rick deckert Posted April 5, 2014 Share Posted April 5, 2014 hi everyone! replaced master cylinder on a trip last summer and haven't had any problems until coming home from wintering in florida! about 20 miles from my home in south central wisconsin i stopped to see my daughter and when pulling up to stop sign my brake pedal became hard and front brakes started dragging! made it to her house a block away and came back out and checked them and they had released, drove on home with them still acting like they wanted to lock again! any ideas what could be causing this? master cyl. i purchased last summer is under warranty so i picked up another one today to try! thanks Quote Link to comment Share on other sites More sharing options...
Derek up North Posted April 5, 2014 Share Posted April 5, 2014 My first guess is one of your brake hoses. Is there any way you can jack up the front end to see if it's one or both wheels that's locking? Quote Link to comment Share on other sites More sharing options...
rick deckert Posted April 5, 2014 Author Share Posted April 5, 2014 I have checked the rotors after they locked and both are locking at the same time! motorhome is 1989 dolphin v6 with 65000 miles on it! did wheel bearings and checked rotors and pads before the trip and pads looked as if they had been replaced recently rotors looked almost new! also bled and flushed brake fluid after removing proportioning valve in the rear! brake rod from pedal to master cyl. seems to have right amount of free play! outside appearance of brake lines look good but that doesn't mean there good inside! leaning toward trying new master cyl.and see what happens! need too get it dialed in before Alaska trip in june! thanks Quote Link to comment Share on other sites More sharing options...
fred heath Posted April 5, 2014 Share Posted April 5, 2014 Seized caliper(s), or defective proportioning valve. Are you sure you hooked up the proportioning valve correctly? Quote Link to comment Share on other sites More sharing options...
rick deckert Posted April 5, 2014 Author Share Posted April 5, 2014 hi fred! completely removed the proportioning valve last summer before trip to superior! much better braking without it! have drove over 6000 miles before this problem happened! checked the one way valve on brake booster about hour ago and it seems to be working the way it should! have heard of brake lines heating up near exhaust manifold on the v6 but most the problem occurs when there is moisture in the lines and when it heats up it expands causing brakes to drag! thanks for the reply! Rick Quote Link to comment Share on other sites More sharing options...
Maineah Posted April 6, 2014 Share Posted April 6, 2014 If they are locking up open the bleeder and see if that frees them. If it does back the nuts off that hold the master cylinder to the booster and see if that frees them once they lock up again.The boaster is more likely suspect than the cylinder. The valve in the boaster keeps vacuum in the booster when the engine is off that's it's only job. If there is moisture expanding it will push the fluid back into the master cylinder and if there is that much moisture in the system more than likely you would loose pressure not gain it as the water boiled after all brake fluid expands all so when it gets hot. Quote Link to comment Share on other sites More sharing options...
rick deckert Posted April 7, 2014 Author Share Posted April 7, 2014 replaced master cyl. and this time looked at parts diagram it shows gasket between master cyl. and brake booster! also found a vacuum hose that was unhooked and was leaking alot of vacuum so maybe this will take care of my brake problem! going to take it on test drive today will see if problem is solved! thanks all! Quote Link to comment Share on other sites More sharing options...
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