take a chance on anything. I bet that power bleeder would have blasted all the air out. Now we won't know until someone with balls gives it a try. I guess i'll have to do it.

How come the pedal is still low? Did you figure anything out?

mrvette
10-10-2008, 02:15 AM
I bet that lo pedal is not anyting but a bad booster....I fought my '72 for years and finally switched....easy swap and it cured the problem....car stops on a dime and I can lock the brakes easy anytime now.....no defected noted in the old stock booster either.....

:bonkers::crap:design problem is all I can say, as I never pulled a line on the m/cyl during the swap....I wanted a direct A-B comparo....

:yahoo: