2001 Chrysler Concorde 69,500 mi - P0300 & P0305 Codes Lead to Engine Failure: Was It Coolant or Bad Coil?
My 2001 Chrysler Concorde (69,500 miles) started showing a check engine light while driving. The car was running normally until I turned a corner, when it hesitated and the warning light activated. After that, no further issues occurred—no stalling or performance problems—until I brought it to a local repair shop on a Saturday for diagnostics three days later. The shop scanned the engine and found fault codes P0300 (random misfire) and P0305 (cylinder 5 misfire). The next morning, they informed me that during testing, the engine 'blew a rod' due to coolant buildup in the oil, claiming the engine was destroyed and requiring a full replacement. They quoted repair costs between $4,500 and $8,000. I then took the vehicle to a dealership for further inspection. They found no visible coolant in the engine oil and concluded that a faulty spark plug coil was likely the root cause—something the first shop should have identified based on the P0300/P0305 codes. I'm now confused: Can a bad coil cause rod failure? And if not, how could coolant be present without being detected? I've added coolant only once—the day I brought the car in—because the temperature gauge was reading higher than normal. Prior to that, no additional fluid additions were needed. The dealership claims they found a defective coil as the cause, but since the engine is not running and has sustained damage, how can a misfire code point to a coil failure without actual engine operation? I'm seeking clarity on whether this was truly an engine failure due to coolant intrusion or simply a misdiagnosis. I need reliable information before deciding between replacing the engine or purchasing a new vehicle.
A bad coil causing rod blowout is highly unlikely. If coolant entered the combustion chamber and was compressed, it could potentially damage pistons or rods—so that part makes sense. But have you ever had to add coolant before this incident? Only on the day of service due to a high temperature reading, correct?