rear brakes not releasing

[resq302]

Ok, I just got the charger fixed from the issue with the rear end problem.  Now after the second drive after the break in of the rear, I developed a new problem.  My rear brakes are not releasing.  It is not just one side, it is both sides!  I replaced all of the rubber and steel lines last year and have had no problem with the system after I did that.  I pressure bled the brakes and used all new DOT 3 brake fluid.  I removed the rear drums and pressed on the brakes and the shoes expanded when I pressed on the brake pedal but when I let off the brake pedal, the pedal went up but the shoes did not return to the normal resting state.  I am in the process of getting ready to put a reman'd 1969 correct power disc brake master cyl back onto the car as I think it might be the problem.  The front disc brakes are releasing like normal and are not hanging up at all.

Can anyone post some suggestions as to what might be causing this problem in my 69 Charger?  I would like to get it back together and get some more mileage on it to make sure the rear is set up correctly before the snow starts to fly.  Any suggestions is greatly welcomed.  My theory is that something inside the master cylinder is not pulling the fluid back into the reservoir for the drum part of the brakes since the front disc brakes are working like normal.

The current master cylinder I have on the car is a 1971 disc brake master cyl if it matters.  I have a correct 1968-1969 disc brake mastel cylinder ready to install.  Just waiting for the semi gloss black paint to dry on it.

Thanks for any suggestions.

Brian

[resq302]

anyone?

[Plumcrazy]

The return springs are what pushes the fluid back into the master cylinder.  I would start at the rear brake hose and loosen the brake line connection and see if the brakes release.
If they do start working your way forward until you find what is stopping the fluid from going back into the master cylinder.

[resq302]

Thats actually a good idea.  I never would have thought of that.  I was always under the impression it was a suction action that was pulling the fluid back into the master cylinder.  I did crack the fitting at the rear flex hose and that made the shoes go back to the resting state.  I will have to try that idea of pressing the pedal down and then cracking the line at various places to see.

[Chryco Psycho]

you could get a new set of springs $20 will get a whloe new set for both sides

[resq302]

I just installed all new brake hardware last year when I rebuilt the entire rear.  At that time I put in new wheel cylinders, brake hardware, new shoes, and new drums.

[BrianShaughnessy]

Theory 1.    Adjustable pushrod for the MC is too long.
Theory 2.    Check the parking brake adjustment and / or  corroded, sticking cables .   

[resq302]

Brian,

Regarding your first theory.... master cyl. push rod was never touched as the master cylinder has not been replaced yet.

Second theory : parking brake was not adjusted lately as when I crack the bleeder screw on the wheel cylinders, both shoes return to normal rest locations.  So I doubt the parking brake adjustment or cables is the issue.

It is almost like something is blocking the flow of the fluid going back into the reservoir.  I will have to check the holes in the bottom of the reservoir tomorrow when I am off to see if any of them are blocked.

[BrianShaughnessy]

   
OK.. that was my list of usual suspects - even if the MC pushrod symptoms normally show up as dragging front brakes.   I didn't see the results of your bleeding test - thanks for the update.

Check your flexible hose to the rear end.     A common but difficult diagnosis of front brakes on 3rd gen F bodies is a brake hose that has internally corroded and collapsed to the point that it's a one way valve that lets pressue thru to apply the brakes but doesn't allow return.     Sounds like a similar situation.   

[resq302]

Brian,

This is is a second gen charger. 
Rear flex line was recently replaced also with no change.  That was my first thought also but no success.

I have heard it could be the master cyl as sometimes the rubber cups could fold over when it is retracting and not causing a suction to pull the fluid back somewhat.  I'm kind of hoping it is that so it is a somewhat simple fix.

[BrianShaughnessy]

I'm well aware it's a 69 Charger but you you didn't mention changing the  flex hose previously either.   Oh well.   

