Here's a breakdown of the likely culprits and how to investigate:
1. Overheating Damage: Overheating can cause catastrophic engine damage. The most common issues stemming from overheating are:
* Head Gasket Failure: This is the most likely culprit. Overheating often warps the cylinder head, cracks the block, or blows the head gasket. This allows coolant to mix with oil (creating a milky substance in the oil) or to leak into the cylinders, causing compression loss, misfires, and a no-start condition. Check your oil for milky residue. A compression test is essential here to check for compression in each cylinder. Low or uneven compression strongly indicates a head gasket problem.
* Warped Cylinder Head or Cracked Block: Similar to a head gasket failure, a warped head or cracked block prevents proper sealing and compression. This requires professional diagnosis and likely machine work (or a new engine).
* Internal Engine Damage: Overheating can also damage pistons, connecting rods, or other internal components. This would require a more extensive internal inspection.
2. Diagnostic Trouble Codes (DTCs): You mentioned codes 55, 65, 11, and 12. These are Jeep-specific codes. While you've replaced the crank sensor, you should still verify the codes. A proper OBD-II scanner is needed here, not just a check engine light reader.
* Code 55: Usually indicates the end of the diagnostic trouble codes. This is common to see.
* Code 65: Could relate to the speed sensor.
* Code 11: Typically means the system is functioning correctly (no errors).
* Code 12: Usually represents that the system has completed a power-up diagnostic.
3. Other Possibilities (Less Likely After Overheating):
* Fuel Pump Relay or Fuel Pump: Although you say you have gas, double-check that the fuel pump is functioning correctly and providing adequate pressure.
* Ignition Coil or Ignition Module: While you mentioned spark, a weak spark might not be enough to ignite the fuel properly, especially if there's compression loss due to overheating.
* Camshaft Position Sensor (CMP Sensor): Similar to the crank sensor, this can cause no-start conditions.
What to Do Next:
1. Coolant Check: Check your coolant level. If it's low and you see milky oil, you likely have a blown head gasket.
2. Oil Check: Inspect your oil for milky residue (like mayonnaise). This is a strong indicator of a head gasket problem.
3. Compression Test: This is vital. A compression test will tell you if you have compression in each cylinder, indicating whether pistons and rings are damaged and whether head gasket is functional. Low compression after overheating is a bad sign.
4. Professional Diagnosis: Based on the overheating and the symptoms, it's strongly recommended to have a qualified mechanic diagnose your engine. They can perform a proper compression test, leak-down test, and possibly a cylinder-leak test to determine the extent of the damage.
Important: Driving the vehicle with a blown head gasket or other significant engine damage can cause further, irreversible damage. Do not attempt to start the vehicle repeatedly if there are indications of internal damage. Towing it to a mechanic is your best course of action.
