Brakes locking on P30

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Brakes locking on P30

Home > Discussion Forum > Mechanic's Corner - Brakes

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All Messages in Thread	Author	Date
Brakes locking on P30	charles	10-31-04
I have a 1989 Coachman on a P30 chassis. The fron brakes started locking up after I purchased. The master cylinder had just been replaced twice. I replaced both front calipers and the front brake hoses and bled the system. I checked the rod going from the peddel to the hydro-booster and it is set so the hydro-booster completely disengages after the brakes are used. Any help would be appriciated. Thanks in advance, Charles
Re: brakes locking on P30	charles	10-31-04
Almost forgot. The belt on the hydro-booster was removed and the fron wheels still locked up while on the jack.
Re: brakes locking on P30	Jeff	11-13-04
After reading several othet posts from previous dates, check the brake light switch. It may stop the pedal from returning to the fully disengaged position.
Re: brakes locking on P30	frank burder	11-27-04
Anyone solve this problem???help??
Re: brakes locking on P30	Charles	12-5-04
Problem solved!!! We replaced the front calipers and pads. That didn't help, but they were old and replacing sure didn't hurt. We disconected the hydro-booste with the front lifted and the brakes still locked up. This ruled out the hydro-booster being bad. We replaced the master cylinder. The previous owner had already replaced it, but he used a rebuilt one. The tolerances are apparently pretty close, so the rebuilt one is a bad choice I think. I still had some noticeable drag. The P-30chassis has self adjusting brakes, but they only adjust when you drive in reverse and apply the brakes, so I backed up and applied the brakes pulled forward and repeated several times (I didn't have a large open area available to drive in reverse and apply brakes over and over.) I still had a very light drag. I couldn't tell except for the smell of brake fluid and the heat of the calipers after 30 minutes or so of driving. I took the RV to a medium duty GM service department (called an RV service center for advice). The GM tech said that the brakes just needed to be adjusted (I hadn't adjust them enough). It drives like a champ now. I have driven it a couple hundred miles and absolutely no problems. If the master cylinder hadn't fixed the problem there 2 other probable problems: 1. the proportion valve would have probably been the problem. The GM Tech said it's rare for the "prop valve" to go out, but it could. 2. the brake light switch on the brake peddle has been known to cause a light drag (the GM tech checked this when he looked at my RV). GM issued a Technical Update on the 1988 P30 chassis (not sure if the same update was issued on other year model, but I think that several year models were the same). I hope this info helps. P.S. - If there are no visible signs of problems with the master cylinder I would first try to adjust the brakes by backing up over and over and applying the brakes or driving in reverse and applying the brakes in an empty parking lot. I read somewhere that the brakes can get out of whack because they never get a chance to self adjust from lack of applying the brakes while in reverse.