Cascade Crew

Al Hasse · Posted: Sun Jul 20, 2008 4:52 pm Post subject: adjustable prop valve question

After finishing up my brakes and getting what I thought was all the air out, my pedal was still a bit spongy. I had the valve set to 1/2 per the directions, but haven't yet had time to go and test the brakes at lock-up (I want a few miles on them first). Yesterday, out of curiosity, I added one turn more toward the rear and the pedal firmed up considerably. I didn't think that was supposed to happen, do I have a prop valve that's not working as it should?

blue89 · Posted: Sun Jul 20, 2008 7:35 pm Post subject:

Mine was pretty hard to bleed out. You may want to try bleeding it out all the way open. What master cylinder are you using? I would think you would have a lot of pedel travel with the stock unit and those larger cylinders.

Al Hasse · Posted: Sun Jul 20, 2008 7:48 pm Post subject:

I have the stock master cylinder on there for now. I took apart the 4th gen one I had problems with and cleaned it out as much as possible - it was pretty gunky inside, and it still needs a reservoir.

When I bled it out, I couldn't get much fluid to flow out of the rears unless I opened the prop valve all the way (counterclockwise) - I gravity bled the system, the 4th gen master wouldn't gravity bleed for the front, no flow whatsoever, but I got fluid out with a helper on the pedal.

The knob on the prop valve seems to be labeled backward as decrease is counterclockwise and seems to open the valve so I can get fluid to flow to the back when I gravity bleed the rear.

blue89 · Posted: Sun Jul 20, 2008 8:20 pm Post subject:

I'm not sure how the are plumbed inside. I guess you won't know if its plumbed backwards until you go out for a lockup test! Very Happy

I had fun setting mine up.

iansane · Posted: Mon Jul 21, 2008 7:49 am Post subject:

Al Hasse · Posted: Mon Jul 21, 2008 9:59 am Post subject:

blue89 · Posted: Mon Jul 21, 2008 11:50 am Post subject:

Without looking, I think clockwise increases the amount of pressure that gets to the rear, counterclockwise decreases it. I have no idea how it works inside though. I could only speculate that to provide fluid flow as well as stop pressure that there must be some sort of spring bypass valve. Maybe to bleed the rear you need to push the brakes really slow as to not move the internals of the valve? I can't seem to find anything online about it. I must have done something right when i bleed mine Laughing

Al Hasse · Posted: Tue Jul 22, 2008 12:26 pm Post subject:

Well then it stands to reason that I still have a little air in the lines to the rear. By turning the bias to the left and decreasing rear bias, the pedal firms up a little.

I cleaned up my 4th gen master cylinder yesterday and there was lots of gunk inside, maybe the piston was hung up in the bore, and maybe there was my excess pressure issue??? I'm going to try and put that back on this weekend.

blue89 · Posted: Tue Jul 22, 2008 12:42 pm Post subject:

Makes sense to me. Pinch off the lines that have the air in them and the pedal gets better.

Are you going to try to bench bleed the MC? I still have made no progress on my swap. I'm waiting for a 1/2" drill from my friend.

Al Hasse · Posted: Tue Jul 22, 2008 1:38 pm Post subject:

I don't think there's any better way but to bench bleed. No special tools required, just fittings and lines routed back to the reservoir.

I pocketed a pushrod out of a 4th gen booster today at the JY, just for comparison with the 3rd gen pushrod. There is a significant difference in length, but most likely due to a difference in depth between the two boosters. The 3rd gen rod also has what amounts to a rubber spacer on the end that's about 1/4" thick. Any ideas what that's for?

blue89 · Posted: Tue Jul 22, 2008 1:53 pm Post subject:

I'm not sure what thats about. I'm pretty sure I kept the pushrods with their MC. I still have the 4th gen booster at home. I'll see whats left on it when i get home.