camaro brakes

[onebad34]

Having trouble getting breaks on this 67 camaro. Got the back to bleed, but cannot get the front disc to bleed.  Have tried pumping also using a vacum pump. I read in the book that when bleeding,  the pressure valve directly under the master cylinder , you should depress the back side. Mine will not move. I noticied the intake side is wet, but the outlet is dry. I even attempted to apply air to see it will open. I was up to 80 psi and nothing.  What is the proper way to test and at what pressure?  Also, I bought a correct rebuilt "WT" code master cylinder. being my car is disc/drum, should there be check valves in the master cylinder and if so, on which end, front or back, or both.  Any help will be appreciated.  Pete

[JohnZ]

If that valve is stuck, you also won't have any front brakes - was that the case before you started bleeding the brakes? A correctly-built replacement disc/drum master cylinder has a residual pressure valve behind the brass tube seat in the rear outlet port, and none in the front port.

[onebad34]

John, This is a camaro my son and I are restoring. We are at the brake issue, then front end alignment, then the front walk away.  These are all new parts.  The master cylinder was purchased from  Heartbeat City and the Pressure valve from The Riight Stuff.  Question is How is the pressure valve suppose to work and at what pressure should it open.  By the way, the master cylinder does not appear  to have a check valve on either end. 

[Steve68]

Pete

You might want to review this thread for some info on "RPV" that John refers to in his thread.
http://www.camaros.org/forum/index.php?topic=2938.msg18849#msg18849

Steve

[JohnZ]

Question is How is the pressure valve suppose to work and at what pressure should it open.  By the way, the master cylinder does not appear  to have a check valve on either end. 

The metering or hold-off valve is designed to open (to permit fluid flow to the front system) when it sees 30-40 psi. You can check for presence of an RPV by gently using the blunt end of a drill bit as described in the archive link in the post above.

[motion427]

as a professional brake technition, i suggest you loosen the master cylinder from the booster. open only the rear bleeders and as soon as you get fluid close them off. Then go to the front and do the same. MAKE SURE that all 4 wheels have gravity bled with the master loosed away from the booster, and also do not put the master cap on as it will bleed faster with it off. now once you have made all four wheels drip, tighten the master back to the booster. NOW recheck the bleeding at the wheels, reopen the rear and make sure they still drip, then reopen the front and make sure they also drip. If none of them do you want to check the rod that goes into the master from the booster for proper length!! if it moves those internal pistons at all it can block the comp ports and you will never bleed it. try this and let me know!!

[onebad34]

Thanks for the reply. Here is where I am now.  First, this is the second mc . the first one leaked out the back spool and ran down the booster. It had a check valve in both ends. If I understand correctly, being a disc/drum car, only the back one should have the check valve.  Now the second one, also a WT code for the 67 camaro does not leak, but has no check valves on either end. Will call heartbeat tomorrow. I believe these were the only two WT code they had. I have attempted to gravity bleed, pump pedal, and vacuum bleed this car. The back bled well, I cannot get any fluid out the front, which are also $600 original/rebuilt calipers with the 2 piece rotors. What I have learned but don't understand is the round valve under the master cylinder, which is also new. The manual says to push the back of this valve to release while bleeding. Mine won't move, the rod only spins. I did notice the intake side was wet with fluid, and the output side was bone dry. I attempted to blow air through and went up to 100 psi in 10 psi graduates with the valve never letting any air through.  The complete break system on this car is new or expensivly rebuilt.  JUST DON'T WORK.   Any advice will be appreciated.  Pete  One more thing, I backed off the adjustment rod inside the car from the booster to the pedal, I adjusted till I have appox 1/4" travel before moving spools in MC.  Pete

[onebad34]

Back again, No breaks yet.  Contacted Heartbeat City, They will not put the check valve in the MC stating liability issue. Advised the manual calls for a check valve in the MC on the back for the rear drum breaks.  They gave us the option to send back for refund. Problem is to do the car right, need the WT code MC.  What do I do.  I ordered a MC rebuild kit, only way to get the check valves.  Opinions on what to do.  Keep MC and put in the valve myself or disreguard?  Question:  I understand you use a fitting to press in the new valve and brass fitting.  What is to correct way to get the old one out without damaging the MC.  I also temporally eleminated the round pressure valve under the MC and now get fluid to the calipers. Still does not appear to build pressure. With the vacuum pump, I keep getting air.  I have gone over ALL the fittings and they are tight.  Is there an issue with stroke?  where else could I be getting all the air.   Any help appreicated   Pete

[SS375HP]

We have had a very similar brake situation which nearly got the best of us. We too had trouble getting the front discs to bleed and work properly. Just as "Motion 427" stated above, check the rod between the power booster and the master cylinder. We found that the rod didn't fully seat into the back of the master cylinder piston. The end of the rod is "ball" shaped. The machined surface of the back of the piston was "coned" shape. Because the "ball" end would not go all of the way into the "cone" effectively the rod was to long. With the rod to long apparently the piston couldn't come all the way back to allow the cylinder to reload and push the fluid to the front brakes. I really didn't want to beleive this was the problem, but after getting the end of the rod to fully seat into the piston, we were able to bleed the brakes. Perhaps this condition exists now because of the many different vendors who re-build or re-manufacture the master cylinders. This may not be your problem, but speaking from recent experience you might want to check it out.

Also there were two lengths of the rods. We had the 'short one". It sticks out of the booster about 1/2 inch. The longer rod sticks out about 1 1/2 inch. First check to be certain you have the right rod. Use the short rod if the master cylinder piston is about flush with the back. If the piston is recessed an inch or so you'll need the longer rod. Because you are using new parts not previously working together the booster rebuilder probably provided a rod without knowing how it would work with the master cylinder.

The brake system is really pretty basic, but can drive you crazy when you are working parts from so many differnt sources.

Good Luck,

Please let us know when you get it working... by the way you will get it working sooner or later.

[Steve68]

Pete

Code: [Select]

What is to correct way to get the old one out without damaging the MC.Start here http://www.camaros.org/forum/index.php?topic=2938.msg19259#msg19259 and follow the next 7 or so pictures with instructions.

Steve