OVERVIEW
Genuine VW/Audi thermostat housing bolt, part number N-909-450-02. This original fastener secures the FSI thermostat housing to the engine at its assigned mounting position on the configurations below. One bolt is supplied.
Technical details
- Original number: N-909-450-02 / N90945002.
- Published nominal size: M7 x 21.5.
- Combined external hex and internal hex drive with a flanged head.
- Application: specified thermostat housing-to-engine attachment on the BPY FSI cooling arrangement.
- Thermostat housing, seals, hoses and other bolts are separate.
The housing fasteners hold the thermostat assembly at the engine connection while the specified seals retain coolant. Correct bolt length and seating are necessary for the designed attachment. Other fasteners in the same assembly can have different lengths; match the part number and position before ordering.
This is mounting hardware. It does not regulate coolant temperature or replace the thermostat's sealing components. The FSI attachment differs from the thermostat-to-water-pump arrangement used on TSI engines, so engine identification matters even when the vehicle model is the same.
Common reasons to replace
Inspect the bolt during thermostat housing removal, replacement or seal service. Replace missing hardware, stripped threads, rounded drive surfaces, deformation or corrosion that prevents proper installation. Follow any factory requirement to renew removed fasteners.
Previous cooling system repairs can leave a mismatched length or a damaged bolt. Check the full mounting arrangement before assembly. A fastener that bottoms out before the housing seats cannot establish the intended connection.
Coolant loss, slow warm-up or abnormal operating temperature requires diagnosis of the cooling system. A new bolt cannot repair a cracked housing, failed thermostat, damaged seal, stripped mating threads or a leak elsewhere in the circuit. Replace or repair the diagnosed component as required.
Installation and service notes
Follow the factory thermostat procedure for the BPY engine and exact cooling arrangement. Allow the engine to cool before opening the system, then perform the prescribed coolant draining and access steps. Keep contamination out of open coolant connections.
Identify the assigned housing-to-engine position and compare the removed bolt with N90945002. Inspect the housing, mounting surfaces and mating threads. Select the specified sealing components separately and install them according to the repair procedure.
Position the housing correctly and start the bolt by hand in undamaged threads. Do not use a fastener to draw a misaligned housing into place or overcome resistance from an incorrectly seated seal. Check that each mounting position receives its prescribed bolt.
Use the correct tool for the combined hex head and follow the factory tightening sequence and requirement for this attachment. Observe the prescribed thread preparation and replacement instructions. Do not transfer a torque value from another M7 bolt or a different thermostat design.
If the bolt does not seat normally, check the selected length, thread engagement and housing alignment before continuing. Additional force does not repair damaged threads or correct an incorrectly installed housing.
Refill with the specified coolant and perform the required bleeding, operating-temperature and leak checks. Confirm normal system operation after service. This listing supplies one original bolt; obtain the housing, seals and remaining cooling service components separately.
Fitment
| Vehicle | Model years | Engine | Configuration | Application restrictions |
|---|---|---|---|---|
| Audi A3 | 2006–2008 | 2.0L turbocharged FSI gasoline, BPY only | 8P hatchback, front-wheel drive; 6-speed manual | BPY FSI thermostat housing-to-engine attachment requiring N90945002. Match the exact bolt position and housing. Not the TSI thermostat-to-water-pump fastener. |
| Audi A3 | 2006–2008 | 2.0L turbocharged FSI gasoline, BPY only | 8P hatchback, front-wheel drive; 6-speed DSG | BPY FSI thermostat housing-to-engine attachment requiring N90945002. Match the exact bolt position and housing. Not the TSI thermostat-to-water-pump fastener. |
Confirm BPY FSI engine and original N90945002 at the specified thermostat housing mounting position. One bolt supplied.