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Discolored brake line
- Thread starter seagull
- Start date
Walt---somewhat strange. We've seen discoloration when a black adel clamp is around hose, but not like you have here. Looks like the discoloration is internal?
I posted this picture open the thread where a fellow talked about discoloration on his static line. This is poly (I think) that has just been sitting on my scrap hose box for ten or fifteen years. No idea why it discolors…. I agree with Tom that I have seen transfer of color from Adel clamps. But this has never been used for anything!
Polyethylene tubing discolors in UV light and some chemical reactions that speed oxidation. Becoming a big problem with PEX tubing plumbing. Usually a sign of age and degradation of the product and consideration of replacement is appropriate.
Polyvinyl tubing which is what it appears Paul's example is turns brown with UV exposure. Rate of change dependent on the plasticizers used i.e. quality.
Polyvinyl tubing which is what it appears Paul's example is turns brown with UV exposure. Rate of change dependent on the plasticizers used i.e. quality.
I’m fairly sure the lines are nylon not poly.
Shameless plug.Poly and nylon are completely different materials that “look” similar. I use TS Flightlines on my gear legs and only recommend their hoses. In the cockpit the room is limited so the nylon is a good choice plus the ability to “see” the fluid.
I don’t think this discoloration is heat related since the location is in the tunnel and the other 3 are not showing the same. This is also the same reasoning to rule out UV issues. It may be caused from brake fluid sitting on the outside of the tube. That fitting did have a tiny leak several years ago.
I don’t think this discoloration is heat related since the location is in the tunnel and the other 3 are not showing the same. This is also the same reasoning to rule out UV issues. It may be caused from brake fluid sitting on the outside of the tube. That fitting did have a tiny leak several years ago.
I think John has it on the correct answer. Make sense even with Pauls hose. The pattern is kinda weird, but makes sense.
I wonder if that park brake valve had some sort of lubricant that reacted with the tubing.
Ralph---i dont think so---Pauls example was a hose that wasnt attached to anything, but was discolored. No fluid had been run through it.
I have to say, thats weird----other than a different lot of hose, or from a different manufacturer, with a slightly different composition.
It is the exact same hose on both sides of the valve, only cut to put the valve in.
It looks to me (based on the hole just below the valve) that the discoloration is at the location where the adele clamp was prior to installing the valve.
Good hypothesis - you can see where the Adel clamp rubber discolored the area around the hole….
Excelent work Sherlock!
I am checking with the original builder if he recalls a clamp, the evidence on the sheet metal is enough for me, that makes perfect sense. The other -12 I am familiar with that has the same stains on the brake line and Just had the parking brake valve installed by me. Looking at the before and after pics the adel clamp was the cause of the discoloration. Thanks for the good sleuthing, I was ready to replace brake lines.
Yes, good sleuthing -- a previous adel clamp seems suspect, and it appears both lines are stained at the same location. I'm also curious about why both lines appears discolored, though to a lesser degree, along their entire length, or the fluid seems to have changed color.
Yep---that now id beginning to make some sense. I assumed the valve was an original install, not an add on. My bust for the assumption. My sleuthing skills are fading I guess
Picture of an original classic installation, no parking brake:
For what it's worth, this is a recent picture of the brake lines and adel clamp installed 15 years ago. There is no indication of staining from the adel clamp. If you look at the adel clamp in post #10 lower right; you can see staining there on the tubing.
For what it's worth, this is a recent picture of the brake lines and adel clamp installed 15 years ago. There is no indication of staining from the adel clamp. If you look at the adel clamp in post #10 lower right; you can see staining there on the tubing.
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I was in my “random hose box” yesterday looking for a short piece of tubing and realized that I have a bunch of rubber (or whatever passes for rubber in the automotive world these days….) vacuum line in there. When I look back at the picture of the discolored hose that I posted (above), it is possible that it was in contact (at random places) with that rubber hose (similar material to the padding on an Adel clamp), and that might explain the discoloration on that piece. Or its a complete red hearing, but at least we can be consistently wrong if that’s the case…
great probability Paul----I was in my “random hose box” yesterday looking for a short piece of tubing and realized that I have a bunch of rubber (or whatever passes for rubber in the automotive world these days….) vacuum line in there. When I look back at the picture of the discolored hose that I posted (above), it is possible that it was in contact (at random places) with that rubber hose (similar material to the padding on an Adel clamp), and that might explain the discoloration on that piece. Or its a complete red hearing, but at least we can be consistently wrong if that’s the case…
