cooling

Radiator Cap

for 2009 Aston Martin DB9 6.0L V12 · RWD

Difficulty

Easy

Time

24 min

Tools

Steps

✓Fact-checked. Built from OLP's spec database, then independently fact-checked line by line with every correction applied. Master-tech sign-off by Chris Hackleman is queued. Cross-check torque values against the factory manual, and stop if anything looks unsafe. How our data is made.

Remove and replace the radiator pressure cap on a 2009 Aston Martin DB9 6.0L V12 to restore proper cooling system pressurization.

Warnings

⚠️Never remove the radiator cap when the engine is hot or warm. Pressurized coolant can erupt violently causing severe burns. Allow the engine to cool completely for at least 2 hours after shutdown.

⚠The DB9 cooling system operates at high pressure. Even when cool, residual pressure may remain. Open the cap slowly to release any remaining pressure before full removal.

ℹ️Coolant may have migrated into the cap area. Keep shop towels ready and work over a drain pan if desired to catch any spillage.

Tools required

Shop towel or ragEssential

Drain pan (optional, for overflow)

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Parts

Radiator pressure cap × 1 — Use OEM specification (typically 16 PSI rating)

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Preparation

Ensure the engine has been completely cool for at least 2 hours since last operation
Open the hood and secure it in the raised position
Locate the radiator cap on top of the radiator assembly at the front of the engine bay
Visually inspect the radiator filler neck for damage, cracks, or corrosion that might affect cap sealing
Place shop towels around the radiator cap area to absorb any coolant spillage

Procedure

1
Verify engine temperature
Confirm the engine is completely cool before proceeding, using the dashboard temperature gauge and by cautiously sensing (without gripping) the upper coolant hose. If any warmth is detected, wait longer. The cooling system retains heat for extended periods on V12 engines due to thermal mass. Note that on the DB9 the pressure cap is located on the coolant expansion/header tank, not necessarily on the radiator core itself. Note: Touch the upper radiator hose and coolant expansion/header tank to confirm the engine is completely cool. Note: Touch the upper radiator hose and the coolant expansion/degas tank to confirm the engine is completely cool.
2
Release residual pressure
Place a shop towel over the radiator cap. Press down firmly on the cap while turning it counterclockwise approximately 1/4 turn to the first detent (safety stop position). Listen for any hissing sound indicating pressure release. Wait until all hissing stops before proceeding.
3
Remove the radiator cap
Once all pressure is released and no hissing is audible, continue pressing down on the cap and rotate it further counterclockwise past the safety stop until it can be lifted straight up and away from the filler neck. Set the old cap aside on a clean surface.
4
Inspect the filler neck seal surface
Examine the radiator filler neck sealing surfaces where the cap gaskets make contact. Look for corrosion, deposits, scratches, or irregularities. If deposits are present, clean the sealing surface with a clean shop towel. Do not allow debris to fall into the radiator.
5
Inspect coolant level and condition
With the cap removed, visually inspect the coolant level in the expansion/header tank. It should sit between the minimum and maximum level markings when cool. Note the coolant color and check for contamination, oil, or debris. If coolant level is low or coolant appears contaminated, further cooling system service may be required. Note: With the cap removed, visually inspect the coolant level. On systems with an expansion tank, the level should sit between the MIN and MAX markings on the tank when cool.
6
Install the new radiator cap
Remove the new radiator cap from its packaging and inspect the rubber gaskets on the underside for damage or defects. Position the new cap over the filler neck opening, ensuring it is aligned with the filler neck tabs. Press down firmly and rotate clockwise until the cap seats fully past the safety stop with a firm, positive click or engagement.
7
Verify cap installation
Confirm the cap is fully seated by attempting to turn it further clockwise (it should not rotate further) and by visual inspection that the cap sits flush and even on the filler neck. The cap should not feel loose or able to lift without pressing and turning.

Reassembly

No disassembly was required; cap installation completes the procedure

Verification

Start the engine and allow it to reach normal operating temperature while monitoring the temperature gauge
Visually inspect the radiator cap area for any coolant seepage or leaks around the cap seal during warm-up
After reaching operating temperature, shut off the engine and allow it to cool for 30 minutes, then carefully check that the cap is still properly seated and shows no signs of leakage
Verify that the cooling system maintains proper pressure by confirming normal engine operating temperature and no overheating occurs during a test drive

🔧Stuck on this radiator cap? Take it to The Diag Desk.A human with 20+ years in the bay answers about YOUR Aston Martin within 24 hours — never AI. $25, and you're not charged unless you get an answer.Ask a tech →