Growling sound? Better check your bearings

Hey there, time traveller!
This article was published 18/04/2008 (6548 days ago), so information in it may no longer be current.

QUESTION — I have a 2002 Honda Odyssey Van in excellent condition and good working order with 170,000 km. Last winter I noticed a soft growling noise which sounds between the speeds of 70 and 80 km/h. It doesn’t sound all the time, but when it does it is always between 70 and 80 and the rpm needle seems to fluctuate up and down briefly but not every time. I drove approximately 100 km at this speed (between 70 and 80) today and it only happened three times during that period. The dealers have checked this and don’t know what the problem is. Can you give me some advice?

ANSWER — Often, a soft growling noise on a higher mileage engine is found to be coming from one of the bearings driven by the engine’s serpentine belt. It could be coming from the water pump, alternator, air conditioning compressor or an idler or tensioner pulley. You would think that a bearing noise would be continuous, but when they are just starting to fail, the noise can be intermittent, changing with loads on the engine and serpentine belt. Wheel bearings could also cause this sound, but would vary with side to side loads on the vehicle and over a wider vehicle speed.

The tachometer fluctuation could be unrelated, but if the alternator bearing was beginning to fail, it could cause the alternator speed to suddenly change and this could affect the electrical system and tachometer for a brief time interval.

Access to the front of the engine isn’t great, but if you listen to each rotating part with a mechanic’s stethoscope, you may be able to locate a faulty bearing. It will sound noisier and rough.

QUESTION — I have a 1997 Ford Ranger XLT automatic. It starts easily and runs properly until the engine warms to normal temperature. After that, whenever I slow down, come to a stop, or shift into neutral, the engine starts to surge and sometimes stalls. There is no noticeable problem while driving. The “check engine” light has been appearing and disappearing for the last year or so (presently on- Code P1443) but the engine surge while idling has only recently appeared.

ANSWER — Let’s look at the code problem first. Code P1443 is an Evaporative Emission Control System error. The vehicle’s computer tests the integrity of the gas tank seals and all the connecting emissions hoses by placing a vacuum on the system while the engine is running. If a vacuum leak is detected, then the computer sets a code and turns on the “check engine” light. If the system passes the test three times consecutively, the light will turn off but the code remains.

Your vehicle has the light on and off, so the problem is intermittent. Anything that could cause a vacuum leak into the fuel tank could be at fault, such as a loose gas cap, leaking gas cap seal, loose connections at any of the hoses to the fuel tank, fuel sending unit gasket leak, or a fault with the solenoids controlling the air and vacuum in the tank. These leaks can be difficult to locate. Some repair shops use a smoke generator, filling the tank with smoke and visually checking for external smoke leaks. The gas cap seems to be a more common source of a leak.

Now to the surge. The engine is surging because the computer is moving the idle air control (IAC) valve to try and control idle speed. If the engine starts to die, the computer opens the IAC to increase idle speed. If the engine is idling too fast, the computer closes the IAC to slow it down. Normally the IAC is sitting in a position where it can either open or close, but if there is an engine problem, such as a vacuum leak, then the computer moves the IAC to the fully closed position and it can’t react as fast. This causes it to surge as the computer overcompensates.

There are two things I would look for. First, clean the throttle plate and bore of any gum deposits. A calibrated amount of air flows past the throttle plates at idle and if this area is gummy, then the amount of air entering the engine is incorrect. Second, look for a vacuum leak. I think this will be where you will find the problem. The vacuum leak could be caused by a cracked or loose hose. Pay special attention to the hoses for the evaporative emissions system, as this is where the Code P1443 would lead you.

Jim Kerr is an experienced mechanic, instructor of automotive technology and member of the Automobile Journalists’ Association of Canada. You can e-mail questions to Jim at the address below.

kerr.jim@sasktel.net