* Leak in the AC system: A refrigerant leak is the most likely culprit for the air release sounds and the white smoke (though white smoke *can* also be unburnt fuel, so this needs further investigation). If the leak is significant, the loss of refrigerant pressure can affect the compressor clutch and put extra strain on the engine, leading to hesitation and near-stalling. A failing compressor itself could also produce these symptoms. A proper AC system pressure test is crucial here.
* Coolant leak into the AC system: This is a more serious issue. If coolant is leaking into the AC system, it can mix with the refrigerant, causing significant damage to the AC components and potentially even the engine. The white smoke would be coolant escaping, and the engine hesitation could be due to overheating or air in the cooling system.
* Vacuum leak: While less likely to directly cause white smoke with the AC on, a vacuum leak in the intake system could cause the engine to hesitate and stumble, especially under load (like when the AC compressor engages). This is less likely to be the source of the "air release" sounds unless the leak is extremely large.
* Faulty AC compressor clutch: If the compressor clutch is failing, it might be engaging and disengaging erratically, putting a strain on the engine and causing hesitation. However, this is less likely to explain the white smoke and air release sound unless there's a related leak.
* Blocked or failing radiator: A severely clogged radiator or a failing water pump could cause overheating, leading to engine hesitation and potentially white smoke (though it might be more grey-white, and this wouldn't be directly related to the AC).
What to do next:
1. Return to the mechanic (a different one if necessary): Explain the symptoms clearly and insist on a thorough diagnostic check. The problem requires a mechanic who is experienced with AC systems and engine diagnostics.
2. Specifically request these tests:
* AC system pressure test: This is essential to check for leaks.
* Visual inspection for leaks: Look for coolant leaks around the engine and AC components.
* Coolant pressure test: Check the cooling system for leaks or pressure problems.
* Vacuum test: To check for leaks in the intake manifold.
* Compression test: To check the health of the engine cylinders.
The white smoke and the correlation with the AC are very concerning and warrant immediate attention. Ignoring this could lead to significant engine damage. Don't drive the car extensively until the issue is diagnosed and resolved.
