Good evening experts,

I recently rebuilt the calipers on my '69 Coupe, replaced all four hoses, the front crossover, the left line that connects from the proportioning valve to the front left caliper and both back caliper to hose lines.

When I bled the back brakes, I had absolutely no problem.  Pressure in the vacuum built up very easily and the fluid drained as expected.

However, when I moved to the front calipers I couldn't build up pressure in the vacuum and I got no fluid run out. 

After inspecting the MC I found that the little valve looked a bit corroded (couldn't see the piston moving the same as I could in the well for the back brakes), so I drained the front well and cleaned it up with a shop towel and a toothbrush (and a toothpick).

It made no difference. 

Frustrated, I disconnected the line from the proportioning valve and tried to bleed from there.  Nothing.  Pumping the petal would give me a small burst of fluid, though.

So, I disconnected the line that runs from the MC to the Prop. Valve, and I had minor fluid run out.  Nothing that would compare to the fluid running out of the back well when disconnecting that line.

The same went for the left front side.  Depressing the pedal would give a squirt, but nothing more. 

I connected the battery back (I'm redoing the wiring in the cab) and checked the brake light in the back--thinking that maybe it was the Prop. Valve--but that worked as it should.

This only leaves me to believe that I've got a MC problem, but if I disconnect the MC to PV line, I can drain the fluid in the front well using the vacuum bleeder, so I know that the fluid is running from the MC front well to the line... but not near with the same flow as the rear well.

I'm stumped.  Also, this is my first Vette, so talk down to me, otherwise I'm going to be a bit confused.

Thanks guys,

Kelso

Rebuild or replace the master cylinder. Sucking the fluid out with a vacuum pump is not the same as using the piston in the mc to pump the fluid. You may be able to remove any air out of it, but it still needs to be able to pump pressure. Sounds like the seals are bad on the piston to me.

Sigh.  I was afraid that would be the answer.

Does the AIM cover the relative information required for me to rebuild, or is there a special manual/diagram/procedure I should follow?

If the AIM covers the MC in enough depth for me to rebuild then no worries--but as mine is 35 miles away on the rear-end of my car, I'm unable to reference it.

I'll do a quick search here and see if I can come up with something.

Thanks AA,

Kelso

The AIM will do you no good in regards to rebuilding the MC. The Service Manual will, tho, if you have one.
They are not that hard to do, but...if there is any corrosion on the inside of the cylinder, it would not be advisable to do it. They can be bored/sleeved if corroded, but that ain't cheap. Like Ron, I would say get a reman, or "new", and install for now. If you later want to have the original MC back on the car, you can have it repaired then.

A little info if you do get a reman...check the depth of the hole/seat in the piston that the pedal rod fits into. There are at least two different depths on these MC pistons. Neither will interchange. This is the seat(piston) that the rod from the pedal, or the booster, if you have power brakes fits into on the MC.

If you have a deep-hole car, and put a shallow MC on, the pedal won't move the piston in the MC.
If you have a shallow hole car, and try to install a deep-hole MC, it won't bolt up fully.
Hope this hasn't confused you...

I went ahead and disassembled the MC this morning and the rear piston was badly corroded.

I went to AutoZone to see if they had any rebuild kits, and they did, but they had a reman for only 17$ with a 12$ core charge.  So I bought that one and took her home and slapped it on. 

After the bench bleed and the re-bleed on the calipers, I now have functioning brakes with a firm pedal.  I'm going to monitor it over the next week or so to make sure there aren't any leaks and that the pedal stays firm.

Unfortunately, when we put the wheels back on and took her off the jack stands we found a problem with the transmission and/or shifter... we have two gears we can shift to... 3rd and 4th.

When we throw it in neutral, we can't roll the car, and I can't get the ignition to go to lock to withdraw the key, which at first made me think I needed to check the lever.. but now we think it is stuck in 3rd gear and not shifting out..

So, next weekend is going to be a blast when I have to re-jack it and drop the transmission! *grin*

Thanks for the help all,

Kelso

Don't go droppin the trans just yet...
Sounds more like one of the linkage rods has come undone from either the shifter, or the trans.(sound familiar, Dwain?)I would suggest you jack it up, and look for a linkage that has come off. If it came off while it was in one of the gears, that would explain why you can't roll it. If you can put it into 3rd or 4th, put it in one of those gears, and see if the car moves, or if it binds up(engine running, and let the clutch out...). If it binds up, and won't move, then it is probably a linkage arm that has fallen off. What is happening is you're attempting to put the trans in two gears at once, which will bind it.
If you put the shifter in the neutral position, and let the clutch out, it should try to move forward or backwards. If it moves forward, the trans is in 1st or 2nd. If it moves rearward, the trans is in reverse.

                                                         Click for larger image
                                                       (reverse linkage is to the right, just outside of photo)Adams' Apple2007-08-19 18:49:33

I'll most definitely look into that Joel.  Thanks for all the help and advice.