PattiR

After replacing the brakes and lines all around on my 1957 Corvette, the last thing I need to do is mount the new (repro) master cylinder and bleed the brakes.
My question is since I'm using a pressure bleed pump, do I need to bench bleed the Master Cylinder first?

Thanks,

Dennis

Matt Gruber

since the lines are dry, the mc fluid will empty into the lines anyway.
I've never used a pressure bleeder in 40 yrs on my 61 or anything else, so hopefully a user will chime in.

MikeM

No.

ragtop00

I'm doing my 62 next week. All new system like yours. Open all 4 bleeders and fill the master. Keep an eye on the MC fluid level and your bleeder tubes. Should be done with the gravity bleed in about 30 min..
Mike

6D2148

But bench bleed m/c first

jimh_1962

bench bleed the mc. Then bleed the rest of the lines using a mity vac. If you used ss lines then prepare to reseat the fittings more than once. It is easier if you have more than one person so you can have someone check the lines for leaks while bleeding the brakes.

MikeM

The factory didn't bench bleed the MC first. Why would you rookies bench bleed it. They just pressure filled and called it good.

Sometime later, they did a Evac/fill process but there still was no MC bench bleed.

jim lockwood

I've never bench bled a master cylinder and I've always gotten away with it.

In fact, until I joined this forum, I didn't know I had to. Now that I know I've been doing it wrong, I probably can't get away with it any more.

Jim

PattiR

For everyone to be clear and provide any other information, here is what I am doing.
I bought a pressure brake filling pump from Corvette Central. It has a fitted MC cap with a hose going to it from a large plastic bottle holding the brake fluid which will pressurize the system with 5-10lbs psi. I thought that this would be a good way to both fill the MC w/o having to bench bleed it and let me have a look for any leaks in my brake lines at the same time so I could seal them up.
Has any one else done this?
Any ideas would be welcome.

Again, thanks for all the ideas.

Dennis

MikeM

See post #2.

The factory pressure bled the brakes through the MC fill opening without bench bleeding the MC. No reason you can't either.

They even did it without opening any bleeder screws.

Frankie the Fink

I've never understood the big deal with bleeding brakes on any old car. I've done it for 50 years on all types of cars with no problems. No mini-vacs, no pressure bleeders, just me, a brake bleeder wrench, a can of brake fluid and a monkey to pump the pedal when I tell them to. Its all of a 20 minute job...

Changed more than a few master cylinders out and done upgrades to dual master cylinders - no bench bleeding either.

vettsplit 63

I have seen disaster happen when someone forgot to bleed the pressure off of the adaptor cap before removing it. Old style lacquer paint and brake fluid don't interact well. BC/CC you can probably get away with it, but why take the chance.

PattiR

Oh Yeah! the instructions on the pressure bleeder were quite specific about this . I don't want to add any refinishing work to this job. The outside of this car is beautiful(imho), and I want it to stay that way.

Thanks to all for the info and suggestions.
If anyone can think of any thing else please let me know.

Thanks,

Dennis

MikeM

Yeah, turn off yer computer and go bleed the brakes and quit worrying about it.

PattiR

MikeM,

Thanks to you and everyone who gave me good advice on this issue.

And Mike, you were up for the Oscar for Best Economic Use of the English Language in a Discussion Format, but frankly, your last post was just too wordy!

Regards,

Dennis

rfn026

I just replaced the m/c on my '58. My pressure bleeder wouldn't fit so I did it the old fashioned way with 2 people. I ran denatured alcohol through the system to get rid of the silicone fluid and then used the Ford high-performance DOT 3 fluid (Amazon.com).

I didn't bench bleed the m/c. Everything worked out fine.

Richard Newton
The New Master Cylinder

DUB

Dennis,
To answer this question:"Has any one else done this?"

YES..I use my brake pressure bleeder whenever I do brakes. Mine allows the pressures to be higher than what you posted. I can go as high as 20psi for the C4 cars that require it as the manual somewhat states.

My pressure bleeder a has a bladder that keeps the air pressure separate from the fluid.

When I do dual reservoir master cylinders....sometimes I will bench bleed them...sometimes I do not. but either way....when the system is under pressure and I have the car in a position that makes the master cylinder LEVEL...I will slowly press the brake pedal a few times when the a bleeder is open flowing out fluid to actuate the master cylinder...and this is due to the circuitry in the dual master cylinders...I want to make sure not small air bubbles are lingering around.

Then...if the system was flushed out or new lines installed an they are dry.. I shock the frame so any small bubbles sticking to the inner walls of the tubing will release...much like the bubbles on the inside of your glass of 7-Up when you tap it.

If you are dealing with a single reservoir master cylinder..you should only have to press the brake pedal a few times when bleeding the rear brakes and not have to do it when you do the front because there is only one reservoir that does the brake system...unlike a dual master cylinder...when I have to do it twice...once for the rear and then once for the front brakes. Then make sure you give the time needed so if any bubbles were in the master cylinder area...they can have time to come out.

DUB