Postby Tramp » Fri Aug 17, 2007 1:02 pm
Wow is right. Wonderful work, Andre.
What Mitch wrote in my PM was so informative I am placing it here:
"Well, Tramp, here's the long and the short of it.
1. When you remove the cover of the master cylinder, is it a single large chamber or does it have 2 chambers? If single chambered, that means all 4 wheels feed at the same time. If dual chambered, (small in front, large in rear), then it is a split system. The small chamber in front is actually the rear brakes, and the larger chamber in the rear is the front brakes. Which one is empty? If the front one is empty, then we know the leak is somewhere in the rear brake system. Rear one empty, the leak is in the front brake system. Diagonally split brake systems didn't show up 'til the '80s.
2. If you have a single master cylinder chamber, then the leak could be anywhere. A single cylinder master cylinder will have only 1 line (usually has a couple coils in it), that comes off and goes to a brass splitter block. 3 lines will come from the splitter. 1 short line going to left front, 1 long line going to right front, and 1 long line going to the rear. The line going to the rear will usually end at a crossmember, or even mounted directly to the left frame rail. From there, it will have a rubber brake hose that will reach down to a splitter block on the differential housing or somewhere on the rear axle. From that splitter, 1 line to the left rear wheel cylinder, 1 line to the right rear cylinder. That line could be rusted away anywhere along its' length along the left frame rail, behind a shock mount, or behind the gas tank. The lines on the rear end housing are easier to see, and they could have a rust hole in them also.
Back up to the front, the line to the right front wheel could have 3 directions of travel. It could leave the splitter and be fastened to the firewall, curve up and over the tranny tunnel, and back around to a bracket on the frame side by the upper control arm. Or, it could go across the front crossmember either in the front or back, or it could go all the way to the front yoke and around to the right frame rail. The bracket holds the hose to the right front wheel cylinder or caliper, if you have front discs. Generally, these rust away pretty close to the hose bracket. Left side pretty much the same, only that line is very short, sometimes only 8" to 12" long. If the line is on the crossmember, sometimes leaking oil and grease buildup can hide the leak.
Of course, any of the 3 hoses could be blown out, but with that big of a leak, the pedal would go right to the floor probably on the first pump.
Andres' suggestion to look for a telltale fluid streak going down between the master cylinder and the brake booster is a good one. Of course, if the Chevy don't have power brakes, as many didn't until the very late sixties, that point would be moot. A leak in the master cylinder itself would manifest itself as a slowly dropping pedal while you're already stopped, and then you'd leave off and get another bite and it would hold mometarily. A blown line or hose will have a dropping pedal under both conditions.
Get 'er up on jack stands, fill the master cylinder with brake fluid, and get somebody to pump the brakes and you go lookin' with a flash light for the telltale squirt. Let's face it, pal, the old girl's 41 years old. It certainly wouldn't hurt to rebuild the entire brake system, and probably not that expensive either. If you're in over your head on making up and flaring new steel lines, then have it done at a reputable shop.
The 2 systems on the car that can kill you, (and possibly someone else), are the brake system and the exhaust system. I don't care if the transmission falls out and skids across the road, I want to get the damned thing stopped."
Now to clear up a few things. My '66 does have a dual-chamber master cylinder, but I installed it. Both chambers are the same size and only the rear one which feeds the rear drums is leaking. It only loses about half a chamber in two or three weeks. The car does have vacuum assisted brakes. Why the hell do they fashion brake lines out of a corrosive material?
That a life will be spent gaining inches,
When this distance is read in miles.