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1998 Volvo 70 Series Noise Under the Hood

Hey, everybody. Crescendo-ing fan type noise in caller’s 1998 Volvo V70 is probably the air pump. I think the noise is more akin to a vacuum cleaner. Noise can go on for some time without setting a code. When air pump code does get set, repair involves replacing the pump and its control valve. The control valve’s diaphragm leaks water vapor from the exhaust system into the pump and ruins it.

Gentlemen: As to Joyce, with the 1998 Volvo S70, with thwe mystery noise, it’s the Secondary Air Pump. Trust me. it’s probably working normally, but the reason she’s now hearing it is its just beginning to fail, and getting louder. As you advised her, the Check Engine Light will likely be on soon for this problem. I’ll even advise you on the prospective DTC’S: Some combination of P0442, 446, and 448, will be stored. The PAIR valve is bad to malfunction on these cars, and when it does, it slowly fills the pump with condensation water from the exhaust. Very common problem on these cars. 1998 was the last year Volvo utilized the secondary air system in their cars. With 1999, the cars came equipped with Variable Valve Timing for the first time, thereby improving emission performance and eliminating the need for the secondary air system. I worked as a Volvo technician in the local dealership here for almost 22 years, and since September of 2009, I have been employed in a top shelf independent shop here in town. I still specialize in Volvos. My name is Tim, and I am in Hickory, North Carolina. Been a Mechanic all my adult life, I suppose I have been professionally employed as one for around 25 or 26 years now. I am an avid Car Talk listener as well. I work every other Saturday, from 9 to 1, and while working I always catch the show here at 10 am on WFAE. Thank you,
Tim. PS… Try and contact Joyce, and let her know what’s up with her car, thanks.

Joyce had such a lovely voice and sense of humor that I had to register on the site and leave a comment, however completely off topic. I was smitten. And now I await the flag:)-Laura

There you go Laura. I don’t want to disappoint a lady.

When dealing with a 14 year old Volvo all I have to say is that hearing anything under the hood would be a comforting feeling. It’s probably the air pump but it’s hard to diagnose the problem without hearing the engine.

Air pump sounds likely and should be checked as commented above.

I’ve heard a similar sound coming from a non-Volvo engine that had a vacuum leak. The vacuum leak affected the fuel metering system, discombobulating the idle, and caused the engine idle speed to speed up and slow down more or less at random. When it did this, it was sometimes difficult to get it into gear as the idle speed was too high. If the caller is noticing difficulty engaging the gears, or clucking sounds when engaging gears, a vacuum leak should also be considered.