Chirping, again

Some time ago I posted about a very annoying chirp/rattle in my 2007 Prius. All sorts of ideas were tested but nothing worked. And, over summer, it didn't seem as bad. This is a key point as now, with colder temps settling in, it's back and worse than ever. But, I can now offer additional details:

• The noise comes from the general direction of the front right corner of the car but is not inside the cabin.

• It happens when the temps go below 48 degrees.

• When the car itself, not the engine, warms up to ambient temps it goes away. As when parked in the sun during the day.

• It happens no matter the engine mode: Electric only, ICE only, combo.

• It happens when coasting down a hill in neutral.

The belt has been replaced, moot since it happens when in electric only. This week, after waiting for the temps to drop in Denver, I took it to the dealer, left it overnight and went down first thing for a test drive with a tech. You know what happened: barely heard the noise despite temps in the low 40s. But when coming home up I-70 -- I live at 8,000 ft -- it came back. ARRGGHHHH!

So I'm circling in on some kind of diagnosis but could use your help. Unfortunately, there are no other Toyota dealers high enough to prove the latest point. But, what could it be that would require both high elevation and cold temps to kick in? Gas/fluid? Any lines up there? Is the shock/strut gas filled?

I'm trying to get this figured out before I'm out of warranty -- at 32,000 miles now.

Thanks!

 

How do you know the source of the noise is not within the passenger cabin?
and When you open the windows, is the sound louder vs. when the windows are closed?

Very slightly louder when driving close to a wall or hill on right side. Can not localize when riding in passenger seat and leaning forward or down into the footwell. Happens whether or not heat/air/fan on any sort is on or off.

Regarding your reference to a "belt", are you referring to the serpentine drive belt that spins the engine coolant pump?

Yes.

Is the noise a chirp or a rattle?

Chirping. On rare occasions will increase when ICE is revved as in going uphill or accelerating through mid-range RPMs. Does this only when very cold.

And, add: Is not affected by speed or turning.

 

Update: Vehicle is back at the dealer who think it's located between the firewall and cabin, but can't get a run of enough cold weather to fully diagnose except for quick test drives in the morning. Hey, at least they're trying.

 

Well, the problem appears to be fixed. The dealer removed and reassembled the front right headlight assembly. Last night, driving home in a chilly 16 degrees, no chirp. Finally!

This is a case where the dealership end up being the good guys: they decided early on that they were curious enough to take this on and not let go, like a dog with a bone. Remarkable, given that this was a cashless warranty repair. I think one of the keys was patience on everybody's part due to the peculiarities of the situation. They were trying to get the car back to me before being certain despite a weather warm up. I said no, wait until it's cold again so we're all comfortable with the result.

I sure am.

 

elitry,

My symptom was very specific to the vehicle moving regardless of any other variables (braking, turning, ICE, stealth, cabin heating/cooling, etc.) wherein the body of the Prius was 'in play'. Per the dealership notes, "...removed the headlight assembly and noise stopped. Lubricated all contact points on the headlight assembly and reinstalled. Noise did not come back."

Good luck.