Chevrolet Colorado · Pickup
3.7L inline-5, replacement for the 3.5L with revised cylinder heads. 242 hp, well-suited torque for a small truck. Valve seat issues improved but not eliminated. Water pump and thermostat failures common around 100k mi. A solid truck engine that runs 200k+ miles with regular maintenance.
3.7 I5 — the better five-cylinder
242 hp, revised cylinder heads fix most of the 3.5's valve seat drama. The I5 torque curve suits a small truck. Same 4L60-E concerns, same frame rust lottery. A solid work truck motor that runs 200k+ miles with regular oil changes.
Engine Weaknesses 2
The 3.7L I5 improved upon the 3.5L valve seat issues but did not fully resolve them. GM issued an internal bulletin for specific VINs.
Symptoms: Misfire codes, rough idle, Check Engine Light
Water pumps and thermostats are common wear items on the I5 engines. Failure typically around 100k mi. Fan clutch can also seize.
Symptoms: Coolant leak from water pump, overheating at idle, temp gauge rising
Vehicle Weaknesses 5
Box frame design traps water and road salt, causing severe frame corrosion. Driver-side rear near leaf spring is the first failure point. Aftermarket frame repair kits (Rust Buster) available but costly.
The 4L60-E suffers from weak sun shells and 3-4 clutch packs. Loss of reverse/2nd/4th indicates sun gear failure. Rebuild with hardened sun shell extends life.
Wire harness chafes at door hinge area, blowing fuse #42 and disabling windows and locks. GM TSB PIT3164B covers 2004-2009.
The resistor controlling HVAC fan speed fails prematurely. Fan only works on highest speed. Check blower motor for excessive current draw.
Fuel gauge sensor fails, reading higher than actual level. Requires dropping fuel tank for replacement.
