Stuck Rear Brake Caliper, the cause.

Rupunzell

Rupunzell

Bernice Loui
The 74' developed a dragging rear brake caliper not too long ago.

This is usually caused by a stuck brake piston or a brake hose that is closed down over time that the hose no longer allows any fluid flow. Third is the brake master.. which happens less often.

In this case, it turns out to be the hose. Over time, the rubber expands internally causing the ID of the hose to shrink and eventually shrink to where near zero flow occurs.

Here is the problem hose connected to the pressure bleeder unit with the regulator set to 60 psi. Notice there is little of anything exiting the other end of the "open" brake hose.

This hose is far past it's replacement date and it has cracks all over the outside of hose casing.

Basically, replace ALL brake hoses as a maintenance item., not when they have problems or fails by constriction.

74%2520exxe%2520Stuck%2520rear%2520brake%2520hose%2520%2540%252060psi.jpg



Bernice
 
Good photo and message Bernice. We all tend to push brake hoses longer than we should!

Worth mentioning that the reason that calipers tend to "stick" is because the "push" pressure will be more like 1,000 PSI - so a restriction would need to be BAD to not allow fluid to PUSH through - however the return pressure is much lower - hence collapsed hoses tend to become 1 way valves.
 
Good illustration...

Good illustration of a problem that many of us are intellectually aware of, but probably never test as you have. Now we have proof! :geek:
 
That is pretty much what happens. The tired brake hose becomes a one way check valve. 1000 psi is a typical brake line pressure.. and it could go higher than that. Light braking produces 300psi or so.

Keep these pressures in mind when looking at those brake lines, fittings and hoses. If is also why compression fittings should not be used.. even at times they are.

There was a time when the metal brake lines would corrode resulting in soft spots in the tubing that fail without notice causing brake failure.

This was addressed by copper-nickel tubing in the late 1960's and early 1970's. Some vehicles used polymer coated tubing which worked OK as long as the coating was not damaged.


Bernice



Franken said:
Worth mentioning that the reason that calipers tend to "stick" is because the "push" pressure will be more like 1,000 PSI - so a restriction would need to be BAD to not allow fluid to PUSH through - however the return pressure is much lower - hence collapsed hoses tend to become 1 way valves.
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