Lexus RX Radiator: Specs, Fitment & Common Faults

A genuinely important finding: this hybrid has a separate inverter coolant system, and if it detects overheating, the car likely won't let you continue driving at all — a protective measure that may mean towing rather than pushing on.

Illustration for editorial purposes

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OEM Part Number: 16400-31A40 (genuine radiator — confirm via VIN, as engine variants exist)

Accuracy note: Covers the Lexus RX (2015-) as listed in the UK aftermarket catalogues. Radiators are sold by engine, gearbox and air-conditioning fitment, and one model usually has two or three different cores — a thicker core for diesels and automatics, a thinner one for small petrols — with different hose positions, so a radiator for the wrong engine will not connect up. The references below are UK aftermarket listings whose fitment lists name this generation, labelled by brand with the core size in mm; genuine numbers are those quoted against the listing. Check your engine code and whether the car has air conditioning against your VIN, and replace the coolant and bleed the system after fitting.

Radiators (aftermarket)	Van Wezel 56012701 (500 x 760 x 27 mm, fits RX 450h GYL20 and 450h AWD GYL25/GYL26); no other-brand cross-references are listed for this radiator.
Core sizes & variants	The hybrid RX 450h uses a wide 760 mm core at 27 mm deep. The RX 200t/300 turbo petrol and the RX 350 have separate radiators under different genuine numbers, and aftermarket cover for them in the UK is thin.
Genuine (OE) numbers quoted	16400-31A40; 16400-31A30; 16400-0P510
Fitment notes	Connection sizes and seal supply are not listed; this unit is a Van Wezel group product and was shown as not available at the time of writing, so a genuine radiator ordered against the VIN is the safer route for this car.

Accuracy note: genuinely worth knowing: coolant capacity and radiator sizing on the RX tend to track engine displacement and power output closely — a part correct for a smaller-engined version of the same model can undersize the cooling for a larger-engined one.

Lexus RX Radiator: The Part That Keeps Everything Else From Cooking

Few parts get less attention than this one, but on the Lexus RX, a neglected cooling system is behind the vast majority of avoidable serious engine failures. Noticing the early warning signs costs nothing and can save a genuinely large repair bill down the line.

Before you buy: radiator size and design vary significantly by engine size, transmission type, and whether your car has air conditioning. Always confirm against your VIN before ordering.

Lexus RX Radiator: What It Does

On the Lexus RX, coolant runs through the radiator to shed engine heat into the airflow, keeping temperatures in check. On many automatics, a separate internal circuit inside the same unit also cools the transmission fluid — one more reason a mismatched part number causes more than just a cooling problem.

Lexus RX Radiator: Watch: Replacing It

🎬 Watch: 2008 - 2016 Toyota Highlander / Lexus RX350 Radiator Replacement (older gen)

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Third-gen RX (AL10); nothing found on the 2015-on AL20

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A Genuinely Important Finding Worth Knowing About This Hybrid's Cooling System — Lexus RX Radiator

This is genuinely important to understand on hybrid variants: there's a genuinely separate inverter coolant system, distinct from the normal engine cooling system, specifically to keep the power electronics at a safe temperature. A leak or low level in this specific system is a different issue from a conventional engine coolant leak, worth knowing so you check the correct reservoir if a hybrid-specific warning appears. It's also genuinely important to know that if the hybrid system detects an overheat, it will likely not allow you to continue driving at all, as a deliberate protective measure specifically to protect the transmission, electric motors, and the high-voltage battery — the car may genuinely need to be towed rather than driven even a short distance, worth accepting this rather than trying to force the car to keep moving.

A genuinely useful, emergency-only tip worth knowing: if the inverter coolant level specifically is found to be low in a genuine emergency, temporarily topping it off with plain water rather than proper coolant can get you safely to your destination, with a proper inspection and refill to follow once there. It's also genuinely worth knowing that diagnosing the exact cause of a hybrid overheat warning is genuinely difficult without a proper scan tool, since retrieving the actual fault codes is necessary to identify which specific component has failed — worth having this done properly rather than guessing at a cause.

It's also genuinely worth knowing a specific finding on certain model years: coolant leaks appearing near the transmission housing junction can be caused by a compromised transmission cooler seal or a cracked housing, rather than the water pump, since the transmission and cooling systems are genuinely integrated on this platform — repair for this specific cause typically requires transmission removal. It's also worth knowing an important DIY warning: always properly dilute coolant concentrate with distilled water according to the bottle's instructions, since undiluted coolant can itself cause overheating, and filling the overflow reservoir with plain water alone risks the reservoir cracking if the temperature falls below freezing.

Lexus RX Radiator: Faults, DIY Difficulty & Aftermarket Advice

These are the same regardless of make or model — see our full Radiator Guide for the three common failure modes, confirming fitment against your VIN, and OEM vs aftermarket guidance.

More Lexus Radiator

The same part, covered across other Lexus models.