howardjm

First of all I am a first time Corvette owner and am trying to do all work myself, this forum has gave me excellant advice and appreciate all the input. Now I have another problem on my 89 Coupe. Here are the sequence of events prior to installing new front pads.
1. I pulled the wheels and pressure washed the front suspension
2. Replaced front shocks
3. Installed new brake pads
4. after I installed the pads I started the vehicle and pumped the brakes.

Now the brake pedal takes excessive force to stop the vehicle. I also here a air noise when I apply the brake. At higher speeds It feels like the stopping is normal, however at lower speeds I have to push hard on the pedal. I did not, as far as I know get air in the system, meaning I did not open a brake line or let the master cylinder get low, I have no leaks and the Master cylinder is topped off. Do I need to bleed the brakes? I did not hear the air sound prior to any of this. Please help!

eutu1984

Check for sucking noise near brake booster when car is running. If its leaking that may be your problem.

c4cruiser

A leak in the vacuum hose from the back of the manifold to the brake booster could be the problem, but it's also possible that the booster itself has gone bad. A hard pedal when stopping is usually indicative of a failed booster.

By chance, did you aim the pressure washer at the booster? The force of the stream of water could have been enough to loosen the hose at the booster or even cause the hose nipple on the booster to come loose.

howardjm

I did not spray the booster at all. Everything was ok prior to me doing the mentioned steps. Would the booster go bad just sitting there?

jhimer

Check for leaks in vacuum hose from TB to check valve on booster.

Check booster check valve. Should only have air move in one direction.

Plug vacuum hose at booster and drive car if same hard stopping=Bad Booster.

Good luck,
John

howardjm

if i take off the vacuum hose from the booster which way does the air flow in or out? The air sound i hear is in the car, i can not hear the sound at the booster

TTA579

Oh yes. The brake booster will fail all on it's very own. Do some vacuum testing on the booster and measure vacuum delivered to the booster.

It's a simple replacement, only a couple of bolts and no need to bleed lines. It's just a pain to get to nuts on the backside.

jhimer

Vacuum is drawn from the manifold through the brake booster vacuum hose to the check valve on the brake booster. Vacuum is pulled towards the manifold by the engine. The check valve can be removed by pulling and twisting from the booster.

The air sound in the car is probably a bad diaphragm inside of the booster.

howardjm

Do i keep the existing fluid in the master cylinder? are there bolts under the dash

TTA579

You'll want to test the booster first. It's not a cheap thing to replace. $100+?

IF you've determined the booster to be at fault, there are two nuts holding the brake master cylinder to the booster. Remove these nuts and gently push the master cylinder out of the way. Don't empty it, or undo any of the brake lines attached. You can even leave the sensor plugged in. Inside the car you'll need to do some yoga to reach the nuts that hold the booster to the firewall, removing the plunger from the pedal isn't so hard, getting it back on is the trick.

If you need more help, brake boosters share a common general design making youtube videos on the subject are pretty universal.