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Mopar Certified
Mopar Certified, Dodge Technician
Category: Dodge
Satisfied Customers: 11332
Experience:  24 Year Chrysler/Dodge Certified Specialist
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My front brakes keep locking..master cylinder..slipping..pedal

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my front brakes keep locking up, and I removed the check valve and replaced it, pull the master cylinder, and still could not manually rotate the front wheels, so i figured it to be the brake lines and just replaced those, and bled the whole system, and went for a five minute ride, all of a sudden it felt as tho I had alignment issues, shaking and then it felt as tho the transmission was slipping and then the brakes engaged and I came to a full stop ,smelled burning and could not get the truck to advance, to the point that I opened the brake bleeders to relieve pressure and left the check valve off with a piece of paper over the valve opening to get home. The pedal is very high and hard to depress if for an inch at that. Any suggestions, I was thinking a bad booster? thanks alot .


Here is one test you can do on the booster.


With the engine off, pump the pedal numerous times. Then, with your foot firmly pushing on the pedal, start the engine. The vacuum from the running engine should cause the brake pedal to drop about an inch or two.


If there is no drop, then the booster is faulty.

Customer: replied 7 years ago.
with the engine off you cannot pump the pedal it is hard as a rock you have to put a ton of force to pump it it barely moves, thank you for your time

Ok, does it drop at all when the engine is started?


If it doesn't then the booster is faulty.

Customer: replied 7 years ago.
ok first thanks sorry about the delay my baby woke, so I went out and mind you the truck is cold now sitting for a half hour so I can pump the brakes cold again and then while pushing i started the engine and it dropped about and inch, but I had that before when the truck was cold until i drove it a bit and then again problems.

Ok, if the problem is not occurring right now, you'll need to duplicate the problem and then re-try that procedure.



Customer: replied 7 years ago.

yeah they are hard again and we have vacuum but it doesnt release that vacuum, I had explained that once I removed the check valve and covered the check valve with a card, essentially removing the booster I was able to drive it again with limited braking. Are we leaning towards the booster? I duplicated the whole thing and could pump it very little and then while holding it start the engine and it drops ever so slightly, but then I drive for a bit and it locks again as if not pressure relief, just to say again thanks alot for the help.



Yes, this is very much indicative of a failed booster and personally, I would just be changing it because it has all the makings of a booster issue.


There is only one test for the booster and that is the procedure I told you about.

Customer: replied 7 years ago.

THANK YOU VERY MUCH IT IS MUCH APPRECIATED ordered a booster and will get it monday, thanks




You're more than welcome.
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