Home stretch Master Cylinder check valve??

[g8rb8t]

Final steps of the Ch*vy disk conversion and I noticed in the two threads below the reference to a residual check valve to remove from the rear MC chamber. I used a #6 screw and turned 2-3 times and pulled but nothing is pulling out except the screw. Hopefully didn't screw up the MC.

How can I tell if I have this or not? Do all drum/drum MCs have this?

My MC was replaced by a shop about a year and a half ago. So close to being done!!

See final steps section in this link
http://earlybronco.com/Library/CustomFrontDiskBrakeConversion.pdf

http://classicbroncos.com/forums/showthread.php?t=139861&highlight=Residual+check+valve

 

[broncnaz]

Here this may help. I know its a j##p site but it has a good pic of what your looking for. http://www.jpmagazine.com/techartic...05_drum_to_disc_brake_swap_plus/photo_17.html

You either need a bigger screw or just turn it in farther before pulling the seat out. I dont think you'll screw it up and in any case its brass it should reform ok when you reinstal the steel brake line.
Its always possible that it doesnt have a residual valve already but you need to check.

 

[g8rb8t]

Thanks, that definitely helps. I'll give it another shot.

Is it possible to run drum brakes on a MC without a valve? Even if I don't have the valve should the brass seat come out?

 

[Apogee]

If it has a conical brass seat, then it will come out, generally without too much persuasion required. If it just has a machined cast iron or aluminum seats, whatever the body is made from, then obviously nothing is coming out. Instead of pulling the seats, you can also just use something small like a paperclip to see if there's anything behind the seat between it and the piston.

 

[g8rb8t]

Well, definitely see the brass. Guess I need a little longer screw because that thing is in there tight. I'll check paper clip too.

Any other tips?

 

[g8rb8t]

My best guess is its not there. I can put a 1 1/2" paper clip in and don't feel a thing. Man I hate not knowing for sure.

 

[Timmy390]

If you can put 1 1/2 paper clip in it and you hit bottom meaning you don't feel a spring then it's NOT in there. My new MC didn't have them and it was a drum/drum for a 74. Several people have noticed the rebuild ones form the local parts strores don't have them.

I used a punch to test mine. It hit bottom metal on metal so I knew it wasn't in there. The old MC had one. You could feel it with the punch meaning you could depress the spring. I popped the brass seat out and verified it was in there......

Tim

 

[g8rb8t]

Thanks Tim. MC was replaced about a year ago so Im gonna go with it.

 

[broncnaz]

The only time you really need a residual pressure valve is when the MC is below the rest of your brake system.

 

[g8rb8t]

Called the shop and emailed the MC manufacturer. He confirmed no residual pressure valve.

Glad to know for sure. Time to bleed!!