Whirring Noise on engine shutdown

[Giltos]

Heya guys,

Interesting one for you all!

Had a small noise for a while, which has now turned into a bigger one !!
On turning off the engine, there is a noise, hard to describe appropriately, but sounds like a wurr as something is spinning down, for approx 3-5 seconds.

Originally we thought is was the turbo about to go, but last night might have narrowed it further, interested in your thoughts and see if anyone has experienced it.

Touching the back of the alternator when turning off engine could feel the vibration through the casing. At back of alternator looks to be some clutch or bearing which does spin for 3-5 seconds and is making the noise.

The alternator was replaced about a year ago, and is non genuine. Thoughts?

 

[nismo4x4]

sounds like alternator to me...i had same issue

i posted you tube of the sound...does it sound like this

http://www.youtube.com/watch?v=kcFrUUO5IFk

 

[Giltos]

Slightly different
When its running all fine, no squeaks, squeals or noises. Only when turn off, and its different noise as it winds down, not a real metal on metal noise, but i suspect the same problem.

Can they be rebuilt? or Am I up for another Alt ?

 

[nismo4x4]

mate there $350 on ebay which is pretty cheap with 5 years warranty and a piece of piss to change urself...

 

[batcho]

Sounds like turbo to me. Try run the car and have someone close to the exhaust exit when you turn it off. if its louder there it will be the turbo and its nothing bad they just spin after the motor turns off .

 

[longy509]

Are you sure it is coming from the engine bay my fuel pump makes a similar noise to i hear it when i turn the ute of and it also just randomly come on

 

[Iceman]

Mine make a niose as well. Sounds like a small electric motor running for a couple of seconds. Maybe closing throttle or egr butterflies? Does sound like something 'closing off' will have a listen next time im in truck.

 

[bods]

The egr valve cycles on engine shut down, so that could very well be the noise you are hearing... Although that is on the opposite side to the alternator

 

[clawrence]

I know exactly what you mean. My 09 D40 groaned every time I turned it off. I drove it around like this for about 6 months (the local Nissan dealer told me it was normal!), before I finally replaced the alternator. That was it, the groan was gone and never came back.

 

[Giltos]

longy, definately from alternator now. Got a few people round and we started/stopped many times, traced to vibrations at back of alt.

Iceman, noise is getting worse, its like a bearing running dry or something similar.

clawrence, yes i think its alt related. Have taken it to a few different people over the weekend and consensus is something at back of alt. Need to take it out today if i get time and check. Will report back.

Thanks guys for you thoughts

 

[Iceman]

Yeah mine is defo egr valve. Maybe upset due to blocked egr? He he he...
Sounds like you have a dodgey alternator unfortunately.

 

[Giltos]

All sorted, turned out to be the fan belt tensioner a front of alt. Took off the belt and turned by hand, you could feel the grind.

Just picked up a new one here http://www.precisionintl.com/Part.aspx?ID=71277&EID=2533322 and will fit on weekend.