The K&N 57-2529-1 is a cold-air intake kit for the 4.0L SOHC V6 in 2001–2004 Ford Explorers. It is built around a roto-molded, high-density polyethylene tube that the manufacturer says helps increase the volume of airflow to your engine. The kit replaces the factory air filter and intake tube, and a custom heat shield keeps intake air away from engine-bay heat. Against a cheap universal cone, the reusable oiled-cotton filter and the No-Hassle Lifetime Limited warranty are the main reasons to pay more. The manufacturer claims a guaranteed gain in horsepower and torque but does not publish a figure, so judge the upgrade on driveability rather than a dyno number.
Fitment centers on the 2001–2004 Explorer with the 4.0 SOHC engine. The manufacturer's install sheet covers Ford and Mazda applications and states the kit was not designed to fit vehicles with a body lift. Buyers searching for a 4.0 SOHC cold air intake, a FIPK 57 Series setup for a 2001-2004 Explorer, or a 57-2529-1 install guide should confirm their model year and engine against the manufacturer's fitment data before ordering. Owners on user forums point out that exhaust and intake flow through the heads is a major limit on the SOHC's output, so an intake works best as one part of a broader build.
The manufacturer states the kit is street legal and legal for use in all 50 states.
The manufacturer's installation instructions state the kit was not designed to fit vehicles with a body lift. Confirm your vehicle's setup with the manufacturer before ordering.
Per the manufacturer's general K&N guidance, the filter requires cleaning every 100,000 miles under normal highway conditions, and more often in dusty or off-road use. The manufacturer also recommends a visual inspection about every 25,000 miles to check that the screen is still visible.
Yes. The manufacturer lists mounting hardware as included, and the custom heat shield is part of the kit.
Per the manufacturer's install sheet, begin by turning off the ignition and disconnecting the negative battery cable. This erases pre-programmed electronic memories, and some radios will ask for an anti-theft code after reconnection, so write down your settings first. The sequence then covers unplugging the mass air sensor, removing the throttle body cover, detaching the crankcase vent hose, releasing the factory air cleaner, and installing the heat shield and silicone hose on the throttle body. The manufacturer warns that skipping the instructions or the provided hardware can damage the intake tube, throttle body, or engine. Some vehicles have a second vent line, and the sheet covers marking the tube for drilling, so read that section before cutting anything. Owners on user forums report finishing the job in about 1.5 hours with basic hand tools, but published time estimates vary, so confirm the expected time with the manufacturer.
