2004 PONTIAC BONNEVILLE

Typical onset: 80,000-120,000 mi

Symptoms: white smoke from exhaust on cold start, coolant loss with no visible leak, overheating, milky oil, coolant in cylinders causing misfire

Fix: Northstar head gasket job requires removing engine or body lift due to tight engine bay. Head bolt threads in aluminum block pull out over time. Proper fix involves time-sert or helicoil installation in all head bolt holes, new gaskets, coolant flush. 18-24 hours labor. Many shops won't touch these.

Estimated cost: $3,500-6,000

Typical onset: 90,000-140,000 mi

Symptoms: transmission fluid leaking near radiator, pink fluid puddles under car, transmission slipping or delayed engagement, overheating transmission

Fix: Steel cooler lines rust through where they connect to radiator or at frame contact points. Requires replacement of affected lines, often both while you're in there. If coolant mixed with ATF, transmission flush or rebuild may be needed. Lines: 2-3 hours. Contaminated trans adds 8-12 hours for rebuild.

Estimated cost: $300-800 for lines only, $2,000-3,500 if transmission contaminated

Typical onset: 100,000-150,000 mi

Symptoms: coolant leak at front of engine, coolant smell in cabin, rough idle when cold, milky residue in coolant reservoir, external coolant puddles

Fix: Plastic intake manifold gaskets deteriorate on Series II 3.8L. Upper and lower intake gaskets should be replaced together. Includes coolant flush, thermostat replacement recommended. 4-6 hours labor. Straightforward job compared to Northstar issues.

Estimated cost: $600-1,200

Typical onset: 80,000-120,000 mi

Symptoms: clunk when shifting into drive or reverse, vibration at idle in gear, excessive engine movement visible from outside, harsh engagement

Fix: Hydraulic transmission mount on passenger side fails, causing drivetrain to shift excessively. Replacement requires supporting engine/trans, unbolting old mount. 1.5-2 hours labor. Easy DIY with proper jack stands.

Estimated cost: $200-400

Typical onset: 90,000-130,000 mi

Symptoms: power steering fluid leak near front of engine, whining noise when turning, hard steering, low fluid warning if equipped, fluid spray on belts causing squealing

Fix: High-pressure hose from pump to rack develops leaks at crimped fittings. Hose runs behind engine requiring removal of accessories for access. 2-3 hours labor. Replace hose, flush system, bleed air.

Estimated cost: $400-700

Typical onset: 120,000-160,000 mi

Symptoms: ABS light on, traction control light on, pump runs constantly, soft brake pedal, poor brake performance, extended stopping distance

Fix: Delphi ABS modulator motor or valve body fails. Unit is integrated, requires complete assembly replacement, brake fluid flush, and bleeding. 2-3 hours labor. Used units available but risky. Rebuilt units more reliable.

Estimated cost: $800-1,500

Symptoms: blower only works on high speed, no blower at lower speeds, intermittent operation, blower stuck on one speed

Fix: Resistor pack behind glove box fails due to heat cycling. Access requires removing lower dash panel on passenger side. 0.5-1 hour labor. Common wear item, straightforward replacement.

Estimated cost: $120-250