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I did a search of the forum and found no mention of this. I have an 01, classic Prius with 36K on it. Have done the 6 month checks religously. Have experienced, since about the 12 month check, a strange noise from under the hood. It strated out as an intermittant chirpping sound and gradually grew into an intermittant screeching sound. It could happen rolling or not under electric or under gas or both power trains.

Six weeks ago, at my 44 month check, the service mgr finally heard it as did everyone in the garage. They had the car for two, 4-5 day periods (giving me an Enterprise car for a loaner). They pulled the transaxil and replaced. The sound went back to the chirp but now is more frequent. Car goes back to dealer (a major SF bay area player) next week. They still have no clue. Any ideas out there?

Thanks, Phaon
 

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If I understand you right, the sound sometimes occurs when the car is not moving. If during that time the engine is also not running, that rules out the transaxle and the rest of the drive train, right up to the power plants (ICE, MG1, MG2). It would also rule out belts, and the A/C compressor, as they would only be moving when the ICE is running (classic A/C compressor is traditional mechanical powered by ICE).

Perhaps a bad bearing on one of the electric coolant pumps? I might guess the inverter coolant pump. Not sure if the classic has an electric pump for the engine coolant for cabin heat. The THSII does.
 

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I, too, have a squeak that occurs on my 2001 most mornings when started from cold, and pretty often when going up a particular hill from a stoplight to ~50mph.

My previous description of it and from others experiences, eventually it'll lead to a check enigne light (mine has once or twice). Unfortunately, the check engine light will clear itself after a few restarts, so I've never been able to prove it to a dealer, but I have pulled the codes on it and it was: P1436.

See:
http://autos.groups.yahoo.com/group/toy ... 015-02.pdf
US TSB EG015-02
Aug. 2, 2003, M.I.L. "ON" P1436-HCAC Bypass Valve Improvement, 2001-2002 Prius. (road salt may cause issues with valve. possible fix is to replace the Front Exhaust Pipe Assembly if any shaft binding is evident.)

If you hear of reports of changing the exhaust system or the catalytic converter, it's usually thanks to this squeaky-stuck valve.
 
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