Removing and installing thermostat with housing: Audi A3 4.2 (BNS, BUJ, BYH, CEPA, …)
Step-by-step removing and installing thermostat with housing for the Audi A3 4.2: 16 steps. What to remove, in what order, and what to check after.
Workshop procedure for AUDI — the exact step sequence and torque figures, straight from real workshop data.
🧭 Before you start
Fits: Audi A3 (8P, 2003–2012)
- Opens: coolant
- Renewed: o-ring
Don't miss
- Ignore (items 2, 3, 4 and 5).
- Fit new O-ring.Secure all hose connections with the correct type of hose clips (same as original equipment) Electronic parts catalogue.
- Do not reuse coolant.
📋 Procedure
- Drain coolant .
- Remove radiator cowl .
- Pull out oil dipstick (2).
- Remove bolts (arrows) and lift off guide tube (1) for oil dipstick.
- Remove bolts (1 and 3).
- Release hose clip (2) and detach coolant hose.
- Remove air cleaner housing .
- Release hose clip (1) and detach coolant hose.
- Remove bolts and nut (arrows) and detach front coolant pipes from thermostat housing. [Note: Ignore (items 2, 3, 4 and 5).]
- Remove bolts (arrows) and detach thermostat housing. [Note: Fit new O-ring.Secure all hose connections with the correct type of hose clips (same as original equipment) Electronic parts catalogue.]
- Clean and smoothen sealing surface for O-ring.
- Lubricate O-ring with coolant.
- Install coolant pipes (front) .
- Install air cleaner housing .
- Secure dipstick guide tube . [Note: Do not reuse coolant.]
- Fill up with coolant .
Other AUDI procedures
- Checking fuel pump delivery rate - vehicles with 4-cylinder FSI engine
- Removing and installing auxiliary radiator (left-side) – Audi
- 8-cylinder direct petrol injection engine (4.2 ltr. 4-valve RS 4), mechanics — Securing engine to engine and gearbox support
- Removing and installing hose for crankcase breather system
- Checking combination valves for secondary air system for correct operation and leakage
- Removing and installing toothed belt – Audi · 56 torque figures
- Removing engine – Audi A8 D3 · 41 torque figures
- Removing camshaft timing chain from camshafts – Audi A6/A7 C7 · 38 torque figures
- Installing engine – Audi A8 D4 · 36 torque figures
- Removing and installing camshaft timing chain · 29 torque figures
Who makes these pages, and how
TorqFix was built by a mechanic — after a 2,700 km drive with five roadside repairs that no diagnostic tool could explain.
The figures on this page come from manufacturer workshop documentation and are shown as they are. The page is assembled automatically from that data — it is not written by an AI. The AI works in the chat, where it answers for your specific car. It writes nothing here.
Variants of the same model differ. Cross-check torque against the factory manual for your engine before final tightening.
Seen a figure that does not match your manual? Write to us — we correct it and note when. support@torqfix.com
The story behind TorqFix →Workshop data on this page last updated 20 Sep 2026.