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SS brake lines bad

If a car has been sitting or if the brake lines are very old can SS BRAKE lines go bad
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Old 05-29-2019, 12:25 PM
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YES, most folks recommend switching back to the rubber ones.
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Old 05-29-2019, 01:12 PM
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Quote:
Originally Posted by T77911S View Post
If a car has been sitting or if the brake lines are very old can SS BRAKE lines go bad
The thing that causes ss lines to deteriorate is grit that gets into and under the ss sheath, this eventually grinds through the liner.

Inspect for leaks when it's put back into service and replace as necessary
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Old 05-29-2019, 03:52 PM
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Quote:
YES, most folks recommend switching back to the rubber ones.
I didn't use them on my car because you can't see the rubber part to know if they are deteriorating - you can only see the Stainless Steel covering that may look great.
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Old 05-29-2019, 04:07 PM
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Stainless brake lines look nice and are easy to sell...that is why they exist. There is no need for them unless there is some contact rubbing that should not exist anyway.

Old brake lines need changing regardless.....the rubber tends to swell over the years creating a smaller channel for the fluid and also hardens in areas that can cause failure.
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Old 05-29-2019, 04:12 PM
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Well, I've had the same SS brake lines on my SC since the late 1980s. I semi-covered them with that spiral wrap plastic used to cable small electrical wires together, though thinking about what Bill V had to say that may have been counterproductive. But they have performed flawlessly. They predate, I think, the existence of DOT approved versions which now are available.

Unlike rubber, the Teflon or whatever plastic is used as the actual line doesn't deteriorate under the influence of brake fluid. Flush the old fluid, replace, bleed, and go - as long as inspection, with someone standing on the brake pedal, doesn't show any leaks. But just sitting isn't going to cause any problems here to the lines.
Old 05-29-2019, 06:01 PM
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SS brake lines made in the last 20 years would be PTFE Polytetrafluoroethylene (aka Teflon) tube with stainless braid over them. If they are DOT approved they should have double lay lines that are printed on the hose running down the length of hose as well as a date of manufacturer. Since you can't very well print onto stainless wire, they will also be covered in a pvc covering that also protects the stainless steel braided from sawing thru items it rubs on.
PTFE will last longer than most owners will have their cars. Where as the rubber cloth enforced factory lines are recommended to be replaced every ten years if they have brake fluid in them. That stuff is nasty and eventually can breakdown the rubber. Rubber gets hard and brittle with age as well. Hence the shorter lifespan.

The performance benefit of a braided lines is in the fact that they don't swell under pressure nearly as much as rubber lines. That results in a firmer pedal feel and more immediate response.
Hose manufacturers pressure test their lines and should be able to provide a burst pressure and an expansion metric. I used to be a dealer for BrakeQuip and their PTFE hose supplier had a burst pressure of 15,000 psi or so I wanna say. Way more than your master cylinder is capable of. The rubber hose expanded under pressure quite a few times more that the PTFE did as well. SS lines really do perform better and outlast their rubber counterparts. Real live science to back it up.
Old 05-29-2019, 06:30 PM
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I'll second Pampadori's remarks... having made up my own sets many times.
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Old 05-29-2019, 09:05 PM
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these are on a race car that was built around 86.

I am have trouble getting them bled for one thing. the other is it seems like the fluid flow, especially out of the rear ones, is not very strong.
I know the rubber lines can swell and not release the calipers, but do you think the SS lines could be restricting the flow? it does seem like the calipers are not sticking from what I can tell. I can still roll the car around if I need to.

new MC's
I pulled all the pistons out of the calipers and cleaned them.

my pressure bleeder wont fit these MC's so I was about to take it to a shop today but then I thought about the old SS lines
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86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
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08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 05-30-2019, 02:46 AM
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end of last year one of my rear brakes started dragging on the 84 928. over winter first rebuilt all calipers, one of the few things I had not done to this car. same rear was dragging. after some testing found that line was restricting the return flow and maintaining some pressure on the pads. even when a line is badly restricted it will let the high pressure of the pedal to go out into the caliper but may not release all the pressure. and the same when trying to bleed if you are using something like a motive pressure bleeder, just not enough pressure.

ordered a full set of lines. when I got them they were all steel braided with a plastic covering. installed and now both rears drag. then replace the MC and all it good again.

also had to rebuild the rear MC on my 83 Honda CB1100F due to leak. there is a very small pressure relief hole in addition to the one that allows the fluid into the piston. my honda guru friend reminded me to use a very small wire to ensure that pressure relief hole was clear. otherwise it will drag and can possibly lock up. got that rebuilt too.

good luck.
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Old 05-30-2019, 09:38 AM
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T77 - is this car a 3.2 Carrera? Those have a pressure limiting valve in the line to the rear brakes. You can see it (looks like a smallish fitting) in the line in the trunk. I don't know if those can clog some.

The problem with the swelling of the rubber lines has more to do with their collapsing when the pressure is off and restricting the return flow (thus causing drag) than it has with ballooning and somehow reducing the effective pressure at the caliper, from what I understand. Neither of those things are going to affect the Teflon lines.

The "proper" diagnostic approach would be to put a pressure gauge into the bleed valve hole on your rear calipers, and watch it when someone stomps on the brakes with the engine running (or a vacuum somehow introduced to the MC vacuum chamber). But that's a lot of work if you don't have the stuff.

It would be cool if there was a strain gauge (stress gauge, for compression rather then tension?)which was about the thickness of a brake pad.

These brake lines aren't all that expensive, so maybe the meat axe approach of throwing new parts at things could be justified?
Old 05-30-2019, 01:40 PM
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Old 05-30-2019, 01:50 PM
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Still rubber, so yes.
Old 05-30-2019, 02:42 PM
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Quote:
Those have a pressure limiting valve in the line to the rear brakes. You can see it (looks like a smallish fitting) in the line in the trunk. I don't know if those can clog some.
I replaced that on my 85 911 with a manual tilton valve when I upgraded the front calipers and was running it at DE. was able to completely open the manual proportioning valve due to the bigger front brakes. did the same when building my current 86 951 for DE. rebuilt the stock calipers, consequently I had to retain a lot of restriction with the manual valve or the rears would lock prematurely.

when doing the work on my 84 928, it also has a restriction valve on the rear lines. after replacing the brake lines and finding both rears dragging I suspected that. but from research and talking to a couple shops, one specializing in 928s, they had never heard of one of these fail. there could be the potential to clog but if you let your brake fluid get to that point ....

replacing the MC fixed it. when I was doing the MC I took a good look at that restriction valve. I could blow air through it, not sure how it works.

off to rebuild the AC system on the 928 today.
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Old 05-31-2019, 04:53 AM
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