boatbum Posted July 17, 2003 Share Posted July 17, 2003 Since you all have been most helpful with my VR - I have a question about one of my other rides. On one of my Dakota '89 convertible pickups the brakes are way soft. The pads and rotors look ok. The brakes work but when stopped the pedal will continue almost to the floor over about a minute. When first pushed they seem ok but not hard but they get softer as I apply slight pressure. When I remove my foot and push the pedal again I have full pressure and then it slowly sinks. So I figured I have a leak or air. The master was full so I bled the system, filled it up and it is still doing this. It has been about 3 weeks and it is still totally full. Any ideas before I give up and head to midas. Thanks for any input. Teo Quote Link to comment Share on other sites More sharing options...
Tim240z Posted July 17, 2003 Share Posted July 17, 2003 Drum brakes in the rear? That is where I would start! Tim Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 18, 2003 Share Posted July 18, 2003 Sounds like a bad master cylinder. Its been a while since auto shop, but I believe the primary cup (?) is the name of the seal that actually pushes the fluid. If the front primary cup goes bad, the fluid can pass the secondary cup and return to the reservoir, without actually exiting the system. If the rear primary cup blows it will usually leak brake fluid into the booster. You can look for a leak at the back of the master and see if there is fluid there (usually seeps). Put light pressure on the pedal, hold it there. If the pedal slowly sinks to floor, then the master is bad. Its not a bad idea to check for other leaks like wheel cylinders and calipers, but you said the level was the same, so I'm thinking the master is the culprit... Jon Mortensen Quote Link to comment Share on other sites More sharing options...
boatbum Posted July 18, 2003 Author Share Posted July 18, 2003 Thanks Tim and Jon, I will check both out. I am also guessing that the Master is bad. I didn't know how the Master worked and on my other cars when the Master was bad - it would actually leak. Thanks for info - I will hunt around for a new master today and throw it in. Teo Quote Link to comment Share on other sites More sharing options...
Guest billy383Z Posted July 27, 2003 Share Posted July 27, 2003 Sound like possibly a slow vacuum leak in the booster? Long, long ago in a place not so far away, I had a '75 Chevy Monza that had exactly the same symptoms. Booster would hold vacuum until brakes were applied, then the pedal would slowly ease towrds the floor while you were stepping on the pedal. Bad part was the new (re-manufactured) booster cost more than the rest of the car was worth. Never fixed it, sold it. Somebody else's problem! Quote Link to comment Share on other sites More sharing options...
boatbum Posted July 27, 2003 Author Share Posted July 27, 2003 Thanks for the help! It was the master. Didn't realize the master could leak and not loose any fluid. Now if I can just get my VR finished and on the road... Teo Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted July 27, 2003 Share Posted July 27, 2003 A little rust in the MC and the rubber seals won't seal to the inside of the cylinder. If you hit the brake hard, then the rubber cup expands with some force creating a good seal. But light brake pressure and the MC doesn't catch, or slowly bleeds off pressure internally (thus no external leaks) Having grown up poor, it was not uncommon to have a car that required an occasionaly double pump to stop. Quote Link to comment Share on other sites More sharing options...
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