Mishimoto MMHOSE-WRX-01BL Silicone Radiator Hose Kit for 2001–2007 Subaru WRX and STI

Reinforced Silicone Construction

The hoses combine high-grade silicone with heat-resistant embedded fibers. This reinforced construction provides better tolerance for engine heat and cooling-system pressure than worn factory rubber hoses.

Key features include:

• Reinforced high-grade silicone
• Heat-resistant embedded fibers
• Maximum temperature rating of 330°F
• 1.50-inch inside diameter
• 1.85-inch outside diameter
• Preformed factory-style bends
• Blue finish
• Mishimoto Lifetime Warranty

The blue color provides a period-correct aftermarket look for a GD Subaru engine bay. The early 2000s are apparently vintage now, which feels unnecessarily personal.

What’s Included?

The kit contains:

• One blue silicone upper radiator hose
• One blue silicone lower radiator hose
• Four worm-gear hose clamps

It replaces the two main radiator hoses. It does not include every heater, bypass, turbocharger or expansion-tank hose in the cooling system.

Factory-Style Hose Routing

The upper and lower hoses are molded to connect the turbocharged EJ engine to a factory-location radiator. They can also work with many direct-fit aluminum radiators retaining the original inlet and outlet positions.

Verify fitment carefully if the Subaru has:

• A rotated turbocharger setup
• A front-mounted intercooler with modified piping
• An aftermarket coolant expansion tank
• A nonstandard radiator
• An engine conversion
• Modified water-pump or thermostat connections
• A thicker radiator with reduced hose clearance

When Should WRX or STI Radiator Hoses Be Replaced?

Inspect or replace the hoses when you find:

• Cracks near either connection
• Soft or swollen sections
• Coolant residue around the clamps
• Oil contamination
• Abrasion against a fan or bracket
• A hose that collapses after shutdown
• Recurring coolant loss
• Coolant odor after driving
• Temperature fluctuations or overheating

Follow our coolant-leak diagnostic guide if the source is unclear. Check the radiator end tanks, water pump, thermostat housing and coolant expansion tank instead of assuming the most colorful component is guilty.

Installation Overview

Never remove a radiator or expansion-tank cap while the engine is hot.

A typical installation involves:

1. Allow the engine to cool completely.
2. Photograph the original hose routing.
3. Drain enough coolant to empty both primary hoses.
4. Remove the factory clamps.
5. Carefully separate the hoses from their connections.
6. Inspect the radiator necks and engine fittings.
7. Clean every sealing surface.
8. Compare the new hoses with the original parts.
9. Install each hose without twisting or stretching it.
10. Position each clamp behind the fitting bead.
11. Verify fan, belt and accessory clearance.
12. Refill with Subaru-compatible coolant.
13. Bleed the cooling system carefully.
14. Confirm radiator-fan operation.
15. Inspect every connection at operating temperature.
16. Recheck the coolant level after the engine cools.

Use our cooling-system flush guide if the old coolant is contaminated, rusty or mixed with an unknown formula.

Bleeding a Turbo Subaru Cooling System

Air trapped in a WRX or STI cooling system can cause unstable temperatures, poor heater output and localized overheating. Fill the system slowly and follow the correct Subaru bleeding procedure for the specific model.

Stop the engine if:

• The temperature gauge rises abnormally
• The heater suddenly blows cold
• Coolant erupts from the expansion tank
• The upper hose remains cold as the engine overheats
• Steam appears
• Cooling fans fail to operate

Our guide to a car overheating while the heater blows cold explains why low coolant or an air pocket can produce that combination.

Inspect the Complete Cooling System

New hoses cannot repair a failed thermostat, water pump, radiator or head gasket. While the coolant is drained, inspect:

• Radiator core and end tanks
• Pressure cap
• Coolant expansion tank
• Water pump
• Thermostat
• Cooling fans and relays
• Heater hoses
• Turbocharger coolant lines
• Timing-belt service history
• Coolant condition

Our complete car cooling-system guide explains how these components work together.

For an overheating WRX or STI, also consult:

• Why a car overheats while driving
• Seven signs of a failing radiator
• Bad thermostat versus bad water pump
• How to deal with overheating
• Can radiator stop-leak cause damage?
• When should you stop driving?

Frequently Asked Questions

What U.S. model years does MMHOSE-WRX-01BL fit?

It fits the 2002–2007 U.S.-market Subaru Impreza WRX and the 2004–2007 U.S.-market Impreza WRX STI.

Why does Mishimoto list 2001–2007?

The 2001 model year applies to international-market WRX and STI models. U.S. sales began later.

Does it fit both the 2.0L and 2.5L WRX?

Yes. It fits applicable EJ205-powered 2002–2005 WRX models and EJ255-powered 2006–2007 WRX models.

Does it fit the EJ257 STI?

Yes. It fits applicable 2004–2007 U.S.-market STI models with the EJ257.

Does it fit a naturally aspirated Impreza 2.5i?

It is not officially marketed for the naturally aspirated 2.5i. Purchase according to the exact engine and factory hose layout.

Does it fit a Saab 9-2X Aero?

Some catalogs associate related Subaru cooling components with the turbocharged 9-2X Aero, but verify directly with Mishimoto before ordering. The published application is the Subaru WRX and STI.

Are the upper and lower hoses included?

Yes. The kit contains both main radiator hoses and four clamps.

Will it work with an aluminum radiator?

It should fit a direct-replacement radiator with factory-position connections. Verify custom or oversized radiator layouts.

Will silicone hoses prevent head-gasket failure?

No. They can prevent hose-related coolant loss, but they cannot correct overheating caused by combustion leakage, poor coolant circulation or another mechanical fault.

Product Specifications