Can I bleed the master cylinder using the car?

Status
Not open for further replies.
Joined
Jan 20, 2017
Messages
922
Location
NJ
I need to replace my master cylinder.

The instructions say to bench bleed by filling and using tubing pumping the brake fluid back into the master cylinder by pushing the rod with your hand.

I've always bled it on the car. I bled it the same way, disconnectimg tje brake lines and hooking up tubing to re-use the new brake fluid by funneling back into the master cylinder, same as in a vise.

I find it easier for my wife to pump the brake pedal and me watch the "operation" under the hood.

Then when bled, I hook up the lines and do the normal bleeding of each wheel until the brake fluid comes clear in a clear soda bottle with a hose attached from the bleeder screw.

Anything wrong with this method?
 
Nothing wrong with your method. Supposedly bench bleeding became popular when a lot of cars had the master cylinders mounted low on the frame.

Just take care to not get brake fluid on the paint and if you think you might have run a bunch of water all over the area, obviously with the master cylinder cap on.
 
Last edited:
It is Not recommended to do it that way. There is little feeling for what is going on, and you can, under some circumstances ruin the rubber cups inside the master cyl. Bench bleed ing is required prior to installation.
 
If the part says you have to, you have to. They wouldn't spend the nickle on that plastic tube if you didn't need it.

Most likely your car's MC tilts backward at the firewall and there'd be no way to get at the air bubble on the far forward side of your particular unit.

Other MCs you've dealt with have had a more vertical firewall.

Some MCs are tapped for a line at the far forward end; yours does not sound like one.

IOW, just follow the directions.
laugh.gif
 
Until the innards are immersed in brake fluid, they are dry and stiff. A bench bleed will ease the rubber into duty. Here's a tip, All the hydraulic parts come with instructions. Reading them a few times will help you get the idea, if you've never played with one before.
grin2.gif
 
I bench bleed. I do it to make sure the MC goes full stroke. Can you be sure the brake pedal makes the MC go all the way? Also i can watch and see when the air bubbles stop.
 
I rig an air lock, a little brake fluid in a hot sauce bottle and 2' of clear tubing sized to make a tight fit at the bleeder. Once you don't see bubbles,you move on. It is cheap and you don't need help. If you can't bleed, it is because the system is sucking air some where. Now you have to get a gravity bleed running. A system won't gravity bleed if it isn't air tight.
 
Status
Not open for further replies.
Back
Top