knock/tick/click sound under load and acceleration

186k miles is a lot of miles. A car can develop all kinds of strange noises when they are that worn.

you might want to try running a few tanks with techron fuel treatment. maybe that'll help it. But really not much you can do on a worn engine.

 

It may be a valve lifter out of spec. Someone skilled with a mechanic's stethoscope may be able to verify that. The Prius maintenance guide says to get valve clearance checked regularly, but it's a real pain on that engine, requiring a partial tear-down. I'm not in the industry, just a hobbyist and forum enthusiast, but I've never heard of anyone actually doing it. The general consensus seems to be it's a well-made engine and, given the low cost and high availability of salvaged engines, it's not worth the work especially on an older engine. If a valve burns, the car will let you know but it won't strand you.

 

My gen 2 had a minor exhaust tick that would get quiter after a few miles. I was happy living with it. The guy I sold it to fixed it by replacing a donut seal between two parts of the exhaust.

 

Given the symptoms, it sounds more like the exhaust. Valve noise should be noticeable on cold start. Exhaust noise will vary with manifold temp. Some can tell by the speed and location of the tick. Noise from a single lifter will be at 1/2 engine rpm, coming from the top of the engine. An exhaust noise will be at 4X engine rpm, coming from the bottom rear of the engine.

 

How long has it been since you changed your plugs? any idea what the coolant temp is when it's pinging? My last car was a Ford and it pinged when it was hot outside and temp was hot. I was too cheap to buy 92 octane gas so I would add 1 gal of e85 to a 20gal tank and the pinging would go away. Not sure if the Prius does but a lot of new cars have anti knock sensors which adjust the timing if the engine starts pinging.

 

Yeah that's the sound of an engine with 186,000 miles. Lifter noise. Probably lived on dealer vat oil all its life. Look at its history. Go to toyota.com/owners and join and enter the car's vin.

It will show you every visit the car has seen to an authorized Toyota dealer. Probably show you why it was traded in. See if its had its oil changed at the dealer regularly.
If it really bothers you take the valve cover off and see how bad it is. My bet is its bad.

Based on being on this site more than 10 years the engine in general and the top engine in particular are very robust. The engine uses solid lifters unlike most cars that use hydraulic lifters. Lifter wear is serviced by replacing shims under the sold lifters. Very few posts about the top end most are about how clakity clakity the motor is in general because of the nature of this valve train but under load and during acceleration the valve system is very quiet. I can't recall one person who has replaced those shims and post about it. Probably labor intensive and given your miles a salvage motor is probably money better spent.

The somewhat unique part of the VVT system is its serviced by its own little oil filter for the VVT system. Its a little screen filter.
In your case being curious how it was treated in its earlier life you may want to pull that filter and clean it and look at it.
Its behind a torx bolt right under intake manifold runner cylinder #1.

 

Note that the different sounds of the engine is likely partially due to the engine going through the different warm up stages. See this thread:
Prius Stages of Operation & Operating Mode Availability -A Reference Aid | PriusChat

Open the first pdf on that page and then take note of the "Ignition Timing" row. My engine has a noticeable ticking noise in S1 (similar to many many other cars - doesn't sound like anything I'd worry about), then in quiets significantly in S2, quiets further in S3, and then is unnoticeable in S4. I believe the timing is advanced the most in S4, which is why this occurs for me. Also seems to be related to the engine temperature. If I start the car with a warm engine, the ticking is quieter, even in S1.

The Prius engine is very good at reporting when it has problems with codes. I agree with others - for an engine with 186k, I wouldn't worry about it. You could try a few tanks of cleaner in your gas and see if it makes a difference. Only other thing I can think of besides taking apart some parts of the engine like others have mentioned is going up to a thicker oil, which might reduce the ticking noise. You could try a 10W-40 oil if you're really worried about it (with the expense of slightly reduced fuel economy - 1-2%ish, and slightly harder cold starts).

Also important to note is that there is a big difference between a "tick" and a "knock". If you have engine knocking (a form of engine misfiring), the engine will run very rough, and you'll notice strong unusual vibrations from the engine.

 

If you have a lifter seriously out of adjustment, you could burn a valve. That will light up the CEL and you'll loose power, but it won't blow up or leave you stranded.

 

Like JC said....thats alot of miles.

The horrible truth is at that many miles I would worry alot more about the hybrid battery going t.u. That will bust you out.

 

nicnacpatawac,
This is the best video of the noise I've found. Have you discovered anything on the source of this? My 09 has sounded like this almost since new. Obviously it was less early in life and most noticeable to me in winter on cold starts mostly. Now fast forward to almost 200,000 and it has gotten a bit louder with the miles and wear. I figure if it was something significant it would have let loose long ago. At the 60k maintenance it says to inspect valve clearance, but my dealer said back then "we don't adjust prius valves or check" and sound normal. It seems to me to be a valve clearance issue or the VVT sprocket? Anything else like a rod bearing or piston pin would have parted ways years ago.

If there has been any changes in your search for an answer let me know. On thing seems to be true, my cold engine taps more and lessens as it gets to operating temp. The hotter the summer the less I hear it on startup although it is always present. Sort of sounds like a sewing machine.

 

I think I hear it is it after you let off the gas? Thats kind of trailing clicky click. Thats weird have not heard that before. What kind of oil are you using and are you keeping it at the full line.

has the car ever ran so low on oil it turned on a check engine light?

 

Under load or acceleration? Sounds to be Spark Knock/Pinging.

Posted via the PriusChat mobile app.

 

I know this thread has been quiet for a while, but I am dying to know if anyone has resolved or at least identified this noise.

My '08 is making the exact same sound. It has 96k miles.

- I don't believe it is detonation pinging, The sound is to consistent and lacks that almost diesely clatter you'd expect.
- It could be a lifter or an exhaust leak, but if I raise the RPM's while in neutral, I don't hear anything. So I feel like that eliminates those.

Are there any other systems that would match the engines RPM's while in gear? Like a speedometer cable or something like that? (It probably doesn't have a speedometer cable, just trying to think of overlooked components....)

 

You mean raise RPM in PARK? Pushing throttle pedal when in neutral does nothing. And pressing throttle in park just raises the RPM but doesn’t really load the engine at all. So there’s nothing to proof that it’s not exhaust leak or something like that.

 

Yes, in PARK. My bad. Thanks, Valde3.

I know in the past (with other vehicles) I have been able to replicate minor lifter taps and exhaust leaks while in park. I guess that may not always be the case.

I'm still wondering if there might be any other components that could cause a noise during acceleration. From what I have read, the issue has occurred in low mileage vehicles as well.