Install new master cylinder without bleeding?

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How about bench bleeding on the car? Thats how I did mine about 6 years ago using one of the cheap parts store m/c bleed kits. Picture before I filled the reservoirs.

Edit: I still bled the entire system since I changed from a single pot m/c to a dual.

IMG_20150603_151629.jpg
 
You can bench bleed the MS bolted to the car if it's level where it bolts to the firewall.
 
66fyssh said:
How about bench bleeding on the car? Thats how I did mine about 6 years ago using one of the cheap parts store m/c bleed kits. Picture before I filled the reservoirs.

Edit: I still bled the entire system since I changed from a single pot m/c to a dual.

View attachment 1715666086
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Perfectly fine as long as it sits level.
 
Demonracer said:
Do you "really" want to take the chance of installing a new master cylinder WITHOUT bleeding the brakes? Come on folks, these older cars of ours are not being produced any longer. If you bang it up because of not taking the short amount of time to bleed the system, then you will spend untold amounts of time fixing the car, if it's repairable. I personally would never install a master cylinder without bleeding the system, better safe than sorry.
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I would also add that this is the perfect time to get the majority of the old fluid out of the lines. You need to do it periodically anyway.
 
:rofl:Yes! I'm so dumb, I have them up front in my Ragtop and didn't even remember.:BangHead:
Definitely a good way to go.
 
I have pulled this off at least 3 times in my life. It depends on how the vehicle is built IE how much room you have to work and how the lines are routed IE you want the master end of the tubes to be the highest points. If the lines are so routed that they go above the master fittings end, you are likely screwed.

As Rusty said, bleed the master, and be CAREFUL that you get it FULLY bled. Cap it, seal the ports and try and "tip" it so the ports (while capped) are "up", screw the lines in, lightly tighten, then use what flex there is in the tubes and install the master mechanically. Put a pan/ rags etc under the master and bleed there at those fittings by cracking the fittings. You either need two people or an adjustable "push stick" to put pressure on the pedal against the seat hardware

You must be careful and thoughtful and methodical. "Sometimes" it works
 
Look inside the new one, you will see how its shaped inside,like where a ring would seat.
Some replacements came with push rod.
 
Got it out! Whew.
Okay, I bench bled, and I pushed the pedal slightly till the air was done coming out of the lines than I had my helper hold the pedal and I tightened the fittings down! The pedal feels normal, I think I pulled it off!!
So, how full do we keep the master cylinder?
 
3/4 to 1” from top if master sits pretty level.
 
Sounds like you figured it out, congratulations!
The reason you had so much trouble bleeding the whole system before was because you hadn't bled the master cylinder first!
And my current method doesn't require a helper, just a piece of clear hose, and a bottle you can suspend ABOVE the bleeder screws. Open the bleeder, get back behind the wheel and slowly pump the brake pedal.
The air bubbles want to rise in the tube, keep pumping till bubbles stop, close bleeder, go to next bleeder.
Don't let master run out of fluid, or you'll have to start over.
 
sccachallenger said:
Sounds like you figured it out, congratulations!
The reason you had so much trouble bleeding the whole system before was because you hadn't bled the master cylinder first!
And my current method doesn't require a helper, just a piece of clear hose, and a bottle you can suspend ABOVE the bleeder screws. Open the bleeder, get back behind the wheel and slowly pump the brake pedal.
The air bubbles want to rise in the tube, keep pumping till bubbles stop, close bleeder, go to next bleeder.
Don't let master run out of fluid, or you'll have to start over.
Click to expand...
Yeah, it was a nightmare bleeding it without bleeding the master cylinder first!

I will try that bleeding trick next time I bleed them!
 
swingingdart said:
If its fuller than that will it want to leak out?
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Tooljunkie said:
Some leak, some dont. Where the rubber sits on master,if the casting is machine finish smooth, it shouldnt leak.
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I take the master cylinder apart and flat file the cap sealing surface until it’s smooth.
Then flush it out and reassemble.
It’s worth it to not have it seep all over the master.
 
If you bench bleed the master cylinder off the car, you can visibly confirm it is bled correctly and functioning properly before installation.
 
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