ERC5923 Oil Cooler Thermostat – Defender / Discovery I / Range Rover Classic

This Oil Cooler Thermostat (Part No. ERC5923) regulates engine oil temperature by controlling flow to the oil cooler, helping the engine warm up efficiently while preventing overheating under load. When this thermostat fails, symptoms can include high oil temperature, poor lubrication, or excessive cooling—making this replacement essential for proper oil system performance on classic Land Rover diesel engines.

Manufactured to OEM-style specifications, ERC5923 installs directly into the oil filter housing assembly on 200Tdi and 300Tdi engines.

Verified Fitment (200Tdi & 300Tdi Engines):

• Defender (1983–2006) – 200Tdi / 300Tdi

• Discovery I (1989–1998) – 200Tdi / 300Tdi

• Range Rover Classic (through ~1994) – 200Tdi / 300Tdi

 This part does NOT fit Td5, Tdci (Puma), or petrol V8 models.

Supersession Part Numbers

No supersessions found.

FAQ

What does the oil cooler thermostat do?
It opens and closes based on oil temperature to regulate whether oil circulates through the cooler.

Does this fit both 200Tdi and 300Tdi?
Yes — ERC5923 is confirmed for both engines' oil cooler assemblies.

What are signs of failure?
High oil temps, slow warmup, or oil cooler bypass not functioning properly.

Part Number: ERC5923

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