At 80,000 miles I had my local Toyota dealer change the transaxle fluid in my 2004 Prius. The receipt showed they put in 3 quarts of ATF WS, and charged me for that much oil. I noticed this upon bringing the car home, and took it back asking them to check that the proper amount had been put in, as the Owners Manual said drain and fill with 3.8 US quarts. They said they checked and it was OK. At 100,000 miles, I began hearing an occasional hum in the transaxle, so decided to change the oil myself. I drained out about 3 quarts, the amount the Toyota receipt said had been put in. I noticed some very black substance and some fine metal shavings on the drain plug, which I cleaned off before replacing. When replacing the oil, I put in 3.8 quarts, and just a little flowed out the fill plug located on the front/side of the transaxle. I then put the plug back in. It seems to me that Toyota put in about 3 quarts because that is what drained out, and I am wondering if that amount is what dealers typically put in. Also, I wonder if low oil might have caused the hum and metal shavings. Or am I just unlucky.
The black residue on the drain plug magnet is normal, usually there is a little mound on the tip. Very fine metal shavings are also normal. It is not normal for 3 quarts to be added. That was a mistake on the dealer's part. (It's sad to consider how much you were probably charged for that poor work. Glad that you can DIY better and cheaper.) I'm also interested to know whether the hum is still present. It is likely that was provoked by the low transaxle fluid level causing excess gear wear.
I haven't driven it since changing the oil yesterday. I plan on driving today and will report on the hum.
Craig Your post is of concern--Oil level or lack of it can seriously affect longevity. I have seen several units having been run moderately low on oil that have suffered lube failure on the radial ball bearing supporting MG1 next to the resolver unit. (the resolver allows the ECM to "see" what both 3 phase units MG1 & MG2 are doing. Motor "Hum" can be caused by a mechanical fault--like a bearing failed on a rotor (reference to the radial ball bearing) or an electrical imbalance in the windings. If the car was in my shop I would be inclined to attack it with a Techstream to see if there are any soft sub codes lurking about. Next I would be disconnecting the 3 phase motor(s) connectors (after powering down the current in the car) and then testing the motors with my Meggar or Fluke insulation testers) NOTE THIS ACTIVITY IS FOR THE TRAINED TECH--HIGH VOLTAGE IS INVOLVED. I would be inclined to approach the dealer/repair shop where the apparent oil level issue occured and explain your findings and current symptoms then see what resolution you get. Very best of luck Actros
Today I drove about 70 miles, and everything sounded normal. I am hoping that all will be ok. I am glad this is an old car without too much value.