Fuel Injector Seal O-Ring – 035-133-557 The 035-133-557 is a critical sealing O-ring designed for Bosch Continuous Injection Systems (CIS) found in various Audi and Volkswagen models. This specific seal fits onto the fuel injector body and creates an airtight connection when the injector is pressed into the injector bushing (035-133-554). Because CIS engines are highly sensitive to "unmetered air," a degraded O-ring here will cause significant performance issues, including a hunting idle and poor throttle response. Unlike standard rubber rings, the 035-133-557 is manufactured from fuel-resistant elastomers that withstand the high heat of the cylinder head. Over time, these seals become squared-off and hard, losing their ability to compress. Replacing them is a vital part of any fuel system refresh to ensure the engine receives the exact air-fuel mixture commanded by the fuel distributor. Detailed Vehicle Compatibility Audi 200: 1989, 1990, 1991 Audi 200 Quattro: 1989, 1990, 1991 Audi 4000: 1985, 1986, 1987 Audi 5000: 1985, 1986, 1987, 1988 Audi 5000 Quattro: 1986, 1987, 1988 Audi Coupe: 1985, 1986, 1987 VW Fox: 1987, 1988, 1989, 1990 Product Highlights & Features Airtight Vacuum Seal: Specifically sized to eliminate "false air" leaks at the injector base, which is the most common cause of lean-run conditions in CIS engines. Vibration Isolation: Helps cushion the injector within the bushing, reducing mechanical noise and wear on the injector tip. Direct OEM Fit: Produced to the original engineering dimensions for a snap-fit onto the injector body. Technical Specifications Part Number: 035-133-557 Component Type: Lower Injector O-Ring / Seal Material: Fuel-Resistant Elastomer System Type: Bosch CIS / CIS-E / CIS-Turbo Installation & Maintenance Tips Lubrication is Key: Before pressing the injector into the bushing, lightly coat the new 035-133-557 O-ring with clean engine oil or a tiny amount of silicone spray. This prevents the seal from tearing during installation. Simultaneous Replacement: It is highly recommended to replace the 035-133-554 bushing at the same time as this O-ring. A new seal in a cracked or old bushing will often still leak air. Check for Cracks: When removing the old injectors, inspect the injector body itself for pitting where the O-ring sits. The surface must be smooth for the new ring to seal correctly. Test with Propane: After installation, you can check your work by passing an unlit propane torch (valve open) around the injectors while the engine idles. If the RPM rises, the seal is not seated properly. 035133557
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