Cleaning out brake lines?

The hard lines on the Vette seem to be packed full of crud, which isn't surprising considering the mud that came out of the master cylinder last night. I've tried spraying brake cleaner through them, which worked on the shortest one, but I'm not having any luck on the rest.

Should I hook up my air compressor and try to blow them out that way, or is there anything else I should try first?

How much are replacement lines? Safety equipment and all that.

In reply to RossD: Agree. Not really worth skimping on...

If there is gunk in all the lines I wonder how that's going to affect the ABS module? FWIW I think I may have one to my old car

Edit: I don't think 84 had abs

While I agree that replacement is probably a good idea, would fresh brake fluid and high pressure from the MC clear them out?

I wouldn't bother replacing all the HARD lines unless they look visibly bad on the outside. But I don't know whether it's actually possible to blow major crud out of a line that small just with pressurized air or fluid. If you try it, disconnect everything with a seal in it first, so you don't damage them. And start with the end farthest away from that master cylinder that is probably the source of the gunk.

For the soft lines, I would replace all of those as a matter of course on a 1984 sports car, and replace the caliper seals. I know they're going to leak eventually, so I might as well do it now instead of getting black-flagged at an HPDE and losing the day.

If you have a throwaway master cylinder body and reservoir (doesn't need pistons even), you could install it and fill the reservoir with acetone, and let the acetone gravity-bleed through the lines. It might eff up the seals in the ABS unit but it'll dissolve the crud.

It might also eff up the seals in the MC. But if you've got a throwaway MC that does have pistons in it, you could use vice grips to clamp off the hoses to 3 out of 4 calipers at a time, and use the MC to pressurize acetone through each line.

NOTE: these are things I would try, but I would employ appropriate safety measures and I'd encourage you to do the same.

AngryCorvair wrote: If you have a throwaway master cylinder body and reservoir (doesn't need pistons even), you could install it and fill the reservoir with acetone, and let the acetone gravity-bleed through the lines. It might eff up the seals in the ABS unit but it'll dissolve the crud.

If one doesn't have ABS, would this be a safe bet?

In reply to RevRico:

I don't know if it's "safe", but it is something I would try. E36 M3s already berkeleyed, trying this isn't gonna berkeley it more...

Correct, no ABS on mine and the soft lines are all new. The hard lines appear fine externally, but what remained in the reservoir seriously looked like mud. Since the master cylinder cleaned up ok I figured the lines probably will too.

Compressed air, brake clean, repeat.

You'll know when you bleed the brakes if they are all flowing well.

I'm pretty sure the mud is rust, having popped one at 75mph in traffic, I must say that rusty brake lines are not to be trusted. That said, IIRC isopropyl alcohol is the generally accepted brake system cleaner when switching between glycol and silicone based fluid so that'd probably be the stuff to use.

Pressure on one end, maybe some vacuum on the other. But I would probably plan on replacing them. These lines often rust from the inside out.

I'd wager that the amount of time spent cleaning might be in the ball park of time spent replacing, with the drawback of potential contamination from residual debris and with a huge unknown related to safety and lifespan of the old lines.

Bending and making new brake lines is not hard, just time consuming.

BrokenYugo wrote: I'm pretty sure the mud is rust, having popped one at 75mph in traffic, I must say that rusty brake lines are not to be trusted. That said, IIRC isopropyl alcohol is the generally accepted brake system cleaner when switching between glycol and silicone based fluid.

Your local electronics supply store (if one still exists in your area) should stock 99.9% pure anhydrous isopropyl alcohol.

Sounds like a great way to reveal a leak. By cleaning you might dislodge that one last layer of rust that was holding it all in. My last brake flush opened up a mid-body leak on the front-to-rear line, so that task got a little longer.

I worked at it some more at lunch and the lines seem clear now. I think the T at the rear of the car was most of the issue - there really wasn't much fluid or residue left inside them. Hopefully I can get them bled tonight.

I blew funk out of my lines with brake pedal pressure. Took the bleeder all the out of the passenger front (where my issue was) and stood on the pedal. The system shot its load out like an adult film star. I bled the brakes and all has been well since. Four years.

Sounds like you got it sorted but to add to this if the contamination is from a rusted master the odds are that the contamination is only in the lines running from the master. I would disconnect the lines at the master and push fresh fluid backwards through the lines. Usually a piece of efi fuel line a couple small hose clamps and compressed air will do it. It is messy and be prepared for the spray of fluid you are going to get. Additional fuel line clamped to the open lines by the master directed in to something away from the car can help keep things a bi cleaner. Remember brake fluid will strip some kinds of paint.