The VW Jetta has a reputation for being a reliable car, but can experience problems during warm weather, such as overheating and difficulty starting. Since overheating problems can be costly, it is better to diagnose and fix the problem on your own than bring it to a mechanic. However, overheating can damage some of the car's components so do not drive the car until you have diagnosed and repaired the problem.
The starter failing is a common problem with the VW Jetta during warmer months. The starter is most likely the problem if the engine is unresponsive when you turn the ignition key, and you hear a clicking sound or no sound at all. If the engine turns over and makes noise, but still does not start, then the starter is not the problem.
A malfunctioning thermostat is the most common cause of a car refusing to start in hot weather. If the thermostat sticks, it will not open properly to allow the coolant to reach the engine. Usually a car will start if the thermostat is not functioning properly, but will stall once the engine is warm and refuse to start again until it has cooled down.
A faulty coolant temperature sensor (CTS) is a common problem with the VW Jetta, which can lead to the car having trouble during hot weather. The CTS sends information to the engine about how hot the engine is running. If your Jetta stalls once it reaches normal running temperatures in hot weather, it could be caused by the CTS miscalculating the engine temperature.
The anti-shudder valve has been known to cause problems for the VW Jetta during hot weather. When you turn your car off, the shudder valve closes to stop air from reaching the engine. If the valve is clogged or dirty, it may stay closed in hot temperatures and prevent your engine from starting.
The mass air flow sensor, or MAF, detects the amount of air flowing into the engine. In warm weather, it can malfunction and send an excessively rich fuel mixture into the engine causing the engine to flood. The weather and engine must cool down before the car starts if the MAF is malfunctioning.
