78 Brake Line Blocked
Thread Starter
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
78 Brake Line Blocked
Given it was 70 degrees today, decided it was time to start the refurb of my 78s brake system that would include replacement of calipers, hoses and master cylinder.
First was to clean out the brake lines with denatured alcohol. Gravity worked nicely on the front lines to drain both lines. Once I got to the rears, the right side rear would not drip. Went to the left side (drivers) and it drained as expected, emptying the M/C cylinder of denatured alcohol.
Went back to the right side and used a suction pump...and still would not pull fluid through the line. No wonder I had brake failure when I started this project.
Where's the blockage...proportioning valve? BTW, the caliper pistons had heavy corrosion built up within those cylinders. Thus the calipers became core exchanges.
First was to clean out the brake lines with denatured alcohol. Gravity worked nicely on the front lines to drain both lines. Once I got to the rears, the right side rear would not drip. Went to the left side (drivers) and it drained as expected, emptying the M/C cylinder of denatured alcohol.
Went back to the right side and used a suction pump...and still would not pull fluid through the line. No wonder I had brake failure when I started this project.
Where's the blockage...proportioning valve? BTW, the caliper pistons had heavy corrosion built up within those cylinders. Thus the calipers became core exchanges.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
You could take the bleeder screw all the way out. Spray some brake cleaner in the caliper threaded orfice and try again. I bet the blockage is right behind the bleed screw from corrosion.
Last edited by HeadsU.P.; Dec 24, 2017 at 09:14 AM.
Thread Starter
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
I should add, I cut the hose, bypassing the bleeder, the metal brake line with the bleeder and the junction where the line connects to the hose.
So bleeder blockage has been neutralized.
So bleeder blockage has been neutralized.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
So now, you have to back-track even further over to the junction fitting for the left rear caliper. That fitting might be the issue. You said left rear flows, right rear does not.
Always that chance that a brakeline was pinched from a floorjack or jackstands or something.
Always that chance that a brakeline was pinched from a floorjack or jackstands or something.
Thread Starter
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
After removing the cut rubber hose from the right rear block...gravity worked and denatured alcohol emptied from the M/C. So the blockage was in the host from the block.
I'll use air pressure to blow those lines out before reassembly of hoses and calipers.
I'll use air pressure to blow those lines out before reassembly of hoses and calipers.
