Radiator Filler Neck - Lexus RX350 & Toyota Sienna 2007-2009 (OE 902408)

A Radiator Filler Neck for the Lexus RX350 and Toyota Sienna

This is a replacement radiator filler neck, OE number 902408, built for the 2007-2009 Lexus RX350 and 2007-2009 Toyota Sienna. If you've noticed coolant seeping from the top of your radiator, a radiator cap that won't seal properly no matter how tight it's turned, or your engine running warmer than usual, a cracked filler neck is a common and often overlooked cause on these two models.

What a Radiator Filler Neck Does

The filler neck is where your radiator cap seats, and it's a more important part than its simple appearance suggests — it has to hold system pressure (typically well over a dozen psi on a hot engine) while providing an airtight seal for the cap and a connection point to the overflow or coolant reservoir hose. On many vehicles, including these two, the filler neck is molded from plastic rather than metal, and plastic exposed to years of heat cycling and UV exposure under the hood gradually becomes brittle, which is why cracking here is a fairly common failure mode as these vehicles age.

Why a Cracked Filler Neck Causes Bigger Problems

Once the filler neck can't hold pressure properly, your cooling system can't maintain the pressure it needs to keep coolant from boiling at normal operating temperatures, which is part of how modern cooling systems avoid overheating even when coolant temperature exceeds what it would boil at under normal atmospheric pressure. Wikipedia's radiator article covers how pressurized cooling systems work and why maintaining a sealed system matters for keeping an engine at a stable operating temperature, if you want the broader technical background beyond this specific part.

Vehicle Coverage

This filler neck is built for the 2007-2009 Lexus RX350 and the 2007-2009 Toyota Sienna specifically. Both vehicles share related powertrain architecture from this era, which is why the same filler neck part fits both, but if you have a Sienna or RX350 from outside the 2007-2009 range, it's worth confirming the OE number matches your vehicle before ordering.

OE and Interchange Numbers

This filler neck is built to OE number 902408, with the interchange numbers 160410P180, 160410P190, and 164100P201 also on file for cross-reference. Matching any of these against your original part is the most reliable way to confirm fitment.

Specifications

• Type: Radiator filler neck (coolant filler neck)
• Material: Plastic, reinforced
• Features: Rust-resistant, protective sleeve attached
• Placement: Upper radiator connection
• Condition: New
• Warranty: 1 year

Installation Notes

Replacing a radiator filler neck usually means draining or lowering the coolant level below the neck, disconnecting the overflow hose and radiator cap sensor wiring if your vehicle has one, unclipping or unbolting the old neck, and seating the new one with a fresh seal before refilling and bleeding the cooling system of air. Getting the system properly bled of air pockets afterward matters as much as the part swap itself, since trapped air can cause localized hot spots even with a perfectly good filler neck installed.

Ordering Information

This filler neck is in stock and ships ready to install. Our Shipping Information page covers current timelines, and our Warranty and Returns pages explain the process if anything isn't right on arrival. If you're not sure this matches your specific model year, our Request a Part page is the fastest way to confirm before ordering.

Related Parts

This filler neck sits in our cooling system collection and our Lexus and Toyota collections. If you're addressing a cooling system issue, it's worth checking your radiator cap and coolant condition at the same time, since a failing filler neck and an old radiator cap often show similar symptoms.