1992 nissan d21se truck

[croomes7228]

I hope someone out there can help me.heres the problem once I drive for a few minutes my brake petal becomes harder and harder and after a couple of minutes I can let off the gas and the truck will come to a stop and even lock up.I have changed the master cyclinder, booster, rubber lines and even took brake lines off one by one and blew them out.still same problem.the master cyclinder and booster was both used so I guess one could be bad.but I don't think so.both of them do thesame thing.old one and the one I replaced it with.please help.thanks

[Pento240sx]

That sounds like your calipers are sticking. That's more likely your problem.

[Ace2cool]

Sounds exactly like the problem my motorcycle was having when I swapped the brake lever and didn't line the actuator rod back up into the hole on the lever it was supposed to go into. Basically what was happening was it was applying force to stop, but wasn't allowing the rod to travel far enough back in order to have the fluid feed back into the reservoir and relieve pressure in the lines.

What I suggest doing is going up under the dash, and loosening the lock nut on the bolt that connects the pedal to the master cylinder and backing it out some, then tightening the lock nut and taking it for a test drive. If it still locks up, then loosen some more. If you run out of bolt, then you most likely have another bad master cylinder.