Mechanics

91 D21 PICKUP LEAKING FROM BEHIND THE MASTER CYLINDER

1991 Nissan Hardbody • 6 cylinder 2WD Automatic •

I own a 91 D21 Nissan Hardbody Pickup with about 173 thousand miles on it. The whole front disc brake, calipers and other parts were replaced about two months ago and then the rear drum pads and wheel cylinders were replaced about one month later (over the thanksgiving holiday.). A local brake shop did the front brake and I did the back myself.
Shortly after having the whole front brake assembly redone I noticed small puddles of what I discovered was brake fluid appearing right behind my front driver's side wheel well. I did a little investigating and found the source to be between the back (facing the firewall) of the master cylinder and the housing for the brake boots (I don't know what it is technically called). Anyways I was about to call the place where I had my front brakes done fixed then the spots stopped showing up and the leak stopped.
The leaking never started back up when I fixed the rear wheel cylinders and brake pads and I went back to school (I am a college student) with no apparent problems. I was home for about a week and it leaked one night. Then I drove it about 2.5 hours and let it sit for two nights. It didn't leak on the first night, but did after the second. The brakes are not spongy at all and I have had no problems stopping. I am just confused as to what would be causing the problem. It does not leak while driving and does not leak right after turning off the ignition. It has to sit for at least 4 hours before I see anything on the ground and it only leaks once and then won't again until after it is driven again. Any ideas and suggestions would be greatly appreciated. The truck is 2 wheel drive with the six cylinder (3.0L) VG30E engine in it.
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Ccrunner2289
January 7, 2011.




Sounds like rea seal leak. You could try replacing master cyl? That's enough miles to warant it.
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Tiny
Fixitmr
Jan 7, 2011.
Hello,

fixitmr, is correct about the seals. The seals in the master cylinder have failed and you will need to replace the master cylinder.

One other problem you may have is the brake fluid may have gotten into the Brake Power Booster, if this is so you may need to replace it also.

.

Obxautomedic
Jan 7, 2011.
Okay I will probably switch it out then. Any idea why it would only leak on occasion and never when it is on or right after the ignition is turned off?

Tiny
Ccrunner2289
Jan 7, 2011.
What, are you a scientist or something? Beleive me, cars can exhibit the freakiest symptoms and behavior that is just not consistantly explainable. Now if the new 1 leaks, then we got a mystery to solve.

Tiny
Fixitmr
Jan 7, 2011.
What, are you a scientist or something? Lol Take your advises and replace the brake master cylinder and move on-

Rasmataz
Jan 7, 2011.
I am going to school to be a Veterinarian so my brain is science based. I just figured I would ask, I'll replace the master cylinder and check the power brake booster and I'll go from there. Not what I wanted to do in 0 degree weather in Illinois but it's gotta get done.

Tiny
Ccrunner2289
Jan 7, 2011.
I wouldn't worry about the booster as you can change that in warmer weather if necessary. And i'm an old fart so I keep a spare car for winter just for such instances. My brothers classic TR7 just started leaking oil from his waterpump so he might be borrowing it!

Tiny
Fixitmr
Jan 8, 2011.
And if the leak aint terrible you could just add some fluid when necessary and wait for a 'nice' winter day to do the work? And you know sometimes you can change the master without any bleeding of wheels required!

Tiny
Fixitmr
Jan 8, 2011.
Just make sure you benchbleed the new master cyl.

Madmike1735
Feb 14, 2011.

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