Brake hydro booster leak?

BILL MARSHALL

MEMBER
2004 CHEVROLET TAHOE
5.3L
V8
4WD
AUTOMATIC
155,000 MILES

I've noticed that it seems to be wet around and below the booster. I know this particular design serves as the power steering pump as well as the brake booster but, both fluids are pretty much full. From underneath (laying under the truck, looking up) I can see drops collecting at certain points (see pics). Some things I've read say the booster is serviceable and others say only the dealer can service it. I'm assuming it's just a couple of seals, is this something I can tackle myself? I do just about all of my own repairs on my vehicles but, I've never dealt with the hydro booster before. Any tips or suggestions would be greatly appreciated. Thanks

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3 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,602 POSTS

Yep, it looks like the hydro booster is leaking, I have never put seal in one of these, but I do know there is an accumulator that can have stored pressure so be careful of that, in the shop we would install a rebuilt unit. Here is hot to change it out:

Apply the park brake and block the wheels.
Depress brake pedal at least 10 times in order to relieve pressure in the accumulator.
Remove the master cylinder from the hydraulic booster. Refer to Master Cylinder Replacement.

Place the J 26889 over the end of the accumulator. See Special Tools and Equipment.

Install the nut on the stud.
Depress the accumulator with a C-clamp. If the accumulator does not move with moderate pressure, remove the C-clamp and depress the brake pedal ten times in order to relieve pressure in the accumulator.

Install the gasket.
Install the booster assembly.
Install the 4 booster to bulkhead nuts.
NOTE: Refer to Fastener Notice in Cautions and Notices.
Tighten: Tighten the nuts to 33 N.M (24 lb ft).

Fig 11: View Of Hydraulic Brake Booster Assembly, Nuts & Gasket
GM361376
Courtesy of GENERAL MOTORS CORP.

Install the stop lamp switch. Refer to Stop Lamp Switch Replacement in Lighting Systems.
Install the master cylinder. Refer to Master Cylinder Replacement.
Connect the return hose, the steering gear, and the inlet hoses.
Bleed the hydraulic booster system. Refer to Bleeding the Power Steering System in Power Steering System.

Release the park brake and unblock the wheels.
Power Brake Booster Outlet Hose Replacement
Removal Procedure

Install a drain pan under the vehicle.
NOTE: Refer to Power Steering Hose Disconnected Notice in Cautions and Notices.
Fig 12: View Of Power Brake Booster Outlet Hose
GM650861
Courtesy of GENERAL MOTORS CORP.

Remove the brake booster outlet hose (1) from the brake booster (2).
Remove the clamp retaining the brake booster outlet hose to the power steering pump.
Remove the brake booster outlet hose from the vehicle.

Installation Procedure

Route the hose in the same position the hose occupied prior to removal.
Fig 13: View Of Power Brake Booster Outlet Hose
GM650861
Courtesy of GENERAL MOTORS CORP.

NOTE: The inlet and outlet hoses must not be twisted during installation. Do not bend or distort the inlet or outlet hoses to make installation easier. Failure to follow these procedures could result in component damage.
Install the brake booster outlet hose (1) to the brake booster (2).
Position the clamp at the end of the hose.

Install the brake booster outlet hose to the power steering pump (4).
Position the clamp at the end of the hose.

Remove the drain pan from under the vehicle.
Bleed the power steering system. Refer to Bleeding the Power Steering System.

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