brake problems (1 Viewer)

Joined
Jun 24, 2005
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29
 
I think my brake booster is bad. But after checking the price on a new one I want to be absolutely sure that its really the booster and not something else. Brake boosters for these vehicles are not cheap by any means from what I have found.
At times the pedal goes all the way to the floor with little or no resistance. I've noticed when I really stomp on it I'll get good pedal. Pumping it a few times seems to help,but does not seem as effective as just really stomping on it hard. It also idles low after it sits, then you go and drive around for a few minutes and it will idle back up to where its suppose to be. Even when she is up to operating temperature and I shut it off then restart it after just a few minutes it idles way to low. Does anybody have any idea on anything else it could possibly be besides the booster? thanks.
 

2mbb

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Sep 1, 2003
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WC, CA
 
 
 
There's a procedure for checking the booster in the FSM (see below). Also the troubleshooting section lists two symptoms that could be a bad booster: grabbing/chattering brakes and hard, ineffective pedal. These do not seem like the symptoms you are describing. A leaking booster, or low vacuum to the booster would make the pedal really hard and the truck hard to stop. The booster essentially helps you push on the pedal, but doesn't effect the hydraulics. If your pedal goes to the floor, it's probably the master cylinder or something wrong with the hydralics: air in the line, seals, etc
brake booster test.JPG
 

60wag

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Jun 25, 2003
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Boulder, CO
 
 
 
Usually when boosters go bad, the pedal gets hard. When the pedal goes to the floor its a bad master cylinder. Its possible that both are bad but I'll bet the idle problem is a vacuum leak. The booster could be the leak but I would expect the idle to change when you press the brake pedal. Put a vacuum gauge on it to see what vac the engine is creating. If it decreases when the engine warms up, I'll bet its either the intake manifold or carb base leaking.
 
Joined
May 19, 2005
Messages
686
 
 
 
I had very similar symptoms and it was the M/C.
BTW I believe the FJ80 M/C is and exact match except it has larger pistons, which would be perfect if you ever upgraded to 4Runner calipers!
Toad
 
Joined
Jun 24, 2005
Messages
29
 
Thanks for the help, I am going to get a new master cylinder and see if that fixes the braking problem. I have a vac gauge hooked up in the cab and it reads 18 at idle, which I think is pretty good. At times though, the needle won't be rock solid and flickers right around 18. Is this normal or should it be completely steady at all times at idle?
 
Joined
Mar 29, 2006
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AZ
Did a new M/C sovle the problem? if so which one did you go with stock or larger one from an 80?
 

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