[resq302]

Ok, I just got the charger fixed from the issue with the rear end problem.  Now after the second drive after the break in of the rear, I developed a new problem.  My rear brakes are not releasing.  It is not just one side, it is both sides!  I replaced all of the rubber and steel lines last year and have had no problem with the system after I did that.  I pressure bled the brakes and used all new DOT 3 brake fluid.  I removed the rear drums and pressed on the brakes and the shoes expanded when I pressed on the brake pedal but when I let off the brake pedal, the pedal went up but the shoes did not return to the normal resting state.  I am in the process of getting ready to put a reman'd 1969 correct power disc brake master cyl back onto the car as I think it might be the problem.  The front disc brakes are releasing like normal and are not hanging up at all.

[is_it_EVER_done?]

Sounds like a bad residual pressure valve in the MC outlet to the rear brakes. Do the brakes release if you loosen the brake line for the rear at the MC? If so, pull the residual pressure valve and try it without it, or replace it with a new one.

[resq302]

Is it ever done,

How do you get the residual pressure valve out from inside the master cyl?  Just curious as I will be replacing the master cylinder with the correct appearance one from 1968-1969.

Brian

[resq302]

UPDATE!!!!

Well I tried the method of cracking the lines till I located an area where no brake fluid was coming out under pressure.  It seems to be the proportioning (hold off) valve that is in the front to rear brake line and is mounted on the frame rail under the floor board.  The line going into it would drip while the line coming out would spray out the brake fluid.  I called In Line Tube and they said to send it back and they will check it out as I only purchased it this past March and installed it in May.  They said it might take a couple of days for them to check it out as they have some work pending also.  This piece was a new reproduced item they started making.  Hopefully they will make good on it if it is stuck or not working right.

[Shakey]

UPDATE!!!!

Well I tried the method of cracking the lines till I located an area where no brake fluid was coming out under pressure.  It seems to be the proportioning (hold off) valve that is in the front to rear brake line and is mounted on the frame rail under the floor board.  The line going into it would drip while the line coming out would spray out the brake fluid.  I called In Line Tube and they said to send it back and they will check it out as I only purchased it this past March and installed it in May.  They said it might take a couple of days for them to check it out as they have some work pending also.  This piece was a new reproduced item they started making.  Hopefully they will make good on it if it is stuck or not working right.

Can please post a photo of this valve Brian?

[resq302]

Mike,

That valve is the one that looks like a brass T that is under the driver side floor board.  I will try and get a photo for you today.

Brian

[resq302]

pic of prop valve

[Shakey]

I didn't realize anyone was reproducing those valves.

Can I ask how much it cost you to purchase it?  How about the metering valve, the one in front with all of the lines going into it and the wire for the light on the dash - are they making those also?

[resq302]

They are reproducing the proportioning valve but they call it a hold off valve.  I do not know about the distribution/metering block as I was able to use my original one that I had rebuilt a couple years ago due to the light coming on inside the dash.  The proportioning valve cost me $84 at the time and they have since dropped the price to $74.  The piece is all new brass that is machined and smoother in appearance than the originals but aside from the slight appearance difference, it is a dead on match.   You can try to call them to see if they are making a new metering/distribution block.  Their web site is www.inlinetube.com.  All of their other stuff is overpriced compared to The Right Stuff who also makes fuel and brake lines with the correct bends, but this was the only place that I was aware of that was reproing the valves.

[Steve P.]

Another thing to try when in doubt about your peddle rod length is to back off the bolts that hold your master to the firewall. If you back off the bolts and your shoes return to their seat your rod is too long.

Some have tried to mount the master without the stiffening plate and this is what they end up with..

[resq302]

Steve, there is no doubt that the pedal rod length was not the problem.  The system worked fine up until I took it out for the break in after I had the rear axle problem.  If the pedal rod was touched, I could see that being a possibility, but since it worked fine before, I highly doubt that it would be it.  Also, I found out that the proportioning valve show in the picture above was not letting the fluid back through and acting as a one way valve.

[Steve P.]

I did see that you thought you had found the problem with the prop. valve. I added the stiffening plate/rod length issue for others who are also reading about this problem.

Sorry for the confusion..

[resq302]

no prob.