Wilwood master cyclinder

[DButler]

I am currently installing a Wilwood 1" bore master cylinder on my 67 Camaro. I had power brakes on the car and I have switched over to manual. I have my original manual pushrod and it feels like the rod is touching the piston when you get under the dash and try to adjust it, but when I go to bleed the brakes and puch the pedal down it goes to the floor like it has no pressure. I open the master cylinder lid and it is still full of fluid. When I disassembled the brakes I blew out the rear brake lines with air to clean them out so they are completly empty. Any ideas as to what is wrong. The master cylinder is new and bench bled fine. I am assuming its the rod but I am not sure. I have the rod mounted in the top hole on the pedal which is a 6:1 ratio. Any help is greatly appreciated. Thanks

[Apogee]

You won't generate any pressure at the master cylinder until the system is full of fluid. Right now, you're probably just compressing the air in the system and nothing is moving. Assuming you have already fully bench bleed the MC (did you confirm that it was fully bench bleed?), the next step is to fill the system with fluid. If you've got time, gravity bleeding has worked well for me in the past and is by far the easiest method requiring the least effort and/or tools. For quicker results, a vacuum bleeder at the calipers can be used as can a pressure bleeder from the MC side. I've seen a few tools that allow you to fill from the calipers up (like most hydraulic mountain bike brakes really), but now you're getting outside most people's comfort zones.

All that said, once you have mostly brake fluid in your system versus mostly air, your pedal should firm up and you should be able to bleed your brakes however you would normally.

Tobin
KORE3

[DButler]

Ok ill gravity bleed today. I bench bled it and the lines where full of fluid with no air in them so I am sure it was bench bled correctly. I think you are right that it is just full of air. Because I checked the rod in the master cylinder before I installed it and the rod boot is in the same position so im pretty sure the rod is touching. Do you know if the stock manual rod is usually long enough or does most people have to add to it? It feels like it is touching. So you think the reason the fluid level is the same in the master cylinder and nothing has pushed in the lines because it is full of air? Once it gravity bleeds and I get some fluid at the calipers I sound have somewhat of a pedal right?

[DButler]

If I have fluid at the calipers after gravity bleeding and I still do not have a pedal then it has to be the rod length right?

[Apogee]

...I bench bled it and the lines where full of fluid with no air in them so I am sure it was bench bled correctly...

To be 100% sure your MC is fully bleed, plug both (or all four in the case of the Wilwood universal tandem MC) and stroke the piston. It should hydraulically lock after about 1/8" of piston travel. If it's spongy, then it still has air in it.

Tobin
KORE3

[Apogee]

If I have fluid at the calipers after gravity bleeding and I still do not have a pedal then it has to be the rod length right?

That would depend on what symptoms you may or may not still be having. Pedal pushrod length shouldn't have any bearing on how "spongy" the pedal is, only whether the pushrod allows the piston to fully retract upon release (thus allowing fluid to return from the calipers back to the MC) and where the pedal comes into contact with the MC relative to its stroke. Too much free play and you may not have enough stroke to achieve lockup before bottoming out the pedal.

Tobin
KORE3

[DButler]

Sorry for all the questions, but I knew with brakes and I am trying to learn the in and outs. So when I plug off all sides then i should be able to touch the pedal and it should lock immediately, if not then I need to start by bench bleeding the mc again then go to gravity bleeding right?

[Apogee]

That would be correct. By plugging the master cylinder outlet ports, you remove all of the hard lines and calipers from the equation so you can verify whether the MC has been fully bleed or not. If you're testing the MC on the bench, then the stroke should be about 1/8" give or take before it hydraulically locks. If you're doing it in the car, your stroke should be 1/8" multiplied by your pedal ratio (6), so about 3/4" at the pedal.

If you do need to rebleed the MC, you can do it with the outlet ports plugged in a vice. Angle the nose of the MC downward slightly and tap on the body of the MC with a soft mallet or deadblow hammer while slowly stroking the piston assembly. You should see air bubbles come out of the compensator ports inside the fluid reservoirs.

Hope that helps and have a good holiday weekend.

[woody80z28]

That would be correct. By plugging the master cylinder outlet ports, you remove all of the hard lines and calipers from the equation so you can verify whether the MC has been fully bleed or not. If you're testing the MC on the bench, then the stroke should be about 1/8" give or take before it hydraulically locks. If you're doing it in the car, your stroke should be 1/8" multiplied by your pedal ratio (6), so about 3/4" at the pedal.

If you do need to rebleed the MC, you can do it with the outlet ports plugged in a vice. Angle the nose of the MC downward slightly and tap on the body of the MC with a soft mallet or deadblow hammer while slowly stroking the piston assembly. You should see air bubbles come out of the compensator ports inside the fluid reservoirs.

Hope that helps and have a good holiday weekend.

Must be pointing the nose down helps release the trapped bubbles? I will try this with mine. Thanks