Rumble in front left of 04 Prius

Well, if it's a wheel bearing, I'd assume that it would be speed sensitive, i.e., as your cruising speed increases the pitch of the rumble gets higher. That might be a clue.

Come to think of it, ditto with an electric motor bearing (depending on which MG might have the problem). Isn't MG 2 directly joined to the PSD? that'd mean that it, too, would be speed sensitive...right? MG 1 isn't though...so this might help differentiate between the two and where the problem might lie.

Someone who really knows these cars could tell you, but I can't.

Diagnostically speaking, with a conventional car, I'd try coasting in neutral to see if stopping the rotation of some of the parts in the transmission helps...but I honestly don't know what effect, if any, this has on the Prius with its PSD.

Also, technically, there is no CVT in a Prius; it's a power split device which is based, in part, on the planetary transmission such as found in a Model T Ford.

Based upon your observation that the rumble gets a little louder when you turn right, I'd guess that it's actually coming from the right side of the car...and the problem is the RF wheel bearing.

OR...

Second guess is that there's a problem in the PSD, and the differential action caused by turning is creating the noise. Hope it's the first one!!!!!
[smile]

 

<div class='quotetop'>QUOTE(Devil's Advocate @ Dec 27 2006, 03:22 PM) [snapback]367395[/snapback]</div>

Hear it only and not feel it in the wheel or floor?

Tried a rebalance of that wheel? Ask for a rebalance and report how far out it was. Hopefully you rotate periodically (good time to rotate!)
Inspect your CV boot - good shape? not leaking grease?
Inspect suspension bushings - still rubber in there? Not cracked or crumbling? Free play?
Push down hard on that corner of the car - rebounds the same as the other corner?
Tire wear normal? If not, a loose steering rack ball joint can allow a wheel to act like a caster wheel on a shopping cart and this may appear as a rumble.
Inspect all joints - jack up that corner try to turn wheel back and forth any free play? Do same with top. Push and pull bottom of wheel in and out, any free play?

I'd suspect ball joints first, CV joint/boot next (can be bad even if looks ok), wheel bearing and motor or CVT last.

 

Jack up the FL wheel and try to tilt it top-to-bottom. If you feel
any play, chances are it's the bearing.
.
_H*

 

I'd look for oil stains under the car, to see if that provides any clues to a part that failed.

For example, there is a shaft seal where the left-hand half shaft leaves the PSD that has been known to leak. Mine did, but I caught it early. I've read four other accounts on the forums where this seal is suspect. It's hard to see the seal, because the inner CV joint blocks the view. But the oil stains under the PSD, along with following the path that fluid woud take when subject to gravity and wind, provided the clues to diagnose.

Perhaps there are some similar type of clues awaiting your or a mechanic's visual inspection that will help pinpoint a part or seal failure that by and by caused the rumble.