Help! I am not sure if there is something wrong with my engine

That's the sound of an engine chuckling for you running 3000 mile synthetic oil change intervals. j/k ound:

 

I understand that the sound occurs at all times that the car is in motion, regardless of whether you are in N or in D. I also understand that the intensity of the sound (and the frequency?) increases as your speed increases.

If my understanding is correct, then I would say that the problem is likely to be a wheel bearing or maybe a tiny rock stuck in your front disc caliper. Your car is probably still under the 3 year / 36K mile warranty; if you can demonstrate the noise to your dealer's service writer it would be reasonable to take the car in and let the service dept figure this out. Good luck.

 

Next time, turn off the air conditioner if that was on. Probably not the cause, but too easy to eliminate if it is on.

There are two basic rotational frequencies in the drive train, the engine rpm going into the planetary gear and the wheel related rpms after the planetary gear. When you hear it again, try to see if it follows the engine rpm changes or the car speed changes.

 

Side topic: Why change synthetic oil at 3,000 miles when you are doing long distance trips? If you were using dyno oil and doing primarily short trips (few miles per year) a shorter interval might be justified, but what you are describing is a waste of oil, money, and time.

On topic: I don't see what 17 hours straight run time would have to do with it. According to you the sound is tied to velocity (tire rotations), not the engine.

First thing I would check is the tires, rotating front to rear. If the sound switches to the rear then you know it is the tire. Second thing I would consider is tire pressure. You indicate you are running stock pressure. It might be worth trying a higher pressure, still within placard limits to see if it alters the sound.

Other rotating parts that operate at drive line frequency are of course a concern so the bearings and rotor/caliper assemby would be suspects. Demonstrate the noise to a dealer service writer/mechanic. (Ask to borrow one for a few minutes to demonstrate while it is doing it--I've done that before with various vehicles.)

 

I agree - try to confirm or eliminate tire noise as the issue.

 

If it is a bearing or joint problem it can quickly become dangerous. Take it to a dealer.

 

Could be a bearing, could be something else. With sealed bearings, a lot of the old tricks to check bearings (Jack up one wheel at a time, wiggle the wheel to see if it feels "loose") are iffy and may not apply

Compare the noise to another Prius. Get it taken care of. If it is a bearing, they tend to go quickly

 

We routinly use our 08 Prius to go back and forth from Pa. to Fl. Never noticed any weird noises even with 70k on it now. Do you still have the original tires?

 

Hey GasSaver, I will offer my assistance if you are interested... I am in the West Palm Beach area and would have no problem meeting up with you for an extended test drive to attempt to identify the noise you are hearing. If it turns out to be something covered under warranty, I can even help arrange an appointment at my shop to get it taken care of. If not under warranty, I will be happy to offer my two cents worth on getting it straight.

Send me a PM if you are interested.

 

Just read your offer...way to go Bear68 :rockon:

 

Hi All,

Tire or bearing are my guesses. At that kinda service both are running hot. If your not running 42/40 PSI on the tires, they might get hot enough to be at risk for internal delamination over a 17 hour trip. My hydroedge tires make that noise, but its not audible, except during low-speed glides from the driver's position. And they have actually gotten quieter with wear.

It could be a "spun" bearing too. The bearing is pressed in. If it got real hot and froze momentarily, it could have spun in the hub, and ground the hub clearance loose. Now it spins regularily in the hub.

Of course there are the other usual suspecs. Have you kept up with inspections of CV boots? If a CV joint is dry - their ya go. If that happened at the beginning of one of those trips, the CV joint would be bad bad by the end in hot weather.

 

I have the same issue only not as bad on my 07. Its your tires. I just had my fronts re-balanced and they are not doing it as bad but still have the low freq woo woo as you put it. Keep in mind the stock Integritys are really an awful tire. Really poor. Almost as bad as Wrangler RT/S's.

Lets prove it:

Drop your tire pressure on all tires to 28 lbs for a test. Take it for a ride. I bet the noise either stops or is much less. BTW, my Prius and alot of other Prius's come delivered with about 28lbs of pressure. Makes for a nice soft quiet ride (until they wear) but mileage will suffer. Good Luck!

 

The sound you demonstrated above sounds like a slightly warped rotor. This would give you a ch-ch-ch sound that would increase with speed. A warped rotor in a Prius would be harder to detect as the mechanical brakes only come into play at lower speed. In a non-hybrid car the mechanical brakes are always in use so when you press them at high speed you get both a vibration and pulsing in the brake pedal due to the warp in the rotor, no matter how slight the warp. Since the mechanical brake are only used at low speeds (i.e. 7 mph and lower & in emergency situations) the vibration and pulse would be very hard to feel at that low speed. Take the car to a mechanic,put it on the lift with someone in the drivers seat, have him remove the front wheels, the driver should put the car in drive and accelerate slowly. You should both see wiggle of the rotor and hear the noise you describe, if this is your problem.

 

Ah ha ha ha. I had a set of RT/S on my Explorer. Those tires suck. I finally ditched them not because of the tread depth but because I was tired of listening to the roar.

 

You can see how well this remote diagnosis is working. Take it to a dealer and hope that it's not a bearing or joint problem.