WDBEA30D

Yesterday, I noticed a sound coming from the engine compartment while driving in areas where the noise generated by the car would reflect off nearby objects--going down alleys, between cars, etc.

The noise--which I would best describe as a somewhat metallic light "skiffling" sound--would increase in rhythm as I increased engine rpm (even in neutral). However, under power, the sound either disappears completely or is inaudible. I'm most likely to hear the sound again as I coast to a stop and engine rpm drops toward idle. The sound isn't constant, sometime going away and then coming back as the car is just sitting there idling.

Today, after I drove the car to work (not really noticing the sound at all), I opened the hood and tried to locate the source. I narrowed it down the the pulley located immediately BELOW the power steering pump [pulley]. Is this the water pump? Visually, the light-colored metallic part on the leading side (relative to the layout of the car) of this pulley appeared to be wobbling ever so slightly. What do you think? If this is the water pump, could the bearings inside be going bad, causing this metallic piece to wobble just a little and generating the sound?

shdoug

Directly below the PS pump pulley is the AC Compressor. Is the sound only when the compressor is running? [For the benefit of all, there is a magnetic clutch on the front of the compressor that causes the compressor to rotate with the pulley when power is applied.] It's normal for the compressor to make a little noise when it's engaged. If you turn off the AC, it should not make any noise. When it engages, you should see the fluid in the sightglass fill and clear. (It appears clear because it's completely full) If you see liquid running through the sightglass continuously while the compressor is running then you are short of refrigerant, unless it's very cool outside. As long as the refrigerant charge is correct, that's about all you can do.

Your car uses R-12, which is no longer made in the USA or imported, thanks to the EPA. It is hard to come by because all that is left is what has been recycled. They use it like crazy in 3rd world countries so it doesn't do much good to ban it here, but that's another story. If the charge is low, It may cost $50-75 per pound to top it off, assuming it doesn't have a significant leak.

The compressor in a car this size has the capacity to cool a 1,500 square foot house, so it's going to make some noise when it runs. If the discharge temp is below 50 degrees when running at maximum capacity and driving down the road, it should be fine.

WDBEA30D

Wow, thanks for that--I didn't think of the A/C compressor when I ran through the metal list of serpentine belt-driven accessories. It IS directly below (maybe 4 inches) under the P/S pump, which I recognize because the cylindrical P/S fluid reservoir is just above the pump. So it must be the compressor. Plus this thing seems more or less attached to the side of the engine, whereas I thought the water pump was INSIDE the engine.

HOWEVER, the car still makes this noise even with the compressor off ("EC" button selected on climate control). That metallic piece (apparently that magnetic clutch you refer to) keeps turning anyway even with the compressor off, and that appears to be, IMHO, where the noise is coming from. I can "feel" the compressor kick on when I hit the middle climate control button, so I'm sure it's working. It does need refrigerant for sure, though, as the only time it blows COLD air is when it's relatively cool outside--like in the evening. Merely lukewarm air on hot, 90-95 degree days.

But back to the noise--does it seem likely that the A/C compressor or its magnetic clutch would create this sound?

shdoug

It's possible that there is some "crud" in between the clutch plates making a quiet scraping sound, or the plates themselves could be rubbing a bit. But if this is the case then the noise would go away when the compressor is running because the plates would lock together.

Here is a diagram of the components. If your water pump is like mine, it doesn't look like a water pump. It's at the top center. You might be hearing the idler (tensioning) pulley developing a bad bearing.

I added a diagram of the compressor. Looks painful. You might want to just drive with the radio on so you don't notice it. I find my stereo covers a multitude of sounds.

delija

You need to replace drivebelt tensioner, i am not sure if this is correct name for it. Easy fix!