Service manager comment - need inputs on brake lines

bmninada

Contributor
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2016 CX-5 AWD GT+iActive Soul Red
As I mentioned in some threads the service manager for Mazda happens to know be a close acquaintance of mine. He used to be gear head and you might have actually seen him in one of the F&F movies even! Anyways he has always given me good advice. 1 thing he mentioned is he has started to see few repairs 2014, 2015 and before of CX5 where even after brake oil flush quality of braking (in terms of mushiness - the word he used and he said softness) did not improve much. After investigation he is finding softness and swelling in the brake lines but no leaks. He was suggesting (as the manufacturer or quality has not changed between generations of CX5) to think of upgrading to better brake lines and might as well think of braided (not sure what that means). He said risk is relatively low in terms of leaks but mushiness (again the word) might increase with # of years more than other comparable cars. 1 more thing: he said BRAIDED would be LEAST favorite option as they ALWAYS cause leakage in the fittings sooner or later.
 
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Toronto, ON
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2021 CX-5 GT Turbo
He meant steel braided brake lines. The steel braids make the lines more rigid and do not allow them to expand as much under heavy braking. I don’t think they are needed for a regular street driven car. The mushiness you feel is mainly due to the brake fluid.
 
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Ottawa, Ontario
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17 Mazda 6 GT
I doubt this will be an issue (yet) on newer CX-5's but his happened to me with an older vehicle:
My brakes were mushy and slightly pulling to one side, plus it appeared that the caliper piston wasn't fully retracting when getting off the brakes. The brakes got very hot too.
After much trouble shooting and parts replacement, the problem was still there.
The actual issue turned out to be a soft brake line that had collapsed internally.
From the outside, it appeared normal, but the layers on the inside had delaminated and collapsed, preventing the brake fluid from "reversing", thus causing the caliper piston to stay engaged and the pads still pressing on the disc.
Replacing the short rubber brake line at the caliper fixed the problem.
All in all, I think on an older vehicle it's probably a worthwhile investment to replace the original rubber brake lines with a metal or braided type.
 

bmninada

Contributor
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2016 CX-5 AWD GT+iActive Soul Red
Metal or braided type - as per my SA has its own issues. He said even top end performance cars like Porche, Massarati, etc. are using rubber hoses. The issue is flexibility and metal/braided lines tend to last less and fail at the fittings' end ; unless some really high-end lines which has swivel fittings. Then extreme care by a really good mechanic is required on how to route the line so that least resistance occurs. He said he did it to his own Miata and he trusts no one.
 
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CX5 2018 GT
yes, most are using rubber ones. rubber depending on how quality it is, ages. 5 yrs probably not an issue. 10+ who knows. the brake lines are maintenance items after certain age.
 

bmninada

Contributor
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2016 CX-5 AWD GT+iActive Soul Red
I spoke to him and he completely agrees. 2 points (I showed him this thread). He said 100% correct. Only thing he mentioned was he was forced to review the condition of brake lines AFTER he changed brake fluid but still found not good (braking). That is when he is seeing vehicles CX5 2014 and before seem to have this issue more. He changed the line set for 1 such car and the mushiness disappeared. At the same time he said he is seeing this for a subset, i.e. mostly 2013 and 2014 vehicles. He has reported it to Mazda Corp. There is currently no STB from Mazda on this. All he said is he recommends, if car is +6 to 8 yrs to have the line set replaced. He said its not costly, even with labor.
 
The problem with the steel braided lines is that it may be hard to find DOT-approved since they can't be inspected under the braid. Race cars use them, but those are harsher conditions and they are replaced regularly. Newer lines may be certified, but this wasn't always the case.

If the brake hoses are starting to deteriorate, you can only tell by cutting them open unless they are really bad. The inner walls will be obviously broken down. But I wouldn't expect an issue until 15 years or so. That's the rule of thumb replacement period for classic cars.
 
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2019 CX-5 GTR
The problem with the steel braided lines is that it may be hard to find DOT-approved since they can't be inspected under the braid. ...

No.


and you can surely find DOT approved stainless steel braided lines
 
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Virginia
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2021 CX-5 White
And just for clarity, stainless steel brake lines are really "rubber" or other material, which is then "armored" by the stainless braided covering. Just like the stainless steel braided water lines you get for toilets and sinks. They are still rubber inside the stainless. Pretty hard to make a fluid tight stainless steel woven braided line when you think about it.
 
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and you can surely find DOT approved stainless steel braided lines
Thanks for posting that. Like a said, these may be easier to find now (I realize I should have probably said "DOT compliant"). But I think years ago they were harder to find, at least for Porsches, which was my interest at the time. I don't think they made German TUV-compliant then either. I've never considered them necessary.

Your link also supports the rest of my comment:
"Here's the thing, though: Since stainless-steel lines don't bulge as they age, and since the inner Teflon lining is hidden behind the braid, there's no easy way to inspect the lines for warning signs of imminent failure.

This is no big deal on a race car, since the lines are (or should be) replaced at least once a season. On a street car, where most people are likely to let YEARS go by without even looking at their lines, it can be an issue."


And:
"If you do decide to put stainless-steel lines on your car, you need to be aware of a few things:

1. When you install them, you must make SURE that they can't kink, twist, or stretch under any combination of wheel droop, bump, or (for the front wheels) steer.

2. The stainless-steel outer braid will cut through anything against which it rubs, so you have to make sure that the lines don't rub back and forth over anything important.

3. Stainless steel lines have been known to fail when dirt gets between the outer braid and the Teflon lining... As the braid moves back and forth, the dirt abrades the Teflon and can make it rupture. If you look at stainless-steel lines on motorcycles, you'll see that many of them are encased in plastic tubing, apparently in an effort to eliminate this problem. The tubing also helps considerably with the abrasion issue mentioned above."


They look cool, but I just think they are potentially more trouble than they are worth. YMMV.
 
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Phoenix
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2020 CX5 signature
What about a master cylinder brace? My Google search seems to have found a couple, maybe a nice $125-$175 Saturday morning project?
 
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