Hydraulic Lock in Disk Cylinder Brake Line


Old 02-25-02, 05:34 PM
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Question Hydraulic Lock in Disk Cylinder Brake Line

92 Dodge Grand Caravan 260,000 km / 160,000 miles
Passenger side disk caliper seemed to be slow to release - replaced with rebuilt caliper yesterday. Today the brakes overheated and I discovered that the hydraulic pressure is not being released properly when the brake pedal is release - the pressure release is very slow and required heavy pressure (with a C-clamp), but when the bleeder screw is open - no problem piston retracts normally. No sign of damage to the brake line itself and fluid flows freely during bleeding. Wondering if this could be a problem with the mechanism of the differential valve (the valve that splits system diagonally and has the warning light built in?) or is it more likely to be a problem with the master cylinder - I assume the master cylinder actually has the valve that releases pressure. I loosened the master cylinder line fitting just a bit but that did not seem to help (although I only loosened it a bit). Any help appreciated.
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Old 02-25-02, 08:28 PM
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It sounds like a faulty brake hose to me.They'll bleed fine but won't release or flow the opposite direction(it makes it act like a one way check valve.You can loosen the hose at the point where it attaches to the steel line and see if the piston can be pushed freely,if not then replace the hose.
Old 02-25-02, 08:41 PM
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I agree with fordtech's diagnosis.

I'd like to add that you should probably replace BOTH front brake hoses at the same time. The driver's side hose is probably just as old and nearly as deteriorated as the pass. side hose.
Old 02-25-02, 08:44 PM
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I agree. Pitch the rubber lines for two new ones. Have seen it time and time again when they rot from the inside out and get old like that.
Old 02-26-02, 05:33 PM
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Thanks - right on the money - replaced the hose and she'll retract by hand. Never had to replace one before, except maybe due to physical damage - now I know what to look for. Ofcourse I twisted off the brake line - even after heating it (I discovered silicon brake fluid is quite flammable) - I can never seem to remove an old brake line fitting without twisting off the line - any tricks there?

As for the driver's side - it still retracts easily by hand so given my luck with brake lines I think I'll leave it alone. Not sure how much longer we'll be keeping it anyway.

Old 02-26-02, 08:17 PM
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Don't cheap out. Replace 'em both. One side is rotten the other is not far behind. The hoses are cheap. Life is not.

As for the brake lines, Chrysler lines are made of gum. My friend broke his on his 1991 Shadow long ago and we broke a few in the junkyard (he wanted to prove to me that it was made of gum...lol). Wound up flaring up a new one.

You might be able to buy prefitted lines from Chrysler but they will be pricey. There are companies that can fashion new lines from your old ones quite reasonably.

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