2006 Volvo s40 clicking noise, loud engine, overheating
 

Hi, all. I've never posted to a forum before so idk really how this works.
My 2006 Volvo s40 (I don't know the engine model...) has been overheating after only 15 mins of driving locally and making loud noises of varying sorts (a whistling and clicking noise, notably). A readout for the check engine light says it needs a Mass Airflow Sensor but I would like a second or third opinion on what to do. I'm a college student and can't afford paying $$$ for just a diagnosis nor do I want to risk going into a repair shop and actually needing to spend more money than expected. Calling local auto repair shops specializing with Volvos, I've gotten quotes for $180-260 for just if it is the mass airflow sensor.

Where are you located? Replacing the MAF sensor is a 15 minute job - and you can buy a replacement part online (try EEUROPARTS.COM or FCPEURO.COM to get a sense of the cost). With that said, that wouldn't explain the overheating and the loud noises. The MAF controls the fuel mix so if its not doing its job, I'd expect symptoms like hard starting, engine stalling, hesitation, jerky power or low power, bad idle. Loud sounds, clicking, overheating may be the sign of a more serious problem like a blown headgasket so you may want a shop to do a proper diagnosis.

The overheating must be addressed ASAP. Overheating will kill an engine. Check the fluid level in the coolant reservoir first.

Regarding the over heating, it the temperature actually indicating high or is it boiling over? If the temp is normal but boiling over at the expansion tank, it may just be the cap on the expansion tank. If you replace it, go with a Volvo cap and not aftermarket. I and others have had problems with even reputable brand aftermarket caps not holding pressure and allowing the coolant to boil. At the normal operating temp, the system must hold proper pressure to raise the boiling point of the coolant.