Replacing the Radiator on the Honda Accord or Acura CL (F23)
If your radiator is leaking, you should replace it rather than try to repair it. Do not try to plug a leaky radiator by adding a "stop-leak" fluid to the cooling system.
You can remove the old radiator and install a new replacement in approximately 1.5 hours with no special tools. In addition, the removal/installation process outlined within these instructions can be performed above the car: that is, in most cases, you won't have to lift up the car and get under it to remove the splash pan and lower radiator hose.
If the radiator failure was due to contaminated, worn-out coolant, you will want to drain any residual coolant from the engine block and consider replacing the thermostat. The upper and lower radiator hoses, however, do not need to be replaced along with the radiator on the Accord, in most cases.
The Risks of Using Aftermarket Coolant and Tap Water
None of the Honda radiators I know about that failed and had to be replaced were using the genuine Honda blue coolant. Their coolant had been switched before the failure to some other non-OEM (non-Original Equipment Manufacturer) green coolant. On some, their coolant reservoir still contained the original blue coolant, showing that the system was never flushed out, but the fluid in the cooling system itself was green with signs of residual blue.
If you switch from "factory blue" coolant to a green coolant, flush the system with water thoroughly before switching. Better yet, stick with the Honda blue coolant.
I believe mixing different colored coolants causes a reaction that reduces the anti-corrosion and pump-lubricating properties of the factory coolant. Many aftermarket coolants contain inexpensive anti-corrosion additives (borates and silicates) not present in Honda coolant. Most Asian coolants use phosphates as an aluminum corrosion inhibitor.
Also, don't dilute your coolant with tap water. Use only distilled, de-ionized, or de-mineralized water. Adding mineral-rich tap water to aftermarket coolant to dilute it to a 50/50 mix will aid in the destruction of aluminum components and rubber seals within the cooling system.
Choosing a Radiator
The radiator on the Honda Accord is composed of aluminum and plastic. Its design and form is very close to Toyota's, probably because KOYORAD is the main supplier for both makes. If you want the absolute best radiator for your Honda, get a Koyo. Aftermarket radiators (non-OEM, that is, not from the Original Equipment Manufacturer) can be purchased anywhere from $100.
When purchasing a radiator replacement, ensure the replacement has all ports that match the original radiator with new brass fittings for the transmission supply and return lines. The bracket mounts for the two fan shrouds should match as well. Some replacement radiators do not come with a drain port and plug but the better ones do.
Radiator Component Details
Removing the Old Radiator
1. Remove the radiator filler cap and detach the radiator reservoir hose.
2. Detach the electrical connectors to the two fan shrouds.
3. Remove the drivers-side fan shroud assembly by unbolting the two 10mm bolts to the upper left and right corner of the shroud.
4. After the two bolts have been removed, you can pull the shroud straight up and off the radiator. This will expose the lower radiator hose clamp and the radiator drain plug to ease access.
5. After the shroud has been removed, reach down and twist the drain plug counter-clockwise until coolant begins to flow from the drain port.
6. After the coolant has been drained, remove the lower radiator hose clamp and detach the hose from the radiator.
6A. Alternative Hose Detachment: If you want to replace the lower hose along with the radiator, detach the lower hose from the thermostat housing. Then you can pull out the radiator with the lower hose attached. However, to access the thermostat housing you will have to remove the air intake hose.
7. Detach the transmission fluid supply and return lines.
8. Unbolt the two left and right radiator brackets.
9. Pull the radiator out with the drivers-side fan shroud attached. Unbolt the shroud after removal.
Installing the New Radiator
1. Attach the new brass ATF fitting onto the new radiator and transfer the ATF lines from the old radiator to the new radiator.
2. Transfer the driver- and passenger-side fan shrouds to the new radiator. If you do not feel comfortable fitting the lower radiator hose to the new radiator with the passenger side shroud attached, you can attach it after the lower hose has been secured with the hose clamp.
3. Fit the new radiator so that its two bottom plastic prongs go into the rubber radiator mounts. Sometimes these mounts come off in the process of removing the old radiator. Therefore ensure that these rubber mounts are in their radiator mounting holes before mounting the new radiator.
4. Connect the upper radiator hose, the two radiator brackets, the coolant overflow hose, the two fan shroud electrical fittings, and the ATF supply and return lines.