Reliability
Cooling system overhaul
Protects the engine
Hard$300–$1,0004–6 hrs
⚠ If the temperature gauge ever climbs past the middle, pull over and shut the engine off right away. Never open the cooling system while it's hot.
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BMW 3 Series E46 mods
Fix the cooling system first. The E46's plastic cooling parts are its best-known weak spot, so a fresh cooling system protects the engine before you add anything else.
Your E46
Pick your year so we only show parts that fit your car.
In the US, 1999 E46s were sedans only, and 2006 E46s were coupes and convertibles only. M3s aren't covered yet.
Engine 2.5–3.0L inline-6
Stock ~170–225 hp
Weight ~3,100–3,400 lb
1999–2006
Reliability
Rear subframe reinforcement
Prevents floor cracks
Expert$150–$2,500Shop job (1–2 days)
⚠ This needs structural welding near the fuel tank and lines, and bad welds can weaken the car in a crash. Have an experienced BMW or fabrication shop do it. If you hear clunking from the rear when you get on or off the gas, have the car inspected before driving it hard.
Reliability
Spark plugs + ignition coils
Fixes misfires
Easy$60–$3501 hr
Power
Cold air intake
+5–10whp est.
Easy$300–$4001 hr
Sound
Cat-back exhaust
+3–8whp est.
Medium$1,000–$1,5002–3 hrs
Handling
Coilovers
Handling + stance
Hard$1,100–$1,4005–7 hrs
⚠ Coilovers change the alignment a lot. Get a professional alignment right after installing them.
Handling
Sway bars
Less body roll
Medium$650–$8502–3 hrs
Brakes
Brake pads + fluid
Firmer pedal
Medium$180–$3002–3 hrs
Horsepower numbers are estimates at the wheels (whp) based on typical results. Real gains vary. Some exhaust and emissions mods aren't street-legal everywhere, so check your local rules.