1999 CHRYSLER 300M

Typical onset: 80,000-150,000 mi

Symptoms: Low oil pressure warning at idle when warm, Rod knock or main bearing rattle on cold starts, Heavy oil consumption (1 qt per 500-1000 miles), Check engine light with camshaft position sensor codes, Metal shavings in oil filter during changes

Fix: The 3.5L V6 sludges badly if oil changes were extended beyond 3,000 miles or lower-grade oil used. Once bearings are damaged, you're looking at either a complete engine rebuild (18-24 hours labor) or short block replacement (16-20 hours). Includes machine work, new bearings, piston rings, timing components, and gaskets. Many shops recommend finding a low-mileage junkyard engine instead due to cost.

Estimated cost: $3,500-6,500

Typical onset: 90,000-140,000 mi

Symptoms: No overdrive (4th gear), transmission stays in 3rd on highway, Harsh or delayed 2-3 shift, especially when cold, Intermittent limp mode with gear ratio error codes, Transmission slipping between gears under moderate throttle, Metal debris in pan during fluid service

Fix: The 42LE is fragile and solenoid pack failures lead to cascading clutch damage. Early intervention with solenoid pack replacement (4-6 hours labor) can save it if no clutch damage yet. Once slipping occurs, you need a full rebuild or replacement (12-16 hours labor). The transmission oil cooler integrated into the radiator also fails, causing cross-contamination—always replace radiator during transmission work on these.

Estimated cost: $2,800-4,200

Typical onset: 100,000-150,000 mi

Symptoms: Pink milkshake appearance in coolant overflow tank, Coolant level drops with no visible leaks, Transmission fluid appears lighter/diluted or foamy, Transmission overheating or erratic shifting, Sudden transmission failure after radiator leak

Fix: The internal transmission cooler in the radiator fails, allowing coolant and ATF to mix. This is a death sentence for the 42LE transmission. Requires immediate radiator replacement (2-3 hours) PLUS full transmission flush and filter, or rebuild if damage already occurred. Preventive radiator replacement at 100k is cheap insurance. Install external auxiliary cooler when replacing radiator.

Estimated cost: $400-800 (preventive); $3,200-4,800 (with transmission damage)

Typical onset: 70,000-120,000 mi

Symptoms: Coolant weeping from front of engine below timing cover, Coolant smell in cabin or under hood when parked, Slow coolant loss requiring top-ups every few weeks, Temperature gauge creeping higher than normal center position, Visible green coolant residue on water pump pulley

Fix: Water pump bearing seals fail and the plastic thermostat housing cracks at mounting ears. Water pump requires timing belt area access (4-6 hours labor) so always replace timing belt, tensioner, and thermostat housing simultaneously even if belt looks good. This is your 90k-mile service whether Chrysler called for it or not.

Estimated cost: $800-1,200

Typical onset: 80,000-130,000 mi

Symptoms: Heavy clunk when shifting from reverse to drive or vice versa, Excessive engine movement visible when revving in park, Vibration through steering wheel at idle with AC on, Thud felt through chassis on acceleration from stop, Difficulty shifting into gear when engine running

Fix: Hydraulic engine mounts fail internally and transmission mount tears. Front mount is worst (2 hours labor), upper torque mount also common (1.5 hours). Access requires supporting engine from above. Replace all three engine/trans mounts as a set if one fails—labor overlap saves money and others are same age.

Estimated cost: $450-750

Typical onset: 90,000-140,000 mi

Symptoms: Battery warning light flickering or staying on at idle, Voltage gauge reading below 13V or fluctuating wildly, Dead battery after overnight park despite new battery, Dimming headlights at idle, brightening with RPM, Electrical accessories acting erratically (radio resets, clock loss)

Fix: Alternator voltage regulator fails internally, causing undercharge or overcharge. The alternator is buried low on the passenger side (2.5-3 hours labor) requiring wheel and splash shield removal. Use OEM or premium rebuilds only—cheap parts store alternators fail within 6 months on these. Check battery cables for corrosion during replacement.

Estimated cost: $400-650

Symptoms: No-start condition, cranks but won't fire (often when hot), Stalling at idle after highway driving, restarts after cooling, Intermittent check engine light with P0320 code, Loss of tachometer signal during operation, Car cranks endlessly without starting, then fires randomly

Fix: Heat-related crank sensor failure strand you unpredictably. Sensor is behind timing cover near crank pulley (1.5-2 hours labor) requiring accessory belt removal. Many techs replace cam sensor simultaneously for peace of mind since labor overlaps. This is a known weakness—carry a spare sensor if you're keeping the car long-term.

Estimated cost: $250-400