It's my 1998 XK8 coupe. The first problem is a noise coming from the right front end (I think). The sound is like a tire going over one of those rough white lines on the highway or like water splashing against an inner fender well (though not as loud). I see nothing rubbing to cause this noise. Tires are in good condition, I notice no loss of power when the noise occurs. Possibly a wheel bearing?

The second problem is a rattle in the center section of the dash; it happens only when the weather is cool--less than 40F--and when going over a bump--the more severe the bump, the louder the rattle. I used to be able to press on the dash around the A/C vents to quieten (but not eliminate) the rattle, but not any more.

Are there any usual suspects? Thank you.

 

Difficult to diagnose noises over the internet but two thoughts: the early cars, '97 - 98 did have many front axle bearing failures that resulted in upgrading the axle diameter and bearing for the '99 model year, and, common issue with the AC duct separating from the dash just enough to make noise. The ducts are only attached with double sticky stuff which eventually gives up. I have the same problem and it is only noticeable when driving slowly over uneven pavement. Just not bad enough to tear the dash apart to address it.

 

If not the demister vents, my rattle in the dash was corrected by tightening the dash bolts under the dash midrange speakers...if that MY had premium stereo option.

 

I know you said that your tires are good but you might look for some "feathering" of the tread block where the front edge of each block is a bit lower than the rear of same. I had that occur on one of my big tires on the R and was told that this is very common. It was only on one tire and just on the outer blocks. Tire is still good but gives a bit of a 4x4 sound at some speeds.