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2004 Nissan Pathfinder Armada (Nissan)
2004 Nissan Pathfinder Armada (Nissan)

Rob's Garage

A tricky diagnosis for a squealing SUV Add to ...

I have a squealing noise in the engine compartment of my 2001 Nissan Pathfinder LE. It happens only when I start the engine when it’s cold.

It subsides after a few seconds, but if I turn the steering wheel to start driving, the noise returns for a few more seconds. Then it disappears altogether until the next cold start, to repeat the same routine again.

I checked the drive belts and they look fine. Is this a sign of a sudden breakdown or greater damage?

Thanks, Doug

Doug, I wish I had more positive comments for you, but I’m afraid your Pathfinder noise is part of a much bigger issue.

It turns out that your engine family, the VQ35, is part of a Nissan-wide issue with front-of-engine noise. There are many Internet forums on the subject, but I dug deeper with my buddies at Alldata.com and discovered that there are a number of possibilities that cause this racket.

The possibilities are:

  1. Drive belt/s
  2. Drive belt tensioner
  3. Alternator
  4. Power steering
  5. Air conditioner
  6. Water pump

Now, I’ve mentioned in the past that some technicians will apply the “Shotgun Approach” to diagnosis and in your case Doug, you’re looking at a significant drain connection to your wallet if anyone were to apply this approach, so I’m going to give you some ammo to use when you visit your repair shop.

To start the diagnostic process, the easiest thing to do is to rule out the drive belts. This is usually accomplished by spraying water on one belt at a time. If your engine is like most, you will have three drive belts on the front of your engine. If the noise changes or goes away at the exact time you spray a particular belt, that belt is the problem.

If, on the other hand, there is no change to the noise while you spray, then the problem is mechanical. This is where a talented technician will pull out a stethoscope and test each driven component for noise. Typically, the stethoscope tip is placed on the component adjacent to the bearing/s. This is a fast method of zeroing in on the suspect part. But this only tells the tech that a noise is emanating from the component or surrounding area, it doesn’t tell that tech exactly what is making the noise – often the assumption is made that a bearing is gone, but that is not always the case. There could be an alignment issue.

Once the noise has been located, inspection should focus on that device’s mounting, as well as an internal diagnosis. This includes checking the alignment of all pulleys (sheaves) with respect to the drive belt. The Nissan Shop Manual contains this procedure. This must include the belt tensioners. According to a Service Bulletin I found (# NTB10-002, dated January 12, 2010), the tensioners are a focus in this process. The TSB goes on to illustrate the amount of radial and axial play that is permitted for normal service. Any amount of play outside these numbers condemns the tensioner and will require replacement. Doug, your engine has the option of two different designs. You might have an automatically adjusting tensioner or you could have a manually adjustable type. This will have to be determined by the tech at the time.

The remaining driven components are somewhat self-explanatory; except the alternator. The design of alternator on this engine family has one intricacy that is uncommon; and that is a one-way clutch installed at the drive pulley (or sheave).

There is a test for this clutch that can be performed while the alternator is still mounted on the engine. The drive belt must be removed and the electrical connections to the alternator must also be removed. The tech must prevent the internal rotor from moving using a screwdriver wrapped with a cloth rag. He/she should try to rotate the drive pulley clockwise – viewed from the front. The pulley should not rotate. If the clutch is working properly, the internal rotor should be locked to the pulley and if the rotor has been secured with the screwdriver/rag combo, there should be no rotation. Next step is to rotate the pulley counter-clockwise – it should rotate freely.

If the pulley rotates in both directions, the clutch is defective and the alternator as a whole must be replaced. In this case, a stethoscope test may have picked up a sound, but as I mentioned earlier, the noise may not be a bearing, in this instance, the problem is within the one-way clutch of the alternator.

There you go Doug, take this info to your shop. It should help in the decision to keep the shotgun holstered.

Send your auto maintenance and repair questions to globedrive@globeandmail.com

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