Gates Honda Civic Radiator Hose Upper Si

Gates Honda Civic Radiator Hose Upper Si

The factory upper radiator hose on a 2002-2005 Civic Si or a 2002-2006 RSX gets soft, cracked, or glazed after two decades of heat. When that hose is done, you need a molded EPDM upper that still leaves room for a cold air intake on a DC5 or EP3 K20. Gates 21229 is that extra-clearance curve. Honda shops have been putting this number on these cars for years.

You get one molded hose. Clamps are not in the box. Gates tells you to replace the clamps when you replace the hose.

What It Is and Why It Works

Gates builds 21229 as a molded EPDM coolant hose with a taller arch than the stock-route upper. Official numbers are a 21.2 in centerline and 1.25 in IDs on both ends. You get more intake room on a DC5 or EP3 K20. You give up the silicone look. It will not dress the bay like a Hybrid Racing silicone pair, and it will not replace the lower hose.

Honda shops have been putting this curve on Civic Si and RSX K20 cars for years. Confirm your radiator neck and thermostat housing before you cut the old hose off. About 1.25 in on both ends and that extra arch is this hose.

Specs

Fitment

One upper hose. Pull the old hose and match both necks: 1.25 in ID, about 21 in of molded length, extra arch for intake room. Shops use 21229 that way on a DC5 or EP3. This does not fit a stock D17 or IMA 7th-gen Civic, an 8th-gen Civic, or a DC2 Integra. A 2001-2005 Civic only makes sense if you are running a K-series swap, not a stock D17. Do not order this for a stock non-Si Civic.

What to Know Before You Buy

Drain the system before you cut anything. Mark the thermostat housing and the radiator neck so the new curve sits the same way. Slide the hose on dry first. If a neck is 1.25 in and the hose fights you, stop and check the part number on the hose in your hand. Gates tells you to replace the clamps with the hose. Reuse a tired worm-drive clamp and you will chase a drip. Fill with the coolant Honda spec'd for that year and burp the system until the heater blows hot.

This is one upper hose. You still need a lower hose if that one is original, a cap that holds pressure, and a thermostat that actually opens. 21229 will not fix a rotten radiator, a weak cap, or a stuck thermostat. If the bay smells sweet after you drive it, look at both ends and the water pump weep before you blame the new hose. A cold-air intake that sat on the old hose will sit better on this curve, but measure the filter and the radiator fan before you assume it clears.

Shops use this as the extra-clearance upper on a DC5 or EP3, and that is why Honda people keep coming back to this number. If you want a matched silicone pair, that is a different product. This is a stock-replacement EPDM hose with a useful shape, not a show hose. And if you are on a stock D17, Hybrid, or GX Civic, this is the wrong hose.