Genuine Honda thermostat with housing 19301-PNA-003 – K20 Civic / CR-V / FR-V / Stream

Genuine Honda thermostat with plastic housing 19301-PNA-003 – K20 engines

Genuine Honda thermostat assembly, part number 19301-PNA-003, designed for selected K20 petrol engines. This unit is supplied as a complete thermostat integrated into a moulded plastic housing with outlet neck, controlling coolant flow between the engine block and the radiator to keep the engine at the correct operating temperature.

The assembly is mounted on the engine side of the cooling system and opens at a factory-set temperature. This ensures fast warm-up after cold start and stable coolant temperature during normal driving, protecting the engine from both overheating and running too cold.

Applications

• Honda Civic 3D Type-R 2001–2005 – engine K20A2
• Honda Civic 5D 2004–2005 – engine K20A3
• Honda CR-V 2002–2006 – engine K20A4
• Honda FR-V 2005–2006 – engine K20A9
• Honda Stream 2001–2005 – engine K20A1

Note: always confirm compatibility by VIN in the Honda parts catalogue, especially for facelift / crossover years and imported vehicles.

OEM reference numbers

• 19301-PNA-003 – thermostat with plastic housing and outlet, Honda K20 engines (selected models)

Use the OEM number together with the VIN to make sure you are ordering the correct thermostat assembly for your car.

When to replace – typical symptoms

• engine takes a very long time to warm up or coolant temperature gauge stays unusually low,
• temperature fluctuations while cruising at constant speed,
• overheating in traffic or under load despite a working radiator fan,
• weak or no cabin heating although the engine seems hot,
• warning light or dash message related to coolant temperature,
• visible deposits, ageing or leaks around the plastic thermostat housing and outlet.

A thermostat stuck closed can lead to rapid overheating and serious engine damage, while a thermostat stuck open causes the engine to run too cold, increasing fuel consumption and long-term wear.

Installation and service tips

• this is a complete thermostat assembly with integrated plastic housing and outlet neck – replace the whole unit rather than the insert only,
• drain the coolant to below the thermostat level before removing the old assembly,
• clean the mating surfaces on the engine thoroughly before fitting the new part,
• always use a new seal / O-ring as specified by Honda,
• tighten the housing bolts evenly and to the torque specified in the workshop manual to avoid deforming or cracking the plastic,
• refill the system with the correct Honda coolant (or approved equivalent) and bleed it carefully to remove air pockets,
• after the first test drive, recheck for leaks around the plastic housing and neck and verify that the coolant temperature is stable in all driving conditions.

For long-term reliability, combine thermostat replacement with regular coolant changes according to the service schedule.

FAQ – frequently asked questions about Honda thermostat 19301-PNA-003

Is this an original Honda part?
Yes. This is a genuine Honda OEM thermostat assembly, identical to the part fitted at the factory.

Does this thermostat come with the housing and outlet?
Yes. Part number 19301-PNA-003 is supplied as a complete unit with the thermostat integrated into the plastic housing and outlet neck. You replace the entire assembly.

Will it fit any K20 engine?
No. It fits only the K20 engines listed in the applications section. Always check the part number against your VIN before ordering.

Do I have to bleed the cooling system after replacement?
Yes. Proper bleeding is essential to remove air from the cooling system and to prevent hot spots or overheating after installing the new thermostat.

Is it safe to keep driving with a faulty thermostat?
It is not recommended. A malfunctioning thermostat can cause overheating or chronic under-temperature operation, both of which can lead to costly engine damage over time.