OVERVIEW
Genuine VW/Audi coolant temperature sensor O-ring, part number N-903-168-02. This original sealing ring closes the connection between the assigned clip-in coolant temperature sensor and its coolant flange or hose housing. It is supplied individually for sensor replacement or repair of a diagnosed leak at the sealing connection.
Technical details
- Original number: N-903-168-02 / N90316802.
- Published nominal dimensions: 19.6 x 3.6 mm.
- Application: specified clip-in coolant temperature sensor sealing position.
- One O-ring supplied. Sensor, retaining clip, coolant flange, hoses and coolant are separate.
The O-ring forms the fluid seal around the sensor's mounting connection. The separately specified retaining clip locates and retains the sensor; the ring does not replace that clip. Correct seal size and an undamaged housing are essential to a sound cooling-system connection.
Cooling assemblies can contain several similar-looking seals. Match the original ring number and the actual sensor arrangement rather than selecting by vehicle model alone. This ring is not a thermostat gasket, water pump seal or general-purpose substitute for other cooling connections.
Common reasons to replace
Renew the seal during sensor replacement when required by the applicable procedure. Replace a cut, flattened, hardened, swollen or otherwise damaged ring, or a ring that no longer seats correctly in its assigned connection.
Coolant residue or a diagnosed leak around the sensor can indicate a sealing problem. Inspect the sensor seating area, retaining clip, flange and nearby hoses to establish the actual source before ordering repair parts.
Previous installation can pinch the ring or leave an incorrect seal in place. Replace unsuitable or damaged sealing hardware and inspect the housing for damage before refitting the sensor.
A new O-ring cannot repair a cracked coolant flange, damaged sensor housing, missing retaining clip or a leak from an adjacent hose. Temperature readings and fault codes also require diagnosis of the sensor and electrical circuit; replacing the ring alone does not correct an electrical defect.
Installation and service notes
Follow the factory procedure for the exact coolant sensor arrangement. Allow the system to cool and release pressure as prescribed before opening the connection. Collect coolant using the required service method.
Remove the sensor and old seal carefully. Inspect the sensor sealing area and housing bore, and remove old seal material or debris without damaging the contact surfaces. Correct a cracked or distorted housing before installing a new ring.
Fit the prescribed seal in the proper position. Use only the installation preparation specified by the procedure, and avoid twisting, cutting or pinching the ring as the sensor enters the housing.
Seat the sensor fully and install the correctly specified retaining clip. Do not force the clip into a partially seated connection or use the retaining hardware to compensate for an incorrect seal. Check the clip, sensor and housing engagement before refilling.
Restore the cooling system using the specified coolant and filling or bleeding procedure. Do not infer coolant type or fill quantity from the O-ring number. Select fluid and other cooling service components separately for the vehicle.
Complete the prescribed leakage and operating-temperature checks after service. If seepage remains, inspect the sensor seating, seal condition, clip engagement and housing before continuing operation. This listing supplies one original O-ring.
Fitment
| Vehicle | Model years | Engine | Configuration | Application restrictions |
|---|---|---|---|---|
| Audi S4 | 2000–2002 | 2.7L twin-turbocharged gasoline V6, APB | B5 sedan, quattro; 6-speed manual | Original clip-in coolant temperature sensor sealing position requiring N90316802. Confirm sensor, coolant flange and original seal number; other cooling seals differ. |
| Audi S4 Avant | 2001–2002 | 2.7L twin-turbocharged gasoline V6, APB | B5 wagon, quattro; 6-speed manual | Original clip-in coolant temperature sensor sealing position requiring N90316802. Confirm sensor, coolant flange and original seal number; other cooling seals differ. |
Confirm original N90316802 at the actual coolant temperature sensor sealing position before ordering. One O-ring supplied.