Grinding / scratchy noise from engine compartment

91pathfinder · Jan 29th, 2007, 01:43 PM

Just recently, I am consistently getting a grinding / scratchy noise (not sure what words best describe the sound I am hearing) that is coming from the front of the engine near the pulley. Location would be located center pulleys, I can guess related to the fan or fan clutch assembly OR other pulleys in that vicinity.

From a cold start (ambient around 20F), I warm up the vehicle for 1 minute. I start a drive that is takes me 25mph. I start to hear the noises about 1/2 mile into the drive. The noise gets louder and the noise pitch is related to engine RPM. If I park the car 1 mile later to diagnose the noise by lifting up my hood, I can hear the noise at idle too.

If I continue to drive (i.e. 4-5 miles later), the noise seems to go away or the noise is not noticeable anymore.

Can someone advise on a few things?
- How do I better diagnose where the noise is exactly coming from?
- Has anyone heard of this issue before? If so, what has someone done to fix this issue? (i.e. what components needs to be fix or replaced)
- What will happen if I continue to drive with this issue?

Any help is greatly appreciated!

*************************************

Just a background my vehicle.

I currently have 122,000 miles on the vehicle. I have owned this vehicle since new, so I know the history behind this vehicle.

All the belts (including timing belt) was replaced 2 years ago at 110,000 miles. The water pump was changed at the 110,000 mile timing belt service. I have not serviced the fan or clutch before. Starter, alternator components are still original.

dvdswanson · Jan 29th, 2007, 03:07 PM

is the fan hitting the fan shroud? how are the motor mounts? are any of the pulleys loose?

91pathfinder · Jan 29th, 2007, 03:55 PM

- fan is not hitting the fan shroud
- motor mounts look good
- pulley's loose? I'll check that later tonight.

littlefish · Jan 29th, 2007, 07:55 PM

Have you ever replaced the timing belt idler? Does it sound like it is coming from the center front of the motor? These things do go bad.
Best of Luck..Littlefish

91pathfinder · Jan 29th, 2007, 09:35 PM

Littlefish -

Thanks for your reply.

I have not replaced my timing belt idler. Where is the part located? When do you typically need to replace the timing belt idler? How do I better pin point the noise to ensure it is my timing belt idler? What type of failures can occur if the timing belt idler get worse? Sorry for all these questions.

Yes, the sound does come from center front of the motor. It is quite hard to distinguish where the sound is coming from exactly (i.e. when you look down the center front of the motor, there are a few pulleys along the vertical axis).

Zilverado · Jan 29th, 2007, 11:59 PM

I've posted this before, but it's worth repeating - could help you out.

When it comes to tracking down these types of noises, I like using a mechanic's stethoscope, quite cheap at a parts or tools store. Same idea as the medical version, just with a long metal end instead of the circular pad. You just stick the ends in your ears and then place the other (long metal) end on the various components to try and pin point the noise (just don't touch a rotating pulley

I find this has worked for me a number of times when I'm trying to find the source of a noise. Sound travels well through the steel and aluminum parts on the engine and is easily transfered into the stethoscope.

Just a thought...

littlefish · Jan 30th, 2007, 10:59 PM

First I suggest buying a Chilton or or other service manual and begin looking at your engine from the drawings/photos. The timing belt idler pulley is located behind the fan blade with a big flat cover that completely surrounds the timing belt and pulleys. If a timing belt idler bearing seizes, it is a major item to repair. Unless you have plenty of tools and time, take it to a good shop. Unless you are fairly experienced, I would not recommend doing this yourself. Also Antifreeze is not a pleasant liquid to deal with. Not the best thing to get on your skin if you get my drift. Best of Luck...Littlefish

stephank · Feb 9th, 2007, 06:00 PM

I have the same noise. I am pretty sure it is the drive belt idler-pulley.
My '95 V6 does not have a Timing Belt idler. The timing belt runs around both cam pulleys, around the tensioner then around the crankpulley. No timing belt idler.

**88pathoffroad** · Feb 12th, 2007, 02:23 PM

I'm sure he just got the terms confused. Idler, tensioner.