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Stock JK TechBulletin board forum regarding issues with OE (original equipment) components of the Jeep JK Wrangler (Rubicon, Sahara, Unlimited and X) such as factory suspension parts, engine, transmission, body parts, interior fixtures and the on-board computer.
Pressure on the line causes the line to swell, releasing the pressure causes a slight vacuum on the line which causing the old line to collapse and basically sealing in the fluid. This means that the majority of the hydraulic pressure is off of the piston, but there is still enough there to maintain contact with the rotor causing the brakes to stick.
Stretched, sagged, hot or old, the stock lines work for basic road duty but will fail on heavy duty use after a while.
Pressure on the line causes the line to swell, releasing the pressure causes a slight vacuum on the line which causing the old line to collapse and basically sealing in the fluid. This means that the majority of the hydraulic pressure is off of the piston, but there is still enough there to maintain contact with the rotor causing the brakes to stick.
Stretched, sagged, hot or old, the stock lines work for basic road duty but will fail on heavy duty use after a while.
While brake lines can cause issues with calipers not releasing properly it is not as stated above. If you have an open return port you on one side and pressure built up on the other side, the brake hose wouldn't stay collapsed. The pressure would push the hose back open and return to the reservoir, therefore releasing the brakes as it should.
The issues found where break lines were the problem claim there is a break down internal to the hose for example the inner layer delaminates and creates a check valve. While I see this as possible it is very unlikely in a 5-10 year old vehicle. Typically hoses are designed to last 10-12 years or longer for the fluids in which they carry with only visual inspections as maintenance.
The much more probable reasoning and the only ones I've seen first hand (as a mechanic) is restrictions. Anything from a kink in the line from replacing pads or calipers the first time (either from maintenance or repair of an originally failed component), extremely contaminated brake fluid causes a restriction in the hose (only seen this in older vehicles allowed to sit and the water absorbed into the fluid causes rust in large particles), or the one that I've seen/heard most common is the metal brackets that the hose runs through, rust and causes an external squeeze which causes an internal restriction. All of these don't actually create a complete "check valve," but instead cause the caliper to react slower. This in turn causes excess heat to build on the pads and calipers each time the brake is applied and released. The cycle continues by expanding metals making tolerances smaller and the issue just gets worse.
To OP, I'm not saying replacing the hose isn't what fixed your issue. Just wanted to offer some insight on some possibilities behind why a "hose" could present issues.
The right front brake assembly on my son's 2012 JK Sahara was overheating intermittently. We replaced the pads, rotor, and caliper thinking this would fix the issue. As it turns out, the problem was the flexible brakehose between the caliper and the connection to the rigid brake line. The hose had collapsed internally at the crimped bracket that attaches to the spring base. Here are the photos: On the left is the normal opening of the hose and on the right is the cross section of the hose crimped in the OEM clamp. This is a photo of the OEM clamp and hose cut down the middle to show the crimped hose that caused the issue.
08-25-2017, 12:39 PM
