the brake pedal, the engine..rough

Vacuum Booster

REMOVAL & INSTALLATION:

REMOVAL & INSTALLATION

See Figure 1

1. Disconnect the negative battery cable.
2. Apply the parking brake.
3. Unplug all necessary electrical connections.
4. Remove the master cylinder from the booster and pull it off the studs, CAREFULLY! It is not necessary to disconnect the brake lines.
5. Disconnect the vacuum hose from the check valve.
6. If necessary, remove the brake light switch.
7. Disconnect the booster pushrod at the brake pedal.
8. Remove the booster mounting nuts, located on the inside of the firewall.

 

Fig. Fig. 1: Vacuum booster mounting

1. Lift off the booster and remove the gasket.

To install:

1. Install the booster with a new gasket.
2. Tighten the booster mounting nuts to 21 ft. lbs. (29 Nm) on all except 1996-98 models. On 1996-98 models, tighten the nuts to 26 ft. lbs. (36 Nm).
3. Install all remaining components.

http://www.au tozone.com/autozone/catalog/parts/partsShelf.jsp?categoryDisplayName=Brakes+%26+Traction+Control&fromType=parts&fromString=search&parentId=44-0¤tPage=1&filterByKeyWord=brake+booster&isSearchByPartNumber=false&navValue=14400143&categoryNValue=14499999&fromWhere=&itemId=143-0&displayName=Brake+Power+Booster&searchText=brake+booster

Brake Power Booster

Showing 1 - 2 of 2 Items
Sort by Price:  High  Low --- Select a Brand --- Cardone Reman Cardone Reman / Brake Power Booster Part Number:
54-71085   Price: $125.99
Core*Core value is the used part that manufacturers use for rebuilding. AutoZone charges the core value to customers because manufacturers include it in their prices. When you return your core to AutoZone, we'll refund your core charge.: $28.00
Total: $153.99 Application:
With JB5, JB6 and JB7 brake system
Warranty:
LLT Notes: W/o master cylinder
STORE PICK UP IN STOCK SHIP TO HOME AVAILABLE  Cardone Reman / Brake Power Booster Part Number:
52-7358   Price: $176.99
Core*Core value is the used part that manufacturers use for rebuilding. AutoZone charges the core value to customers because manufacturers include it in their prices. When you return your core to AutoZone, we'll refund your core charge.: $46.00
Total: $222.99 Application:
With JB8 brake system
Warranty:

when you press on brake pedal the idle goes way down and you can hear air

I have a 1985 chevette when you press on brake pedal the idle goes way down and you can hear air. But the air leak is not coming from the brake pedal. It has standard brakes

The brake booster operates on a vacuum created by the engine. There is a thick wall hose connecting the inlet manifold to the booster. The booster has a non return valve in it which allows a couple of pumps of the pedal in the event of the engine stalling. This should allow you to bring the car to a safe stop. You don't say if the brake pedal feels normal but the change in idle is caused by you operating the booster. My guess is that the air noise you can hear is a leak in the hose or the booster itself. This may require the assistance of a good DIY mechanic to determine which it is. Make sure you get the correct thick wall hose if its that, that is faulty, because any normal hose will be sucked flat by the vacuum and you will have no brakes!! Should the hose be OK and the booster be the noise you can hear then replacement is the only option. A quick call to a parts house with the vehicle details will soon tell you. If you think about it your car is 30 years old, pretty good going really.

It looks like the brake power booster is defective. A vacuum problem. You say it has standard breaks. Then the brake pedal lever is somehow interrupting a vacuum hose.

Some part of the brake linkage must be pressing on a vacuum hose. Check under dash as well as under hood.