The Roadmaster is once again a Drivewaymaster.
The brakes always had a typical full-of-air spongy-ness to them so I figure it's time for a good drain and bleed. Fluid is dark and murky so I do the classic two person bleed from RR, RL, FR, to FL until fluid is clear and bubble free. Flawlessly done, or so I thought.
Start it up and the first sign is the red "brake" light on. Second sign is the soft pedal. It will stop, and even lock and engage ABS, but it feels 50% less confident than before I even touched it 
Pull back in the driveway and notice a long line of dripping coming from the frame, where the front-rear line runs. But maybe that's just from fluid splashing everywhere since I left the MC cap off during the bleed. Oh and the reservoir has lost half its fill during a short drive.
My question: is it possible to over-pressurize the system during the bleeding process? Perhaps the cycling and holding of higher-than-usual brake pressure was the last straw for a rusted pinhole leak just waiting to strike?
GM parts that are 20 years old living in the rust belt..... Hard lines can pop at any time and for literally NO reason whatever.
'99 Suburban (not even particularly rusty) had a line break last month after jump starting the battery in the driveway.
It is not possible to over pressurize the system if it's in good shape, you should be able to kick the pedal idling in park and not blow anything.
Light surface rust on the lines is ok, heavy is time to replace, "tree bark" scale means you really shouldn't drive it, just touching those hard enough to flex them will make them leak. The OEM "kink proof" lines with the wire wrapped around them are the worst, they can look kinda ok and be ready to pop.
Sounds like the "stuff" that was in the lines that you flushed out was self sealing the hole. New fluid = no more sealing of the lines from the inside. . . .. . It is a theory anyway.. . . . 
I've popped more brake lines bleeding than any other way. I don't know why It usually happens that way, but it's better then than coming into a red light or when some stupid cow in an Explorer pulls out in front of you, across your lane, then stops.
Not only is it not-uncommon to blow lines while bleeding brakes, it's also fairly common to wreck a master cylinder when you full stroke it if it has nasty fluid in it. Rust can build up in the bore in the normally never used part of the stroke, then when bleeding the brakes you scrape the seal over the rust and now you get a sinking pedal.
I always figured, this was the car's way of punishing you for not flushing the brake fluid every two years like you should.
Aaand it just occurred to me why Girling made such an incredibly goofy (by modern standards) design for their master cylinders, as copied by Tilton and Wilwood and probably a dozen others. It doesn't stroke the seal over a port.
Rather often. Usually with my luck its after replacing one line. I end up replacing 2-3 lines everytime.
I gave up on my zephyr and just replaced all the hoses and lines.
Knurled wrote:
Not only is it not-uncommon to blow lines while bleeding brakes, it's also fairly common to wreck a master cylinder when you full stroke it if it has nasty fluid in it. Rust can build up in the bore in the normally never used part of the stroke, then when bleeding the brakes you scrape the seal over the rust and now you get a sinking pedal.
This is full of truthiness.
I just did last week. Replaced the leaking master, then the wonky prop valve, and THEN blew a hard line bleeding.
Fun times.
i did it on the 92 roadmonster. replaced the calipers, hoses, rotors and went to bleed. had it feeling great, went for one more pump, foot to floor. found the weakest rusty line, then replaced them all.
patgizz wrote:
found the weakest rusty line, then replaced them all.
Well there's another line item on the $2016 Challenge budget 
Guess it's time to buy a bender and flare tool.
Thanks everyone for the reassurance that I didn't totally mess up a simple job.
Yup, it happens. I made a panic stop once and everything was fine, then a day later a line busted with modest pressure.
But bleeding can make some higher pressures if the operators foot gets too far out of synch with the bleeder's wrench. Plus, when you are bleeding the fronts, the rears are seeing pretty high pressures with the pedal to the floor.
Yep, developed a leaking rear wheel brake cylinder when getting my Opel GT back on the road so I ordered a replacement cylinder. I put it on and was bleeding the brakes when the other wheel cylinder on the other side blew. Shoulda figured that if one cylinder blew on a 40 year old car the other one was soon to follow. From now on when I have on issue on one side I automatically replace both sides.
20 years on salty roads? Its due. Better in the driveway than on the highway.
brake lines not a challenge budget hit.
Kind of like dealing with burst frozen pipes. Fix the part that you know is leaking. Refill and repressurize the system, and blamo another weak spot bursts. The difference being with frozen pipes, you never know when it will stop bursting other spots until it finally holds and you get paid. Then somebody else gets to clean up the mess.
When a brake line is leaking its best to just accept the fact that you are going to replace to bunch of lines before you even look under the car. If you think you are going to just patch in were the leak and be done, You're gonna have a bad time.
Funny, I got a stuck rear brake caliper on the mercedes so I rebuilt both rear brake calipers, the brake isn't feeling very nice, I notice that one of the front brake calipers blew out a large amount of brake fluid. I've never had anything make a mess like this brake fluid, I hate project creep. I had to use the brake to push out the stuck cylinder, I think it decided to go then. Waiting on the parts to come so I can find the next weakest link.
I once had a master cylinder's seals blow out during bleeding, right after I cooked the brakes at the track.
One broken line turned into a new master, new lines, new hoses and wheel cylinders. Rebuilt calipers and now the issue is an NLA prop valve!
Brakes dont like me.
I don't mess around when that happens. It is a pain in the butt, but for under $200 you can buy a complete stainless pre-bent set of lines from Inline or Classic Tube. Just do them all.
maschinenbau wrote:
patgizz wrote:
found the weakest rusty line, then replaced them all.
Well there's another line item on the $2016 Challenge budget Guess it's time to buy a bender and flare tool.
Thanks everyone for the reassurance that I didn't totally mess up a simple job.
Also, look for the nickel-copper alloy lines. They bend easily.
curtis73 wrote:
I don't mess around when that happens. It is a pain in the butt, but for under $200 you can buy a complete stainless pre-bent set of lines from Inline or Classic Tube. Just do them all.
Ugh. I hate doing those. I'd rather make my own. Stainless is VERY difficult to bend. So, between them not bending them 100% accurately, and having to either mangulate them a bit and/or pull the body off of the frame to get them installed, and then try to de-mangulate them in situ (which as before is difficult because stainless is VERY difficult to bend by hand) they are always a PITA.
I mush prefer the nylon coated line. It bends far more easily than regular Bundy line, and it holds it shape better than the copper coated stuff. I usually make lines by duplicating them off-chassis and then installing them, and the copper coated stuff is WAY too floppy for that to work well.
Sadly, I usually get to make/install about 100 feet of brake line per month on average. Really sucky job if you want it done Right.
