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Master Cylinder install question for my 66

66NICK98

Well-known member
Joined
Nov 24, 2004
Messages
47
Location
New Jersey
Corvette
1966 Blue Conv, 1998 Black Conv.
Hi there-

The new master cylinder I just received from Ecklers has a rubber boot on it and I would like to know if I keep it on the cylinder throughout the installation or do I remove it at some point and then reinstall it.

If you have any additional installation tips I would appreciate it...according to the service manual it seems pretty straight forward....disconnect the brake fluid line and then unbolt the cylinder...then install the new gasket and new cylinder. Is it that straight forward?

I was experiencing a soft brake pedal and had the line bled and new
synthetic fluid put in which appeared to do the trick for a couple of drives
then I noticed the pedal went soft again and the master cylinder had no fluid in it which led to the discovery that the cylinder was leaking inside the car at the point of the rubber boot or where the brake pedal engages
the master cylinder.

Any insights or suggestions are very much appreciated.

Thanks for your help,

Nick
 
Hi there-

The new master cylinder I just received from Ecklers has a rubber boot on it and I would like to know if I keep it on the cylinder throughout the installation or do I remove it at some point and then reinstall it.

If you have any additional installation tips I would appreciate it...according to the service manual it seems pretty straight forward....disconnect the brake fluid line and then unbolt the cylinder...then install the new gasket and new cylinder. Is it that straight forward?Nick

The boot stays with the new master cylinder - it keeps dirt and dust away from the bore seal surface that's exposed at the rear of the cylinder when the pedal is depressed.

You'll need to bench-bleed the new cylinder before you install it to get the air out of the bore, then bleed the system again after installation to get the air out of the lines. A typical bench-bleed setup is shown in the photo below. :)

BenchBleed650.jpg
 
Thank you JohnZ for your response...can I however install the cylinder and just bleed the
fluid into a container instead of the setup shown in your reply?
 
Thank you JohnZ for your response...can I however install the cylinder and just bleed the
fluid into a container instead of the setup shown in your reply?

No, you can't. You need to get the air out of the bore of the master cylinder first, before you install it on the car, if you expect to get a good pedal when bleeding the entire system; that's what bench-bleeding does.

:beer
 
Well, I bought the bench bleeding kit and was all set to proceed but when I took the new master cylinder out of the package a small piece of paper came with it which said
"WARNING, due to the OEM design on this cylinder, you should not attempt to bench bleed prior to installation. THIS ITEM SHOULD BE PRESSUE BLED OR VACUUM BLED ONLY"

I am at a loss to see why this should be. It looks like I will have to install the cylinder then bleed each wheel.

Thanks
 
Vacuum bleeding is a method of connecting a device to the open bleeders on the calipers and drawing brake fluid through the system until all air is gone.

Pressure bleeding mounts a cover on the master cylinder and brake fluid is forced through the system from pressurizing the reservoir. This is not the same as pumping the pedal which can mix air bubbles in with the fluid and result in never getting a proper pedal feel.

You can get a hand operated vacuum bleeder at most parts stores fairly cheap and this is probably the easiest way to do it. Just keep the reservoir full so you don't draw in any air and the fluid will flow in without any churning or bubbling.

I would bench bleed just to be sure there is no air pocket in the MC and then finish with vacuum bleeding after it's mounted. I don't see any way bench bleeding could harm the MC

Tom
 
Well, I bought the bench bleeding kit and was all set to proceed but when I took the new master cylinder out of the package a small piece of paper came with it which said
"WARNING, due to the OEM design on this cylinder, you should not attempt to bench bleed prior to installation. THIS ITEM SHOULD BE PRESSUE BLED OR VACUUM BLED ONLY"

I am at a loss to see why this should be. It looks like I will have to install the cylinder then bleed each wheel.

Thanks

Must be due to some quirk in the design or manufacture of the master cylinder - is it a generic rebuilt or parts-store replacement? I only deal with originals, and bench-bleeding isn't an issue with the originals.

:beer
 
Well I posed the question to Ecklers where I bought the cylinder from and they responded:

You can bleed the cylinder any way you want. The MFGR adds this disclaimer to cover their selves. Thank you. (that's a direct quote and spelling)

Anyway it seems I can bench bleed the cylinder......I hope so....don't understand the manufacture's warning however.

The cylinder itself should be an OEM replacement part from Ecklers.

Thanks Tom and JohnZ for your input.
 

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