is it necessary to bench bleed the master cylinder even though i will be bleeding all 4 corners after installing master cylinder?

 

you don't have to bench bleed, but but there's alot of air which gets trapped in the MC if you don't bench bleed it 1st; plus you'll go through 2-3 bottles of brake fluid if you don't bench bleed it (without bench bleeding it will seem like no matter how much you bleed all 4 corners, they'll def be air with bubbles in your brake system & seem like it'll never **** pure fluid into the bottle).

bench bleeding makes your life easier, just fill the master cylinder with fluid, have someone hold it over an oil pan while you push the piston (i use the back of a screwdriver) and wait for all the bubbles to come out of its ports. have plenty of rags, brake fluid will eat through paint, then bolt your freshly bench bled master cylinder on to the brake master booster & its the hardlines with a flare wrench. then proceed to bleed the calipers.

 

my understnading is that if you dont bench bleed then its gonna take MUCH longer to bleed the corners and may even be impossible to remove all air from the system. bench bleeding is pretty simple and im sure you could find a kit with fittings at a local hardware store

 

If you don't bench bleed it. you won't feel pressure on your brake pedal until you do. that's my $0.02

 

what if i dont have a vise bench

 

if you don't have a bench vise...

there's also kits w/ fittings you can buy at any auto parts store which attach to the MC and re-circulate the fluid coming out the ports back into the master cylinder to bench bleed it. same idea, you push the rod in the back of the MC until it is free of air & no bubbles show up in the fluid

* remember to remove the old rubber seal and replace it with the new one provided with your new master cylinder

 

the new seal goes over the rod on the brake booster?

 

pic from www.acuraautomotiveparts.org:

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(#4)

with the master cylinder removed, you'll be able to see the rod that pushes the piston in the m/c. if the seal didn't come off with the master cylinder, it could be stuck around the pushrod or sticking onto the brake booster. you'll need to remove this seal, your master cylinder should come with a new seal since you'll be replacing it.

 

and the seal would be number 4 in that picture right?

 

Bench-bleeding is so important that if you read the paperwork that came with your new master cylinder, it says that not bench-bleeding your new master cylinder will VOID your warranty. The kit is very cheap-under $10 and only takes a few minutes. Good luck!!

 

You must bench bleed. If you don't, you won't get all of the microbubbles out of the master cylinder itself.

You don't need a bench vise. You just need to push the piston in on the mc. You can use anything to do that. I believe that I used a blunt tip screwdriver and leaned into a wall as it takes quite a bit of pressure to push the piston in. Still took a good 30+ minutes before I was satisified that all of the air was out of the mc.

Many that have tried to avoid bench bleeding either ended up goign through multiple bleeding sessions and liters of brake fluid, or gave up and pulled the mc to bench bleed it.

 

if it bleeds we can kill it.

 

When bench bleeding a MC, why do you have to actually remove it from the vehicle? Doesnt pressing the brake pedal do the same thing as pushing in on the cylindar when its in a bench vice?