Brake Booster Problems?

Is there a real easy way to tell if my brake booster is weak? I dont have a vacuum gauge so I cant measure the vacuum, but is there another way? My brakes are real spongy and my mechanic said he thinks the brake booster is bad but he sucks at diagnostics. Thanks for any help.
Collin

If there was a leak or low vacuum, wouldn't the pedal be really hard to push and barely work - because of no assist? Actually, I have heard of a similar situation, but the vehicle was in really bad shape so there was not way to verify. Anyone ever disassembled a brake booster? Its kind of a black box.

I think since there is no assistance from the brake booster is the reason my brakes are so spongy. I mean I have to sink the pedal all the way to the floor. I think I've got a vacuum leak. I ran seafoam through it so that may have destroyed it.

The function of the Booster is to make it easier to push the brake pedal. Try stopping your car (not this one) when the engine is shut off - it will be hard to push the pedal. I'm not controdicting your mechanic on the Booster being bad - I have heard of this, but its rare. Here's what you should check, in order. Its long, but spongy pedal can be caused by lots of things (possibly even the booster).

Front brakes in good shape - pads are thick, rotors are smooth
Front brakes correctly assembled
Front brake calipers not hanging up on bracket
Unbolt front calipers and check for smooth piston movement

Rear brakes in good shape - pads are thick, drums are smooth
Rear brakes correctly assembled
Rear brakes are clean and correctly adjusted - should be slight drag (slight)

No leaks in system anywhere - No evidence of fluid leaking
Check all 4 wheels, Master Cylinder, lines, Proportion valve, under dash at rod connection
Check hoses for cracking or damage - replace
System has no air in it - Bleed and pump new fluid through
Pressure bleed brakes with pressure unit
Possible Master Cylinder leaking internally
MC will usually leak at the back, unbolt the two achor bolts and look

Hope this helps

My front brakes are more or less rebuilt and the back are as well. The drums are not the thickness they should be anymore so that could be a little of my problem, I guess. Other than that though, my brakes were just bled friday so I dont know what else it would be. I think its gotta be the booster.

JeepGuy: To check your booster, with engine off..pump brakes several times to get rid of residual vacuum. Then while holding the brake pedal down, start the engine. If booster is working you will feel the pedal drop. If your pedal is almost going all the way to the floor, it is usually adjustment or air in system. Don

jeepguy1990 said:

My front brakes are more or less rebuilt and the back are as well. The drums are not the thickness they should be anymore so that could be a little of my problem, I guess. Other than that though, my brakes were just bled friday so I dont know what else it would be. I think its gotta be the booster.

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When is the last time you adjusted the rear brakes? The automatic adjusters don't always work.

If the master cylinder has been leaking,there is a good chance that the booster diaphgram is history.
The composition of the diaphgram material does not play well with brake fluid.
Somebody asked if anybody had disassembled a booster,to do this it, is my understanding that there would be a buncha those "special, expensive, only use them on boosters, tools....$$$$$ It is recommended that you step away from the booster and let qualified people work on them..Or just go to your local parts store and get another w/LT warrenty............

Thats the same reason my mechanic gave me. Also he said my running seafoam down the booster probably killed the diaphragm as well. Its probably that thats killing my brakes but I did the test (rattler43) gave me to see if my booster was faulty and it did go down after I started the Jeep. What da heck?

My 90 xj had terrible brakes till I plumbed in a 96 booster.....saw the write-up
somewhere on this forum, but its not too hard to do. bigger booster and brakes are now great.....