Master Cylinder Residual Valve

[FJROSS]

Yes, there is a top and bottom hole. I don't know what you mean by the "taps are in the center". Pictures might help.The bleeder is always at the very top because bubbles rise.

It sounds strange that you would have to turn them the opposite way that the manual says. Maybe you flopped them L to R? As long as you have tightened both adjusters so that the drum can't turn and the adjuster cant turn any more either, that is as tight as it gets. If you still have to double pump, something else is wrong.

These are the old wheel cylinders that came off the truck. I'm assuming that the threaded ports are in the center. Please explain the bleeders being to the top?

 

[FJROSS]

Heck. With all your "brake work experience" Dave, you must know a darn site more than me about this.

Perhaps all I can give you is moral support really. But I'll spew out a few more words........................... cos I'm always verbose.

The way I see it, regardless of what the "residual valves" and "proportioning valve" are supposed to do, provided they are full of fluid - how can they absorb "one-complete-pedal-movement's-volume-of-fluid" and thereby stop your brakes from being applied on the first pump? Surely they can't!

Which means - If you haven't got trapped air - You're back to questioning what's happening with every brake piston in your system. There must be one there that is travelling far more than necessary.

(Unless you have a brake line bulging out like a balloon which is a possibility that Pin_Head suggested.)

Your mission - To seek and destroy the culprit piston (Well. Maybe not "destroy" but it doesn't sound as good without that "destroy" bit.)

PS. It might be time for "desperate measures". Perhaps you could try isolating different wheels to see if the problem disappears. Say - Using vicegrips to "gently" clamp various hoses (but obviously you must be careful not to damage the hoses. And I probably shouldn't even be suggesting this.)

Thanks for the advice. I removed the rear brake lines off the tee fitting thats mounted on the axle and finally got a hard pedal. I lightly treaded the old brake bleeders into the tee to use as a plug. This at least rules out the front brakes and master cylinder out of the equation. My next step will be to install one side of the brake lines at a time and test as I'm going. This should hopefully find the problem side. Thanks

 

[lostmarbles]

In this thread here I posted photos of my rear backing plates and where the bleeders sit and how the lines are routed.

https://forum.ih8mud.com/40-55-series-tech/211355-brake-line-question.html


If that is any help.

 

[FJROSS]

PS. It might be time for "desperate measures". Perhaps you could try isolating different wheels to see if the problem disappears. Say - Using vicegrips to "gently" clamp various hoses (but obviously you must be careful not to damage the hoses. And I probably shouldn't even be suggesting this.)[/quote] This is how I isolated the rear drum brakes.

 

[lostmarbles]

Nice work Dave. And I see your problem in trying to achieve "bleed nipples on the top" (without balancing your cruiser on its nose or tail). Which is why I posted that link.

I tend to believe that opening a bleed nipple WIDE while someone depresses the brake pedal tends to create turbulence inside a wheel cylinder that drags a lot of trapped air bubbles out.

The only area that I've been unable to clear of air by that method is where my lines go up and over the back of my engine by the firewall (as I mentioned before). I've found that this area is too far from a bleed nipple. By the time I have to stop and refill my reservoir, that air is probably almost out. But of course stopping to refill the reservoir allows it sufficient time to travel back up and back to the same high point. (Well that what I think happens anyway.) So hence I back-flush that section if I know air has gotten in there.

Good luck with tracking it down and keep us posted as you "nail it".

 

[FJROSS]

Nice work Dave. And I see your problem in trying to achieve "bleed nipples on the top" (without balancing your cruiser on its nose or tail). Which is why I posted that link.

I tend to believe that opening a bleed nipple WIDE while someone depresses the brake pedal tends to create turbulence inside a wheel cylinder that drags a lot of trapped air bubbles out.

The only area that I've been unable to clear of air by that method is where my lines go up and over the back of my engine by the firewall (as I mentioned before). I've found that this area is too far from a bleed nipple. By the time I have to stop and refill my reservoir, that air is probably almost out. But of course stopping to refill the reservoir allows it sufficient time to travel back up and back to the same high point. (Well that what I think happens anyway.) So hence I back-flush that section if I know air has gotten in there.

Good luck with tracking it down and keep us posted as you "nail it".

I think I maybe destine for rear disc brakes. After getting a hard pedal with the rear tee plugged I started adding one side of the brake lines at a time to try and find the culprit. No luck, still had 2 pump pedal no matter which side I added. My next step was to remove the drums and install c clamps on all 4 wheel cyclinder to stop any throw and rule out the improper adjusted rear brake syndrome. STILL 2 PUMP PEDAL!!!!!. I've been using a pressurized tank that hold brake fluid that has a air blatter that lets you pressure bleed right into the bottom of the reservior cups, so that you dont need to refill the master as you would when you pump bleed. Also when I had the tee plugged I assume that if there was air in the high brake line behind the engine that I would have still had soft pedal with the rear tee plugged. The olny thing I can think of is there is air trapped in the rear ccot brake cylinders that I can't remove.

