Hard Brake Pedal

[dirtriderdd]

Brakes were working fine all day yesterday. Then immediately upon start-up for my drive home the brake pedal went hard. I have brakes but completely unassisted. I have vacuum coming off the engine to the booster, but I don't know exactly what pressure. The brake pedal does not compress when I turn on the engine. Leads me to think it is a bad booster. I changed the booster today, but still have a hard pedal and no assisted brakes. I thought for sure it was the booster. It's possible the new (refurbished) booster is bad, but unlikely. Any suggestions?

 

[smoothandlow84]

If you replaced the brake booster, did you also replace the brake booster check valve? Normally there is a "swoosh" sound made when the booster goes bad, followed by a hard pedal.

 

[chengny]

The brake pedal does not compress when I turn on the engine. Leads me to think it is a bad booster.

There are a couple more steps in addition to the one you mention above. See steps 5 & 6.


CHECK FOR PROPER BRAKE BOOSTER OPERATION

1. With the engine "OFF", depress and release the brake pedal 4-5 times.
2. Depress the brake pedal firmly and start the engine.
3. If the pedal goes down slightly the brake booster is operating properly.
4. If the pedal does not go down slightly the brake booster is not assisting in brake operation. Verify vacuum supply to the booster.
5. Maintain pressure on brake pedal while turning "OFF" engine. The pedal should remain in the same position. If the pedal slowly slowly rises, the booster or vacuum check valve is leaking. Replace as necessary.
6. Verify the brake booster vacuum line is intact and installed properly. Verify that the vacuum check valve allows flow only towards the intake manifold, and not in reverse towards the booster.
7. Verify that engine vacuum is at least 17 in hg.