How to Fix Rochester Quadrajet Vacuum Leaks

Remove the air filter and filter housing from the carburetor. Plug any hoses disconnected from the housing. Use a sharp pencil or golf tees to plug vacuum lines of various sizes. Replace a damaged or missing gasket that seals the filter housing to the carburetor. Overtightening the filter wingnut to compensate for a worn or missing gasket can distort the body of the carburetor and create a vacuum leak.

Start the engine to check the choke pull-off for leakage. The vacuum-operated pull-off is at the passenger side rear of the carburetor. Remove the vacuum hose from the pull-off to check the vacuum supply at the hose. Place your thumb over the end of the hose to feel the vacuum strength and prevent engine stalling. Connect the hose to monitor pull-off motion. Replace the pull-off if no motion occurs when vacuum is applied.

Remove the hose from the float bowl vent nipple and place your thumb over the end of the hose. Replace the charcoal canister control valve if any vacuum is felt in the hose with the engine running. Check crankcase vent valve function by removing it from the rubber grommet and blocking it off with your thumb. A light click noise should be followed by a slight reduction in engine speed. Make sure vacuum supply is sufficient before condemning the valve.

Remove each vacuum hose at both ends to make a thourough inspection. Replace any vacuum hoses that appear cracked or damaged in any way. Rubber vacuum hoses can rot on the inside with no outer visual deformities. Replace any vacuum hose that caves in when vacuum is applied or fits loosely at either nipple. Inspect and replace one hose at a time to avoid crossed connections.

Pinpoint leaks using aerosol carburetor and choke cleaner. Attach the thin red pipette provided with the product to the aerosol can nozzle. Closely direct a one-second blast of cleaner at the driver's side of the primary throttle shaft. Install a throttle shaft bushing kit if engine speed increases noticeably. Use quick, light sprays to check the carburetor base gasket for leaks. Replace the base gasket if it draws in any cleaner and engine speed increases.