Noisy engine at idle

I have a 2007 Prius that I bought with 125K miles and it now has 190K. It has been a great car overall, but recently I am concerned about engine noise. I will come clean about my shortcomings on maintenance and any blunders in an effort to narrow down what might be happening.

I replaced my tires, that had some uneven wear, and now the prius drives whisper quiet. Its a good time to start listening at all the other noises.

The motor sounds louder than normal around the valve cover area. Not a typical valve tapping... maybe a chain? Its a rattle. Not exhaust noise. Doesn't get any worse during acceleration, most noticeable at idle when not many other noises. With the hood closed it can almost be ignored... but with the hood open, staring at the motor, it has me worried.

About 6-8 months ago, I noticed my oil was low... really low. So low that when I drained it I put it back in the quart bottles to see how much was drained. 1.5 qts. There was no indication on the dash of any issues. Replaced the oil and has not been losing since.

Recently I took a 600 mile trip and when I was about to return, I checked the oil. I couldn't get a good read on the dipstick and was convinced that I was low again, so I added a quart. Measured the next morning after I got home and I was overfilled. I immediately siphoned out oil to put me at the full level.

Believe it or not I am otherwise pretty handy.

Any thoughts as to what might be going on? I don't mind a little rattle and hum, and the prius drives perfectly. I am more worried about the car dying on the highway or worse a bridge or tunnel.

 

Hi Patrick. I think the noise is something more than valve train. I have had other "noisy" Toyotas that were primarily valve noises, this is different. This noise also doesn't go away after the engine is warmed.

 

if it were a loose timing chain, the noise would probably be it banging against guides? Any thoughts on repair or living with what might be a loose chain?

With the high mileage it has, and the overall worn appearance of the car, I would probably just live with some noise if I didn't have a high probability of getting stranded.

I also had previous plans to replace this car, but I still would like to know whats going on in the event that I pass it on to someone else.

 

I tried to use a mechanics stethoscope but it didn't tell me much.. I put the end on the valve cover and by the water pump and it sounded the same to me, noisy but maybe not the same as the noise I hear without the scope. I really don't use these much, so might just be I suck at diagnosing noises. Maybe I will put it up on ramps and listen from underneath.

 

I probably will not tear apart this motor. Really more concerned about a sudden failure and being stranded. My concern is when does a noise become a serious concern when you are not actively burning oil, notice any issues with drivability or increased noise on acceleration. I think Toyota tends to be bullet proof and I am already driving a "clunker". Just looking for help determining has a good chance of being a red flag with these cars.

 

I can't say it sounds like the video from oldtechaa. The noise isn't very noticeable from inside. It definitely does not appear only when accelerating. I think it is noisy overall and doesn't sound like it gets worse under load.

I will try and post the noise. Any suggestions on how to post that? Youtube link?

I did see a post on youtube about a water pump noise. Sounds like that... and my pump is original.

Thanks for the suggestion on maintenance mode. Wrote those steps on an index card and will put in owner's manual for future reference.

I will try to do some more info gathering tonight. Really appreciate everyone sticking with me on this.

By the way, if the valve cover is removed, can the gasket be reused?

 

Anyone know if it is OK to idle without the accessory drive belt on?

I did this with my Ford Ranger to rule out noise issues. I want to remove the water pump to see if it is producing the racket, but I just don't know if there are any sensors that would have a panic attack.

 

I took the belt off and the rattle noise was gone. The water pump pulley had a little play in it. Ordered a new water pump ( and plugs and pcv valve... time to catch up on maintenance!!). That video was pretty accurate and pulling the belt was a great quick check.

Thanks to all for the great ideas. I learned a lot and have a few more tools going forward.