Here's a breakdown of the likely culprits and how to investigate:
1. Head Gasket Failure: This is the most likely culprit given your symptoms. A blown head gasket allows coolant to leak into the cylinders, causing the white smoke (steam). The coolant disrupts the combustion process, leading to rough running, misfires, and stalling.
* How to check: Look for signs of coolant leakage:
* Around the cylinder head: Inspect the head gasket area for signs of coolant stains, weeping, or bubbling.
* In the oil: Check your engine oil. If it's milky or has a chocolate milkshake appearance, it means coolant is mixing with the oil – a definite sign of a head gasket problem.
* Coolant loss: Monitor your coolant level regularly. Consistent loss points towards a leak somewhere, likely the head gasket.
* Compression test: A compression test will show if one or more cylinders are losing compression due to a blown head gasket. A leak-down test is even more precise.
2. Cracked Cylinder Head or Block: A crack in the cylinder head or engine block can also allow coolant to enter the combustion chamber, producing similar symptoms. This is less likely than a blown head gasket but needs to be considered.
* How to check: Pressure testing the cooling system can sometimes reveal a crack. A visual inspection of the head and block is also necessary, though often difficult without removal.
3. Coolant Leak into Intake Manifold: A less common issue but possible. A crack or a failing gasket in the intake manifold could allow coolant to enter the intake system.
* How to check: Inspect the intake manifold gaskets for damage or leakage.
4. Other less likely possibilities:
* Clogged Catalytic Converter (if equipped): While less likely to cause the white smoke, a severely clogged converter can restrict exhaust flow, causing rough running and stalling.
* Ignition System Problems: While unlikely to cause white smoke, ignition issues can contribute to rough running and stalling. Check your spark plugs, wires, distributor cap, and rotor.
What to do next:
1. Safety First: Do not continue driving the car with these symptoms. Driving with a blown head gasket can cause catastrophic engine damage.
2. Coolant Level Check: Immediately check your coolant level. If it's low, this reinforces the coolant leak suspicion.
3. Oil Check: Check your engine oil for the milky/chocolate milkshake appearance.
4. Professional Diagnosis: Given the severity of the symptoms and potential for significant damage, it's best to take your Mustang to a qualified mechanic specializing in classic cars. They have the experience and tools (like compression and leak-down testers) to properly diagnose the problem. A head gasket replacement is a major repair job.
Don't attempt major repairs yourself unless you have significant engine repair experience. A misdiagnosis or improper repair can worsen the problem and lead to much higher repair costs.
