Isolating the Source of a Whine (1 Viewer)

[bert brown]

I have a 1995 GXL 80 Series, 4.2L normally aspirated diesel. When accelerating and as the rpm passes thru 1800 - 2000 rpm a whine emits from the engine bay (I think). The whine occurs independent of speed & gear and is related to engine speed. When stationary and with engine running thru various speed ranges don't seem to get the noise.

Sounds to me like a bearing on the way out - but the question is which one (alternator, power steering, idler pulley, timing belt pulley, air conditioner etc etc). Don't want to isolate the fault by driving to failure and discovering the problem out in the sticks & getting stuck !!

Anybody have any ideas or techniques about how this can be diagnosed?

BTW - vehicle has travelled 150,000 km.

Thanks in advance.

Bert

 

[Safado]

Bert,

Are you sure it's not from the muffler? Some on this board have had this problem.

If indeed it is from the engine bay, can you reproduce it in Neutral? If so, get someone to help you by giving it gas until you hear the whine. If you can't locate it easily, a small metal pipe or rod is what I use. Carefully place one end of the rod on each device you suspect and put the other end to your ear. It will amplify the sound and you will be able to determine it faster that way.

BTW, some autopart stores will sell devices specifically for this that look like stethoscopes with a long piece of thin tube attached.

Good Luck

 

[IdahoDoug]

You"ll definitely get on your neighborhood watch list for this one, but garden hose also transmits sound readily when one end is pressed against each suspected component in turn. Buy a cheap one or use an old one and cut it to the shortest length that will reach out the window, under the vehicle and into the engine bay. Use duct tape to hold it against each suspect in turn, while the other end is against your ear. For the full "Road Warrior" effect, use duct tape to hold it on the B pillar so you can drive down the street leaning against it and rolling your eyes....

No joke - this works, but the special effects are up to you.

DougM

 

[Tooth Fairy]

I usually just find a straight section of road and set the cruise. Actually I've only thought about doing that.

 

[Beowulf]

Bert,

I have heard that you can pick up a pair of those cheap hand-held FRS radios and use them for diagnosing noises. Similar to Doug's suggestion, you could use a cheap plastic microphone like they used to throw in with PC sound cards. Creative use of duct tape, tune to the same channel, and off you go.

-B-

 

[rgmax]

I have a weird whining noise that I thought was coming from the engine bay. Loud whine on acceleration above 2k.Ireplacing all the belts, checked the pulleys. etc. still had the noise. I gave up and took it to the dealer, the tech almost pulled his hair out until he finally diagnosed it as a loose baffle in the muffler.

 

[bert brown]

Thanks everybody - like the hose/ radio idea !! Have tried listening with the hose to the various suspect bearings while the vehicle is stationary and @ the 2000 rpm - no breakthroughs though - am beginning to suspect the muffler baffle suggestion may be the correct one.

Thanks for the help.

Bert