My wife's Cabriolet needs a new Master Cylinder and I have one. The Bentley manual does not mention doing a bench bleed for the MC. It says to just bolt it on and bleed the brakes.
The MC did not come with a bench bleeding kit and I haven't been able to locate one locally.
What say you?
If the manual doesn't say to bleed it, do what the manual says. Usually if a bench bleed is required it will be in the instructions.
Bench bleeding is something that sounds great in theory, but doesn't work nearly so well in reality. Plus it tends to make a heck of a mess.
So I don't do it any longer. I may do a firewall bleed by cracking the fittings. But after that, it's a conventional at the wheels bleeding. Less mess and faster.
I've never bench bled a master, old or new car and foxtrapper is right about the mess. I really never had a problem with good brakes after a conventional bleeding.
^What they said. Never thought it was worth it. The bore of most master cylinders doesn't really push that much air through the lines anyway.
Clutch or brake? If it's clutch, have you considered reverse bleeding?
Cactus wrote: Clutch or brake? If it's clutch, have you considered reverse bleeding?
Brake
Ok, thanks. I was worried about the mess. Sounds bleeding it on the car will work out fine.
My only bench bleed consisted of putting some fluid in it. Hold a finger over the outlet port. Pump until fluid pushes finger off the port. Install master cylinder.
This has worked for umpteen MC''s.
iceracer wrote: My only bench bleed consisted of putting some fluid in it. Hold a finger over the outlet port. Pump until fluid pushes finger off the port. Install master cylinder. This has worked for umpteen MC''s.
This.
You guys are all dead wrong. I can bench bleed a master cylinder, without the bleeding kit, install it, and have a perfect pedal without ever cracking a bleeder screw at the wheels. Vice, fingertips and a screwdriver are all you need.
All you are going to do if you don't bench bleed it is fill the brake lines with air that doesn't need to be there. If your excuse is that you want to flush all the old fluid out anyway, you are still wrong. It is far, far easier to push the old fluid out if there is no air in the lines.
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