Howdy everyone... first post here; enjoying the information on this great site.

I recently picked up a used '07 Caravan SXT. It was examined by a mechanic before the purchase and is overall in very good shape (a lease return with about 81400 kiolmetres on it).

I recently became aware of a problem which, as you'll see in a moment, was not possible to detect when I was evaluating the van.

Any time the engine is completely cold when I start it up, there is a brief but fairly loud grinding sound as the engine revs up and down during the start. Once it's running, I no longer hear it while the car is at rest, even if I press on the gas pedal.

When I drive off, I hear the sound intermittently for about 2 more minutes, and then it's gone. No matter how I drive (fast, slow, completely at rest, whatever) the sound is no longer heard, even if I kill then engine and restart it. It will return, however, if the engine is allowed to cool down completely and is restarted cold.

The sound is quite brief, about 1/4 or 1/2 second long, and comes from the driver's side in front, as best as I can tell from within the car. When driving, the rattles are highly intermittent and don't appear to coincide exactly with gear changes in the transmission, though I am more likely to hear them when the engine RPM is higher. The volume of this sound is always loudest during engine start; it's quieter when I'm driving.

What puzzles me is that the sound is heard both when the car is at rest (i.e. during a cold start) and when driving. It seems that something is being jerked loose during a cold start, and then it settles down after a minute or two and behaves itself.

Any suggestions as to what this might be? I will, of course, take the car to my mechanic, but since the sound is only heard briefly during a specific set of circumstances, I'm concerned the mechanic might not be able to hear it unless he leaves my car sitting around all day to cool off.

Help would be much appreciated.
BM

 

Just to clarify, you are hearing a "grinding" sound as opposed to a "whine"? Grinding would be metal on metal, whereas the whine would vary in pitch with the speed of the engine. This van has a weak power steering pump which when cold does tend to whine for a minute or two on startup. Does turning your steering wheel have any effect on the noise?

 

This is definitely a grinding noise, not a whine. Moving the steering wheel around doesn't make the sound happen; it occurs during startup and when driving, but doesn't coincide exactly with anything I'm doing, so far as I can tell.

I've heard that the power steering system can sometimes cause a grinding noise during start, so that might be worth investigating. But any other suggestions would be welcome.

 

Any chance your hearing the clutch from the A/C compressor? It engauges with the "defrost" if you turn the heat up on a cold morning.

Maybe get out one morning prepared to look in there while someone else is starting it. Should be a quick diagnosis.

Hope this helps!

 

Don't think that's it... I have the heat turned on, but not set to any of the defrost settings. The compressor shouldn't be running in this case, right?