How to Install a Baffled Coolant Expansion Tank on a 1.5T Civic

Quick Answer

Replacing the factory plastic coolant expansion tank with a PRL baffled aluminum unit is a direct bolt-on upgrade that improves durability and prevents coolant loss under hard driving.

Installation Steps

1. 1. Drain the Coolant: Let the engine cool completely. Place a drain pan under the radiator drain plug and open it. Also remove the factory expansion tank cap to speed draining. Common mistake: draining while hot can warp the new tank or cause burns.
2. 2. Remove the Factory Tank: Disconnect the two coolant hoses from the factory tank using pliers. Unclip the tank from its mounting bracket and lift it out. Save the bracket if reusing. Check the hoses for cracks; replace if brittle.
3. 3. Install the PRL Tank Bracket: The PRL tank uses the same factory mounting points. Bolt the supplied aluminum bracket to the chassis using the original hardware. Torque to 8 ft-lb. Do not overtighten; the bracket is aluminum and can strip.
4. 4. Mount the PRL Tank: Slide the PRL baffled tank onto the bracket and secure it with the provided hardware. Reconnect the two coolant hoses—they only fit one way due to the barbed fittings. Ensure hoses are fully seated and use the supplied spring clamps.
5. 5. Refill and Bleed the System: Close the radiator drain. Fill with the correct Honda Type 2 coolant mixed 50/50. Run the engine with the heater on full until the thermostat opens, then top off the expansion tank to the cold fill line. Air pockets cause false temperature readings; bleed thoroughly.
6. 6. Check for Leaks: Inspect all hose connections and the tank seam for drips after the first heat cycle. Recheck coolant level the next morning. A small drop at a fitting means the clamp needs repositioning.

Product Used in This Guide

• 2017-25 Honda Civic Type R, 2016-21 Honda Civic 1.5L Turbo, 2024+ Acura Integra Type S Baffled Coolant Expansion Tank: Fits 2016-2021 Honda Civic 1.5T, 2017-2025 Civic Type R, and 2024+ Acura Integra Type S. Replaces the factory plastic tank with a baffled aluminum design. Direct fit means no cutting or drilling; the baffles keep coolant from aerating during track or spirited driving.