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Unveiling the Mystery Behind Volvo 3.2 Engine Noise: A Tale of Diagnosis and Repair

We have done a few of these recently and thought that we would share the story of the worst one.

One of our great customers recently purchased a well looked after 2011 Volvo XC70. This particular Volvo is equipped with the 3.2 engine. He noticed that under slight acceleration, there was a growling/humming noise and it was gradually getting worse. It should also be noted that the noise only occurred when the engine was in gear - not in park or neutral. The customer spent quite a bit of time at home crawling over and under the car trying to pin-point where the noise was coming from, but he eventually had the car towed to us.

We were able to determine that the humming was coming from the READ unit.

Unlike Volvo's long history of 5 cylinder engines, The Volvo 3.2 is a 6 cylinder engine and uses an unconventional accessory layout: While most engines (Volvo and otherwise) use the front of the engine to route a system of belts and pulleys to run the car's features, the air conditioning, power steering and water pump - on the 3.2 all are driven by a serpentine belt on the backside of the engine.

To make this work, Volvo uses the READ. R.E.A.D stands for Rear End Auxiliary Drive. It is a gearbox that is attached to the side of the engine and driven by the crankshaft. It provides an output shaft to drive the alternator and serpentine belt, (which are typically driven off of the front crank pulley).

Unfortunately, this is an expensive repair. It is made potentially MORE expensive by the fact that the READ bearing journals are part of the engine block - if there is damage to the journals made by a spun bearing, the engine block needs replacement. Eeks!

This story has a happy ending.

The READ uses a 1-way clutch pulley to drive the serpentine belt, (it will freewheel if spun in reverse).

We started the engine with the belt removed and...No noise!

We grabbed the pulley and gave it a twist. The clutch was seized! It is a good thing that the customer was using his ears and noticed a problem and had the car towed in.

If the situation continued to get worse, this little pulley could have taken out the timing, the READ and potentially the entire engine! 

We replaced the pulley and put the car back together. It is running smoothly, quietly and reliably again. Hooray!

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