Parts for your 2016 Audi Q5-Radiator cap

2016 Audi Q5 radiator-cap: what it is, and why you won’t find one on the radiator

The 2016 Audi Q5 doesn’t use a traditional radiator cap on the radiator. Instead, it runs a sealed, pressurised cooling system that’s filled and vented via the coolant expansion tank (also called the reservoir) on the right-hand side of the engine bay under the bonnet. The pressure cap on that tank performs the job older “radiator caps” used to handle.

Technical sources back this up: the 2016 Audi Q5 Owner’s Manual identifies and shows the coolant expansion tank as the only fill and vent point, Audi’s erWin workshop documentation for the Q5 (8R) in Repair Group 19 – Cooling System outlines checks for the coolant expansion tank cap and never references a serviceable cap on the radiator, and Audi’s genuine parts catalogue (ETKA) diagrams for the Q5 radiator assembly show no cap on the radiator, with a separate expansion tank and its pressure cap listed as the service item.

Why no radiator cap? Audi’s cooling layout is designed around continuous de‑aeration and stable pressure control via the expansion tank. That brings a few benefits:

• Packaging and reliability: a plastic/composite radiator with quick-connect hoses stays sealed, with fewer service openings that can leak.
• Consistent pressure and temperature: the reservoir cap’s relief valve maintains the system at roughly 1.2–1.5 bar, raising the coolant boiling point and helping thermal stability.
• Safe, simple servicing: topping up and bleeding are done at the highest point (the tank), so there’s no need to open a hot radiator neck.

Shopping for a “radiator-cap” for a 2016 Audi Q5 will usually point to the wrong part. The correct service item is the coolant expansion tank cap. If there are signs of coolant loss, hard upper hoses shortly after start-up, or staining around the reservoir neck, the cap’s seal or relief valve may be tired. Replace the reservoir cap with a quality, correct-spec item, inspect the tank for cracks, and only open the cap when the engine is completely cool. Use the correct Audi/VW-approved coolant (G13/G12++ family) mixed to spec, and bleed the system per the workshop procedure to avoid air pockets.

If a parts listing specifically says “radiator-cap” for a 2016 Q5, it’s likely just naming convention. On this model, the functional equivalent is the expansion tank pressure cap.

Popular questions about the 2016 Audi Q5 radiator-cap

Where is the radiator cap on a 2016 Audi Q5?
There isn’t a cap on the radiator itself. The pressure cap is on the coolant expansion tank under the bonnet. That’s the only place you should open to top up or bleed the system, and only when the engine is cold.

Can a universal radiator cap be used on a 2016 Q5?
No. Use a cap designed for the Audi/VW expansion tank with the correct pressure rating and fitment. A generic “radiator neck” cap won’t fit and can cause sealing or pressure issues.

When should the expansion tank cap be replaced?
If there are coolant smells, dried pink residue around the tank, frequent low-coolant warnings, or hoses that go rock-hard quickly after a cold start, test or replace the cap. Many techs treat the cap as preventive maintenance around major cooling service intervals or after any overheating incident.