 

[lostmarbles]

Just one more thought - that's probably irrelevant Dave - But my master has a screw about half way down its length. To insert it correctly, I must have pushed my pistons all the way into my master cylinder BEFORE fitting the screw. (I use a phillips-type screwdriver to push them without risking damaging the bore.)

If I don't follow this procedure of pushing the pistons in first, then I will interfere with the correct movement of the pistons (when I push the brake pedal).

But I seem to remember the front chamber is for the front brakes so this is more than likely TOTALLY irrelevant.



Gotta dash off to work now. --- Probably shouldn't even have written this.

 

[65swb45]

I think I maybe destine for rear disc brakes. After getting a hard pedal with the rear tee plugged I started adding one side of the brake lines at a time to try and find the culprit. No luck, still had 2 pump pedal no matter which side I added. My next step was to remove the drums and install c clamps on all 4 wheel cyclinder to stop any throw and rule out the improper adjusted rear brake syndrome. STILL 2 PUMP PEDAL!!!!!. I've been using a pressurized tank that hold brake fluid that has a air blatter that lets you pressure bleed right into the bottom of the reservior cups, so that you dont need to refill the master as you would when you pump bleed. Also when I had the tee plugged I assume that if there was air in the high brake line behind the engine that I would have still had soft pedal with the rear tee plugged. The olny thing I can think of is there is air trapped in the rear ccot brake cylinders that I can't remove.

If you seriously think that trapped air in the rear cylinders is your culprit, try this.

With the shoes removed, pull the upper piston out of each cylinder, pop the upper cup, fill the cylinder manually, push the cup sideways below the surface of the fluid and rotate back into position. Voila, no more air!

Best

Mark A.

 

[Fast Eddy]

I think I maybe destine for rear disc brakes. ... STILL 2 PUMP PEDAL!!!!!.

I'm starting to think you got bad brand new cylinders. You wouldn't be the first. If there was some air in the cylinders I don't think you'd have 2 pumps, but instead 1 pump squishy.

Also, aren't the ports for the lines and the bleeders different? I thought they seated differently in the cylinders.

 

[lostmarbles]

But keep in mind that NOTHING can defy logic.

If "one-pedal-pump's-worth-of-fluid" is disappearing somewhere without the brakes being applied - Then it has to be going somewhere.

Or if that first pedal movement is not resulting in much fluid movement, perhaps there is a master cylinder fault. (- But this is unlikely if blocking off the rear brakes succeeded in giving a "hard pedal" following minimal pedal movement.)

When you take a lot of care to do something properly (as Dave obviously has done) then it's natural not to want to start questioning whether earlier work has been done right. But as an "old bastard", I've often experienced having to go back (and sometimes repeatedly too) over previous work to find the answer to my problems.

The people that fail (from my experience) are those that stop thinking logically (usually because they start thinking "it is all so mysterious and completely beyond me).

Hang in there Dave. When you find the answer you'll want to kick yourself because you'll probably see it's been staring you in the face all this time. (But that's life when you have hobbies like us!)

 

[FJROSS]

Once again, I would like to thank everyone for there help. The drums have just about got the best of me. The rig is drivable and from what I've heard from many others a common problem that people put up with. I think the last resort will be to try to bleed the cyclinders inplace like Mark A. has suggested. I will pop the top caps off and remove the rubber cup and submerge it sideways under the fluid and then try to seat it. Well.... it looks like it will work in theory. This is the only place that i can think that air may still be trapped. I will keep you all posted. Thanks Dave

 

[FJROSS]

I'm starting to think you got bad brand new cylinders. You wouldn't be the first. If there was some air in the cylinders I don't think you'd have 2 pumps, but instead 1 pump squishy.

Also, aren't the ports for the lines and the bleeders different? I thought they seated differently in the cylinders.

Yes the bleeder threads and seats are different and need to be lighly threaded into the tee. I was very cautious in doing this not to bugger up the threads on the tee.

 

[lostmarbles]

One more "brain storming type" reply.

How well do your shoes fit your drums Dave? I mean - Are they new shoes that are "radius ground/sanded" to match your drums? Perhaps poorly matched shoes could be your problem?

I just thought of this because I remember what happened to me. I had been having trouble with excessive pedal travel and brake unevenness (discrepancies between right and left braking on an axle that showed up on specialised WOF braking performance tests). There still looked to be a lot of "meat" on the shoes so I was reluctant to replace them. Yet replacing them had an amazing effect. The brakes became so much easier to set-up. And I took the cause to be the better "radius fit" of new shoes compared to the old. (After all, it is the leading edges of the shoes that cop the wear.)

 

[albee]

If you seriously think that trapped air in the rear cylinders is your culprit, try this.

With the shoes removed, pull the upper piston out of each cylinder, pop the upper cup, fill the cylinder manually, push the cup sideways below the surface of the fluid and rotate back into position. Voila, no more air!

Best

Mark A.

This is the just about the best advice, that I have read on IH8MUD. I always read his post knowing that the advice he gives is always thoughtful, and spot on.

Thanks Mark