Brake Problem Questions

[Robert Crandall]

I had a problem with a front caliper locking. I searched this forum and was happy to find my answer here:

http://67-72chevytrucks.com/vboard/s...d.php?t=752778

As recommended on that thread, loosening the bleeder screw unlocked the caliper, which identified a clogged flexible brake line, so I replaced both of the front flexible lines.

I still have a problem, so I started this new thread.

I had a very difficult time getting to the connection of the steel brake lines to the flexible ones inside the frame channel. I could not get the passenger side one to stop leaking with no pressure other than the weight of the fluid, but I thought that I did eventually get it stopped.

The test drive around the neighborhood went well, and 15 miles to work today also did well. On the way home I lost the front brakes, so I still have work to do. I presumed that all of the front fluid leaked out of the fitting that must not yet be tight. I did not get to go under the truck to look at it, and it will be next week before I will be able to work on it. I did check the master cylinder, and found the reservoir for the front brakes is still half full. I expected it to be empty because of having no front brakes.

So, I have the question: Why do I have half a reservoir of fluid, but no brakes?

Thanks.

[Robert Crandall]

Forgot to add: 1978 C20, 292, 2WD, granny gear 4 speed.

[Dead Parrot]

If the master cylinder has several years on it, possible it has corrosion and a rough cylinder just beyond where the brakes normally operate. When you had your leak, replaced and bled the brakes, possible you operated the MC piston in the corroded rough area, damaging the rubber seal on the piston. Once the seal is shot, your brakes suck.

Those front hoses are a PITA.

[Robert Crandall]

Yes, thanks. I have had that happen multiple times - bleed the brakes then buy a master cylinder. I installed this one in 8/2015, so I do not expect that problem here, but anything can be possible. I will fix the leak at the connection then go from there. Having no brakes while having a half full reservoir is a new one for me, but it does suggest there may be a problem with this master cylinder that has not even started to rust yet. It was a rebuild, not a new one.

I agree, those front hoses are definitely a PITA. The connections at the calipers are easy to work with, but each of the other two connections are projects.

[Robert Crandall]

My third attempt at fixing these front brakes was successful. I bent my flare nut wrench to let it get a better bite on the flare nuts. That got it tight enough to no longer leak.

So, I moved to the rear brakes. When I installed the front lines in 2004 I could not get the supply hard line loose from the rear flexible line, so I left it. This year I soaked the connections for a couple of weeks before trying again. It turned out that a pipe wrench did break that connection free, so the new line is installed.

Now there is a problem with bleeding the rear lines. It appears they are air locked somewhere and will not bleed. Having the bleeder screw open and pumping the brakes gave about an inch of fluid in the catch cup for the bleeder hose, but nothing after that.

Is there a suggestion for fixing this? Do I need to bench bleed the master cylinder?

Thanks.

[Pontiac1976]

I would try this first. leave your bleeder open on the far side first, take off the rear line at the portion valve @ the frame( plug hole for the test) blow air throw line see it come out the rt rear. then open lt rear do the same thing. If no fluid or air come out it plug some where to the rear. if it does then there is blocked from the vale up to the master. Make sure to wear safety glasses

[Robert Crandall]

Thank you for your advice. I'll hold it for now because I believe I may have it fixed again. I have thought that before but was quickly proven to be wrong, so I hesitate to claim full success yet. A friend told me that he had just bought and had success with a brake bleeder kit that works off an air compressor and offered to let me borrow it. I tried it this morning. It was easy to use, and it seems to have been successful. The brakes feel very good on a short trip around the neighborhood, actually better than they have felt in a couple of decades. Maybe I have had air in the lines for a long time. I'll report again after a trip to work and back which will include multiple fluid level checks.