pgtr

Looking at pictures of early C3 master cylinder #5455509 for manual (non-power) brakes...

1. The #5455509 had bleeders right above the outlet lines. I'm assuming these function for bench bleeding purposes? Whether on the car or on the bench - that would be super-convenient... (and see follow-on question 3 below)

2. What is the bore diameter on the #5455509 brake cylinder used on non-power brake early C3s?

3. Generic question - bench bleeding a typical master cylinder (w/o extra bleeders as above). After bench bleeding - when disconnecting the bleeder lines and connecting the actual brake lines - don't you always re-introduce a little air? Clarify that step?

HeadsU.P.

Part 3.
Yes, when you disconnect the kit from the MC, a bubble or two is always introduced into the system front & rear before you can attach the brake lines. Its unavoidable.
So the entire vehicle has to be bled. All six bleeder screws.

Part 1. Rumor has it that the MC with attached bleeder screws was for the assembly line. Only certain yrs had that design.

calwldlife

when installing m/c apply pedal force and crack open lines that attach to m/c one at a time to remove any air.
use rag to control fluid that will come out.

stingr69

Bleeder screws on the factory master cylinder are used on the production line to fill the system but not used in service.

Replacement master cylinders many times do not have them. Some rebuilt GM master cylinders will obviously have them but you dont use those screws for anything.

pgtr

OK Thanks. If you have (or install) one of the early/older M/Cs that has the 2 built-in bleeder screws above the 2 outlet lines - I'm not seeing any reason one couldn't hook short tubes from those bleeders back into the reservoirs and essentially 'bench bleed' the brakes after installed in car (or any time you like). Seems like that might be an advantage potentially for having/using those old-style M/Cs.

pgtr

Out of curiosity anybody know what the bore diameter is on the 509 manual brake M/C on early C3s? Thx

HeadsU.P.

pgtr,
I don't believe that's how it works. Maybe. IDK

I believe those bleeders are inlets not outlets. So, air is still behind the brake-line fittings.

MelWff

1. You would have to block the outlet ports so no point.
2. Bore is 1"
3. After attaching the lines you can crack the bleed screws to bleed any that got in to the master but still have to bleed all 4 calipers.

pgtr

1" got it - thanks.

I was thinking that the outlet lines would essentially be 'blocked' if hooked up to the calipers. Further (assuming bleeders are tapped into same outlet lines) was thinking any air bubbles exiting the M/C outlets would travel 'up' and thus out the M/C bleeders.

thx again

HeadsU.P.

Looks good on paper.
Murphys Law says otherwise.

ZIPP IT

I have been told it is 1" on manual brakes

pspicci

And if your were going to try and "bench bleed" the MC on the car you will need to make sure the back of the MC is higher than the front of the MC to make sure you get all the air bubbles out - by jacking up the rear of the car.

Pat

cagotzmann

Bench bleed the MC as best you can, then try this. I have been doing this for many years.

Get the last bit of air out from the brake master cylinder. - CorvetteForum - Chevrolet Corvette Forum Discussion