DanStew

I recently changed the Brake MC. The 4runner stops fine, BUT it feels like it is manual brakes. I would expect the 4runner with a power booster would let me stop a bit better. So i want to check out the booster. Unlike other vehicles, i can have my foot on the brake, and start the truck and never feel any pressurization of the pedal. I have fine and firm brake pedal but just think there shouldbe a little more help. As searching throguh the posts, there was one post about removing the hose fro mthe booster and cap it off. And press on the brakes to see if the engine dies. I do not understand why this would help since the hose is capped off and there would be no vacuum leak to cause the engine to idle down. So i am looknig for any other ways to test the brake booster. It is not like i am in danger but my right leg is starting to get a little more stronger than the left leg.

tHanks

rustypigeon

Here is how to test the brake booster, straight from the FSM....
1. With engine off, depress petal several times. The clearance from the petal to the floor should not change if the engine has not been run recently.
2. Start the engine with your foot pushing the petal. The petal should go down slightly.
3. Run the engine for a couple minutes. Shut the engine off and press the petal several times. The petal should go down furthest the first time, then gradually rise with subsequent presses. This indicates that the booster is airtight.
4. Press the petal with engine running, and stop the engine with the petal depressed. If the petal does not move after 30 seconds, the booster is airtight.

84sr5yoty

Remove the vacuum line from the plenum (or carb if so equipt) and create a vacuum with a vacuum pump (I just suck on the hose and put my tongue over it to hold vacuum). It should hold perfect vacuum indefinitely.

Using this method, you are checking the vacuum line, check valve, and brake booster for any leaks.