Can't Stop!

OCMike

OCMike

New member
So today I was driving around, and all of a sudden, my brakes are very hard to press. I also noticed that my engine would bog down as I held the brakes. Luckily, I made it home, but the brakes got worse as I kept going. The brakes also made a sound like air escaping when I pressed them. The little bit of searching I did points to either the brake booster or master cylinder? Any thoughts?
 
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Probably a booster issue, given that it's affecting the engine, too. While I'm no brake guru, I believe any issue with the master cylinder (meaning fluid flow) would result in a soft pedal, whereas the booster is a vacuum issue.
 
That is definitely your brake booster.

The brake booster is vacuum actuated from engine vacuum pressure. When the engine bogs down when you press on the brakes, you basically have a vacuum leak. That air you're hearing is that vacuum leak. Also, the brake pedal is hard to press because you've lose the vacuum assisted brakes (brake booster).

Here's a definite way to test it. With the engine off, pump the brakes till the brake pedal is firm. Keep pressure on the brake pedal and start your engine. If the booster is good then your brake pedal will sink to the floor. If your booster is bad then your brake pedal won't move. Seeing as it sounds like your internal diaphragm inside of the booster is torn, your engine may not start (huge vacuum leak) or if it does start then it will run very rough.

My money is on your brake booster. They are about $80 at your local auto parts store. Keep your broken one because there is a core charge. I went through this about a year ago on my 4runner.
 
SV_Dude said:
That is definitely your brake booster.

Here's a definite way to test it. With the engine off, pump the brakes till the brake pedal is firm. Keep pressure on the brake pedal and start your engine. If the booster is good then your brake pedal will sink to the floor. If your booster is bad then your brake pedal won't move. Seeing as it sounds like your internal diaphragm inside of the booster is torn, your engine may not start (huge vacuum leak) or if it does start then it will run very rough.
Click to expand...

I went out and did your test. I was able to move the pedal, but it was very stiff. When I started it up, the engine ran rough and I could hear air escaping down near the pedal area.
Hoping it's just the booster. Seems like a pretty doable repair with the limited tools I own.
 
Swapping the booster is simple. It's isolated from the Master Cylinder, so there is no bleeding required. Just unbolt the MC from the booster, unbolt the booster, disconnect the pedal linkage inside.
 
if you replace your booster be sure to get a dual diaphragm booster off of a turbo or 3.0 motor. it is a nice big improvement in breaking power
 
opps. just noticed you already have a dual booster and 1inch mastercylinder just get your stock booster.






keep moving nothing to see here.:zoom:
 
Thanks everyone. I was thinking it might be the booster. Just needed others to confirm my thoughts. Now I just need to get down to the parts store and get this thing done.
 
smiley_git_r_done.gif~original
 
OK. So it was the brake booster. I was able to change it out in under 2 hours. The firewall bolts were a pain in the butt though.

So I have this new problem. The brake lights stay on when I let off the brakes. I know it's the switch, but how to I adjust it? The bolt looks like it's welded on.
 
Congrats on fixing the problem yourself.... How much did you pay for the Booster?

I have no idea about the light... I'll just wait for SV to chime in :)
 
I think I'm just so wore out from contorting my body under that dash that I don't have to strength to loosen the nut. LOL I'll give it the old college try again in a few minutes.
 
Improvising FTW! When all else fails, grab the tube of liquid nails and a piece of scrap plastic for a makeshift spacer.
 
Odds are that the light issue is your switch at the brake pedal. There is an adjustment either on the switch OR on the top of the brake pedal where it meets with the arm on the brake booster. One of these adjustments will change the angle of the brake pedal to move the pedal off of the switch and free play in the brake pedal.

See the FSM, there is a task in there for adjusting the pedal movement.
 
Thanks SV. I'll look it up. Right now, the plastic shim is almost working. If I get out of the truck and see the brake lights still on, I have to pull back on the pedal and they go out. I need to add another piece of plastic, or look in the FSM.
 
OOHH! So I just have to loosen the push rod nut and turn the push rod to adjust the pedal? That would be a lot easier than adding shims.
 
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