Power Brake Booster – Chevy Silverado 1989

You’ll know the power brake booster is bad when you start to see fluid leaking from the weep hole underneath it. For what it does, the power brake booster is a hearty beast! Replacing a few “O” rings and it will work like new again.

Keep in mind that there are two very, very, different brake boosters for these Chevrolet trucks. There is a power brake booster used on the 1500’s and the 2500’s, but the 3500’s use a hydraulic power brake booster. These are totally different.

The regular power brake booster can be found just about anywhere you look! The hydraulic power brake booster can prove to be a bit more difficult to come by. I couldn’t order one from any of the auto parts stores. One place could get it, a week later. The others simply had no access to the part. I ordered the rebuild kit, much easier and faster to get ahold of. Be careful if you decide to buy the hydraulic brake booster because prices vary greatly. I saw everything from $99 to $900. Yes, some were $900. So, shop around for the few that are available.

I would rate this repair as moderate. I don’t think an amateur should take it on, but you don’t have to be a pro to do this repair/rebuild. Let’s take it step-by-step…

Signs The Booster Was Bad

I noticed fluid dripping from the weep hole a while ago. I don’t drive the truck very often so I let it go for a little while, and a little while more and a little while more, until, one day, the fluid was pouring out and the brakes were making a wailing noise and they didn’t work right anymore. The noise itself was awful and stepping on the brake just made it worse while thumping to a stop with all my weight on the brake pedal. So, I dove in to rebuilding the power brake booster. Here’s how it went.

At first I intended on just buying a new rebuilt brake booster, but once I saw how ridiculous they cost I went for the rebuild kit. I ordered it on Ebay and it arrived in just a couple of days. The booster came with a typed message to get the instructions on a specific page online which I did. The instructions were not the best. I was expecting something with better detail. Some of the items described in the instructions were not lableed on the photo of the instructions. Thankfully the brake booster is a fairly straight-forward piece of equipment.


Order the rebuild kit before doing anything.

There were two pieces that were not included in the rebuild kit that I was terribly disappointed about. The retaining star, with the attached grommet, as pictured above, was not in the rebuild kit and the washer, pictured below, was not.

This is an important part of the booster brake and it was not in the rebuild kit.

Regardless of these two components missing from the rebuild kit, I pushed on anyways. I would figure something out later.


When you have your rebuild kit in hand it’s time to get down to business and remove the power brake booster. In order to do this detach the master brake cylinder from the brake booster. This can be accomplished without removing the brake fluid lines from the master cylinder. There are two bolts holding the master cylinder to the brake booster. After removing the bolts I hung the master brake cylinder to the side with a bungee.


Remove the high pressure fluid lines and the return line from the booster.


To remove the brake booster from the firewall you will need to access the inside of the vehicle. The bolts are located down by the brake pedal. It can be a difficult area to access. I push the drivers seat back as far as it will go, then I lay down on my back, on the floor of the truck, and prop my feet up on the open window of the door. Now follow the brake up the bar to where it meets the firewall. There are four screws surrounding it that need to be removed to get the brake booster out.

Where the booster rod attaches to the brake lever remove the attachment. It’s a clip that slides up, yours may slide sideways, and then the rod can be slid off the lever.

Once the bolts are removed go back under the hood and remove the brake booster, it will just slide out. Try not to rip up the threads on the bolts as you slide it out.

And there you have your brake booster.


Now that the brake booster is out, you can start replacing the parts by removing the star retaining washer. There is a spring behind this star washer, so expect pressure when you press in on the star washer to remove it. Personally, I covered the brake booster with an old shirt when I removed the star washer because I didn’t want to risk the spring shooting it across the room.

Then I removed the bolts holding the booster together. Again, using caution so parts didn’t fall out unexpectedly.

One part of the instructions I decided not to follow was removal of the rod from the booster. It is a bit of a challenge to remove the rod and I don’t feel it was necessary. I found I was able to slide the two new “O” rings over and down the rod without a problem.

Open the booster carefully paying attention to how the piston is attached to the rod. Slide it out and start replacing the seals and “O” rings.

When you’re done replacing the seals and “O” rings place the new figure 8 seal into it’s groove and carefully slide the piston back in and replace the bolts that hold it together.

When it came to that yellow washer that wasn’t in the rebuild kit I had to do something because it was an important part of the booster that was clearly broken. So, I decided to make the seal. Using an old gas filter I cut off the end of it. Shaped it like the old seal and put it into the booster. It fit just fine.

You’re done rebuilding the cylinder.

Button It Up…

Now you can put your spring in and press the star washer on top of it and attach it to the lip of the inside of the cylinder.

Reinstall the brake booster, being careful not to strip the threads of the bolts as you slide it into place on the firewall. Torque the bolts inside to specification, and re-attach the brake booster brake rod to the brake pedal.

Bolt the master brake cylinder onto the brake booster and attach the lines back to where you had removed them from the brake booster.

Bleed The System

Fill the power steering reservoir and bleed the system by:

  1. Lift the front end of the truck onto jack stands.
  2. Turn the engine over a few times without starting the engine.
  3. Check the power steering fluid level.
  4. Check the booster for any leaking.
  5. Turn the engine on and turn the steering wheel from right stop all the way to left stop. DON’T push hard on the right and left stops. It’s just a gentle turn all the way to the right and a gentle turn all the way to the left.
  6. Check the power steering fluid, top off as needed.
  7. If the fluid is foamy, let the truck sit for about an hour and start over at step #2.

Continue turning the wheel from left stop to right stop and checking the fluid level until you no longer have to add fluid. Then you can put the truck on the ground and go for a test drive. Check the power steering fluid once-in-a-while during the first couple of days as trapped bubbles may come out and the power steering fluid will need to be topped off.

You’re Done!

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