TSleid

So i have a 1991 240sx and after a while of driving and the odd time right away the brakes start applying by themselves and wont let off therefore causing a massive drag. I pull over when this happens and pump the pedal a bunch of times until the pedal goes back to normal and then its fine till the problem occurs again after a bit.

Back Calipers have been replaced and everything visually seems fine. So i figured its the brake booster not letting pressure release so when the problem occured again yesterday i got out with the car in neutral and ebrake down and tried pushing the car and it wouldn't budge. So i then went under the hood and pulled the vaccumm line off to the booster to purge the air and then put it back on quickly and then pushed the car and it started rolling like normal.

So i'm assuming that's a sign that the booster or MC is pooched?

Any help with this is much appreciated.

Thanks

KendallH

Check your pedal too. On my old s13 the first day I got it same thing happened. After replacing all calipers and master, someone told me to check my pedal. Turns out someone had rigged the brake light switch in a way that was holding just enough pressure on the pedal to cause the calipers to heat up and lock. Turns out this is somewhat common as the small plastic piece that usually engages the brake light switch usually breaks off and people replace it with whatever they have, usually a bolt. With the car off, slowly push in the pedal. You should feel some "play" area before you feel it hit the master cylinder. If not, get under there and see whats in the pedal where the brake light switch is. Hope this helps.

TSleid

Alright thanks very much. I'll definately check that out before ripping things apart.

Zach-sr

I had this exact same problem. Me and my friend went through and replaced EVERYTHING.... Booster, Master cylinder and all calipers. Turns out the hoses that go to the calipers swell up when they get hot which causes more pressure, when they are older. I put a set of agency power lines on and fixed it.
After I bought these I relized chase bays has a cheeper set.
Chase Bays Fenderwell Brake Lines - Nissan 240sx S13/S14 - Nissan 240sx - ChaseBays.com

When the brakes do this the pedal is hard as a rock right?

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TSleid

Yeah exactly, its hard as a damn rock like i can push it maybe a few mm but thats it and it's not depressed.

But Oh okay that makes sense. I never even thought of that. I just looked to see if they were leaking but that's great advice. I might just do that. THANKS!

Edwin562

i have same damn problem..... only thing left for me is the booster or the MBC...