Whine on acceleration

[timthetortoise]

My apologies if this has been asked to death, but Google didn't turn up anything too informative so if there's a thread or URL I should look at, please kindly direct me to it.
I bought my first Explorer today. It's a 1998 Sport 4.0L V6. Everything is great on it, except for one possibly serious problem. When I get above 30 MPH and step on the gas (even lightly), I get a whine that sounds like it's coming from the tires. As I speed up, the whine gets higher in pitch and by around 75 it's not as noticeable (though I know it's still there, just out of my range of hearing). I'm just wondering what the possible causes of this would be. The guy who sold it to me said he had the bearings replaced just recently. However, while going under 10 MPH, I have noticed a little bit of noise that sounds very similar to wheel bearings going bad (light, intermittent grinding). I haven't had a chance to check the power steering fluid yet, so that might be a cause - but I'm just wondering about what causes I should be trying to track down.
Keep in mind I'm by no means great with cars so if it's something that the average Joe wouldn't be able to look at and go "oh, that's bad," please give a little bit of guidance as to how I might go about figuring out what the real problem is.

Thanks in advance!

Tim

 

[IZwack]

Right now, from your description, this really could be anything.

You did mention "grinding" so I guess first easy thing to do is jack up one corner (of the vehicle) at a time and check for any up/down side/side "play" in the tires.

 

[timthetortoise]

Well, I checked the bearings and the passenger's side feels like it has a tiny bit of play, but not enough to make me think that the whine is from bearings (though I will probably be replacing them in the near future). I found a thread that had a similar problem and one guy said he fixed it by replacing the idler pulley. At $20, it's about the cheapest part to try.

 

[Glen4X4]

Does the whine go away when you leave off the accelerator?

 

[timthetortoise]

At first I thought it did. However, it's only the consistent whine that goes away. If I listen very closely I can hear a "wonk wonk wonk" at times (but it seems like it disappears 80% of the time when I left off the gas)

 

[Glen4X4]

I was going to say it could also be the IAC thats making the whine noise too if it goes away while off the accelerator. But that don't explain grindage.

 

[timthetortoise]

Grindage may be a separate issue completely. I'm fairly convinced it's the bearings (guy who sold it to me took it to someone to get the bearings done, but I think said guy may not have actually replaced all the wheel bearings - just ones that were causing problems at the time). Is IAC Idle Air Control valve?

 

[Glen4X4]

Its right on the top uhh...http://img74.imageshack.us/img74/574/xpic2sn4.jpg you can see its gray with a black cap on the side.

 

[Glen4X4]

only two bolts hold it on, its worth a try to clean it anyway. Just get electrical cleaner or some use carb cleaner spray in there see if any black comes out, i also swabbed it with a qtip to get the gunk out.

 

[timthetortoise]

Ahhh, cool. I'll run out and check it right now. Anything I should be looking for on it/is there a way to salvage it or is it a matter of if it's toast just replace it?

 

[Glen4X4]

It can be cleanable, some people haven't had luck cleaning though and just bought a new one, the price for a new IAC depends on the motor you got (OHV or SOHC)

 

[timthetortoise]

Hm... it looks a bit dirty. $50 for one ain't bad. So, I'm going to be replacing the idler pulley, serpentine belt (some weather checking on it), IAC valve, and will be taking it to the mechanic that did the bearings (he claims that he replaced inners and outers and warranties his work, so I'm going to bring it up to him tomorrow to have him take a look). Hopefully one of these things fixes it! I also read about pinion bearings causing this, but don't have much experience with differentials, any chance it could be bearings or seal?

 

[Glen4X4]

I couldn't answer that

 

[timthetortoise]

New development.
I just took it for a 10 mile city drive. A couple times, the whine kept going as I was coming to a stop and once stayed even while I was stopped. However, when I made a right turn from both of these, it stopped (but still goes while accelerating 30+). Power steering pump mayhaps?

 

[Glen4X4]

Is your truck 4X4 or 4X2?

 

[timthetortoise]

2wd

 

[Glen4X4]

Ok then, im not sure on the build of those spindles. I think though (not 100%) your bearings are held on by 2 nuts and can be tightened with the proper socket or can take a flathead screw driver and hammer to tighten the nuts. (if I'm right your spindles are like 4wheel ones in 91-94 explorers) and thats how they're tightened. The way your talking, I think its the wheel bearings.

 

[timthetortoise]

Rookie mistake. The whine that was still going while I was stopped was the result of an under-tightened IAC. Oops.
The wheel bearings will be checked out in about 11 hours. Hopefully I can eliminate them as a culprit.

 

[Glen4X4]

So the whine has went away since you tightened the IAC more?

 

[timthetortoise]

Only the secondary whine that wasn't there before. The whine on acceleration persists and after reading some more last night, I fear it's the pinion bearing. Hopefully the guy who's going to be looking at the bearings is able to work on differentials too and can check it out.