Subaru Aisin Water Pump & Japan OEM Timing Belt Kit 2004-2014 STI - TKF-004

The Aisin TKF-004 Subaru timing belt kit for a 2004-2014 Subaru STi features an OEM Aisin water pump & complete OEM timing belt kit with all Japan components. All bearings are 100% authentic - made in Japan; this kit was put together to offer the best water pump & timing belt components for your Subaru EJ257. This timing belt kit pairs an Aisin water pump with a Mitsuboshi belt and Japanese‑brand idlers/tensioner for a durable complete timing belt kit that enthusiasts trust for an EJ257.

This complete timing belt kit is the go to for when you are due for timing service or have the front of the engine open for other work. It eliminates part‑mix guesswork and reduces repeat labor by replacing the pump, belt, idlers, and hydraulic tensioner together with components from OE suppliers. Timing belt & components are suggested by Subaru to be replaced every 105,000 miles or every 7 years. If you are doing a full rebuild and you are close to one of those numbers, we highly suggest this service is performed.

Aisin TKF-004 - Features

• Complete timing belt kit: water pump, timing belt, hydraulic tensioner, and idler pulleys
• OEM top tier components: Aisin water pump, Mitsuboshi timing belt, NTN hydraulic tensioner, and NSK/Koyo idler bearings for factory‑level reliability.
• Carbon‑ceramic mechanical seal in the coolant pump helps prevent coolant leaks under EJ‑series heat cycling.
• Die‑cast aluminum pump body for strength with optimal coolant flow characteristics on EJ257 applications.
• Correct fit for STi EJ257 timing layout; avoids mismatched idlers/tensioner issues seen with mixed‑brand kits.
• Includes installation gaskets and instructions to streamline the service.

Aisin TKF-004 - Fitment

• 2004-2014 Subaru WRX STi
• 2002-2007 Subaru WRX
• 2004-2007 Subaru Forester XT
• 2005-2009 Subaru Legacy GT
• 2005-2009 Subaru Outback XT
• 2004-2006 Subaru Baja Turbo
• 2006 Saab 9-2X Aero Turbo

Compatibility Notes

• Forester XT coverage is for models equipped with the OEM oil cooler; vehicles without the OEM oil cooler typically use Aisin TKF-005.

Frequently Asked Questions

What exactly is included in the TKF-004 kit?

The kit is a full timing service bundle: Aisin water pump with required gaskets, a Mitsuboshi timing belt, a hydraulic tensioner assembly, and the correct idler pulleys from established Japanese bearing manufacturers. It’s designed so you do the job once with matched components instead of mixing brands.

Why replace the water pump with the timing belt?

Accessing the timing belt on an EJ engine requires much of the same labor as replacing the water pump. Doing both together avoids duplicating labor later and reduces the risk of a near‑term pump failure that would require reopening the front of the engine.

Is TKF-004 specific to the STi EJ257 layout?

Yes. The TKF-004 is for EJ257 timing component geometry used on the 2004–2014 STi. That means the idler mix and hydraulic tensioner are correct for this layout, helping maintain factory timing stability and belt engagement.

Do I need any other gaskets or small parts?

The essentials for the pump and timing service are in the box. Many technicians also install a fresh OEM thermostat and new accessory belts at the same time for a fully refreshed front‑of‑engine service, but those items are not part of the TKF‑004 kit.

How often should STi owners plan timing service?

Service intervals vary by operating conditions and region, but many owners plan belt and pump service roughly in the 60,000–100,000 mile window or by time if the vehicle is low mileage. Inspect your maintenance records and follow conservative practices if the history is unknown.

Install Notes

• Always verify belt timing marks at each cam and crank sprocket before tensioning and during final rotation checks.
• Pre‑fill and bleed the cooling system per Subaru procedures; confirm heater function and top off after the first heat cycle.
• Use a new thermostat and fresh coolant if service history is unknown; inspect accessory belts while the front covers are off.
• Do not reuse old idlers or tensioner components with a new belt; the kit is engineered to be installed as a matched set.

Package Contents

• AISIN water pump with gaskets OEM PN: 21111AA240 & 21116AA010
• Mitsuboshi timing belt OEM PN: 13028AA240
• NTN hydraulic tensioner assembly OEM PN: 13033AA042
• NSK and Koyo idler bearings (set) OEM PN: 13073AA142
• Timing Cover Z-bend Gasket OEM PN: 21116AA010
• Installation instructions

Warranty

AISIN aftermarket parts are warranted against defects in materials and workmanship for 12 months / 12,000 miles from the date of purchase/installation, to the original purchaser. Labor and incidental damages are excluded; claims are routed through the place of purchase for inspection.