Pressure Valves

[Tman 1957]

Morning all here is the deal im having a big problem with a rock hard brake pedal tried new master oh and yes it is 4 wheel drum the pedal will not bleed like normal two feet on pedal pushing really hard and barely getting a dribble out of bleeders could it be that the residual pressure vales are screwed up ??? also after bleeding everything still have hard pedal and no brakes brakes are adjusted right to almost dragging on drum. just dont get it ..

 

[Ma_n_Pa T]

Tman, if you have RPV in the system, you must have them in the right way, they only work in one direction, sounds like they are installed backwards, to check them, undo the fitting on the wheel side of the valve and push on the pedal, if no fluid the RPV must be turned around. Most of them are marked with an arrow or dot on the end that goes towards the wheels. Just my personal thoughts I dont like them and dont use them in my system at all, I have not had any problems without them.
Jerry

 

[Tman 1957]

Tman, if you have RPV in the system, you must have them in the right way, they only work in one direction, sounds like they are installed backwards, to check them, undo the fitting on the wheel side of the valve and push on the pedal, if no fluid the RPV must be turned around. Most of them are marked with an arrow or dot on the end that goes towards the wheels. Just my personal thoughts I dont like them and dont use them in my system at all, I have not had any problems without them.
Jerry

Thanks Jerry I will check when i get home from work today, thinking about taking them out of the system all together

 

[T-Test]

You could have a M/C with the residuals in it, and adding the second set making it act like this.

 

[Tman 1957]

You could have a M/C with the residuals in it, and adding the second set making it act like this.

Hear is the latest and greatest, went home last night and drilled out pressure valves have a pedal that feels spongy and does not put enough pressure on wheels with someone stepping on pedal i can still move tire with little or no resistance WTF this is starting to get old now im starting to thing back to the slaves and replacing them and see what happens...

 

[Tman 1957]

And the brakes are adjusted to almost rubbing on drums

 

[Ma_n_Pa T]

And the brakes are adjusted to almost rubbing on drums

Ok it sounds like you had a hard pedal before you drilled the PRV’s out so they must have been in backwards.
Let’s go over this a bit,
Hard pedal= blocked system, frozen slaves or calipers, RPV’s installed backwards. RPV’s in the masters are little rubber duck bill valves, RPV’s in the system keeps pressure on the slaves or calipers, that said I personally do not like any RPV’s in the system and I would remove them as well but that should not be giving you a soft pedal.
Soft or spongy pedal= Air in the system or leaks, MC not bench bleed (air in the master, lines or calipers/slaves)
You say now the brakes have a spongy pedal, that sounds like air in the lines to me, if the slaves were froze up and not moving I would think the pedal would still be hard. You never said, since you removed the RPV’s, are you getting good fluid to the wheels, does the pedal drop to the floor when bleeding?
Some systems are a bear to get all the air bleed out, don’t give up, spend more time bleeding the system, you had a supper hard pedal when the RPV’s were in backwards so the master sounds to be bleed enough with no air in it. Keep bleeding the system you will get it, If you get back to having a hard pedal and still don’t have good brakes then look at replacing the wheel slaves. I have seen some people had to jack the front/rear end up high to get all the air out of the system, that may help in getting all the air out.
Jerry

 

[Flatsman]

I assume that you have a dual MC. How old is it and are you having a hard time with all four wheels or just the front or back wheels. Is this a new build or has this been driving OK in the past? I see that your MC is new and assume that it was replaced because of your current problem.

 

[Tman 1957]

I assume that you have a dual MC. How old is it and are you having a hard time with all four wheels or just the front or back wheels. Is this a new build or has this been driving OK in the past? I see that your MC is new and assume that it was replaced because of your current problem.

Yes it is new and not sure of history?? I drilled out pressure valves and am putting new slaves in .They look a little shitty, and see what that does...

 

[Flatsman]

The reason I asked all those questions is that I just went through the same symptoms on a dual master cylinder. We could not bleed the back right rear brake and could barely bleed the left rear. We replace the master cylinder and everything returned to normal. I have seen new master cylinders that were bad so just something to think about. Good luck!

 

[Ma_n_Pa T]

So what did you find Tman, did you get it fixed?