2021 Prime Cold Start Rattle - Gen3 Prius Bad!

I don't drink coffee at the gas station, so the color sensation of used oil is not clear.))
Engine knocking can occur due to improper operation of the fuel system, spark plugs, ignition coils, improper air supply settings, a dirty filter, and even a forgotten sock in the air tube.
For fortune telling on coffee grounds, we need more objective parameters. Is it possible to remove error codes from a hybrid?

 

I think you need five posts to post a link

 

I haven't had that issue but I'm only at 45K. I do 10K mile oil changes and it barely gets light brown. Heck, I have to use a tissue to figure out where the oil level is for the next 3 months after a change.
What kind of oil are you using and have you been losing any coolant? How much oil burn are you experiencing on your 5K mile oil changes. How does the spark plugs look? Can you get a bore scope down in there for a look? In your hot climate, I'd probably move to 5w20 or 5w30.
Quality oil makes a difference. I inherited my dad's SR5 pickup w/low oil pressure, when hot and idling. Change the oil and the problem went away. Later found out that he did his oil changes at Jiffy Lube, so whatever oil they were putting in couldn't withstand the operations of that v6 engine. Never had a problem with low oil pressure again.
If everything else checks out, It could be a bad timing chain tensioner. An experienced Techstream jockey should be able to see that in the diagnostics screen.

 

Good to learn 0w-20 doesn’t help. What oil filter was used? I have heard it on a new 20 Prime I had, and another 20 Prime I have now. It happens after a long period of not using the engine.

 

How’s the engine coolant level in reservoir?

 

You have a hybrid not a plug in? When you change oil and filter you hear nothing on first start? My first Prime had start up noise when less than 1000 on the clock, if I drove in ev a long time. Sounds like main bearing knock, but a drained down chain tensioner is another possibility.

 

Op has a Prime too! If it was a main bearing knock - issue wouldn't go away after a minute into startup. The ECU is correcting something to get rid of the knock. Again, a very experienced Techstream jockey should be able to figure it out by looking at the raw sensor data.

FWIW; my engine starts almost everyday - I'm just beyond my 25 mile EV limit on my commute. I usually force a start when I get up to cursing speed on the highway and switch back to EV on surface streets.
When I change my oil; I don't bother to do the "chicken-dance"; Just turn on my defroster to force an engine start. If you can't outsmart the ECU, Skynet will get ya.....

 

i wonder if it could be an unburned hydrocarbon problem like gen 2 and 3

 

I think it is the same dry start as when doing an oil change. Sounds the same to me. There isn’t much pre filling the filter when it is horizontal. I try to fill it a little bit. I think it is bearings, rod or main, or chain tensioner draining down. My neighbor has a 2021 Forester and I hear it every tine he starts it cold, even not that cold. Those have a filter base pointing down in the engine compartment.

 

i'd like to hear a recording

 

If that's the issue, moving to 5w20 should quiet it down a bit. I would also look at the oil filter, does it have an anti-drain-back valve?

I don't get a rattle when I do my oil changes but the first thing I do is fill the new filter with oil. Then I jack up the car and drain it. The filter is usually less than half full by the time I get around to installing it. Put it in the horizontal position to see if oil will come out. If nothing comes out, I top it off a bit. It weeps a bit while I tighten it down. Put in my 4 quarts and fire her up. No rattles or knocks, but oil lamp stays on a few more seconds longer than normal. I'm still on 0w20, but will move to 5w20 if I start burning more than a couple of cups of oil between oil changes. That's what I did with my old Prius C, before an uninsured motorist totaled it out @ 98K miles

 

The previous versions of this model engine, with a cartridge element oil filter, had no anti drain back valve. The oil should stay full in the filter the way the filter casting is mounted to the engine. I am using a Fram Ultra now, next will try a Purolator Boss, already have it. Sound is still there. Lately the engine has been starting after longer non use in traffic situations, and the rattle is hard or impossible to hear. It’s there though, and it’s real.
Another possibility is the thin oil slowly draining back through the oil pump gears, which corresponds to long periods of non use.
Anyway it is what it is and using the engine more often helps.
I have never had a car I don’t think that didn’t have rattle after an oil change unless the engine was so noisy from the fan or other things that it masked it. There is time before the oil pumps up through the empty lines, it is as simple as that.

 

From what I remember, the cold start rattle occurs after a previous start and shutdown that doesn't bring the engine up to full operating temperature. There may have been other causes. In all my starts of three Prius vehicles I have never experienced it

 

When you switch to EV on the highway, the engine will need to warm up before being "added" to the propulsion system. With Hybrid Assistant running, you can see that by the RPM staying at 1200 rpm and the engine power output being almost zero. So during that time, your HV battery is being drained more rapidly (highway speed). I switch to hybrid a few minutes prior to get on the highway. I'm still in EV during that time. No point in wasting electrons while driving at highway speed.

 

Your correct: I just prefer the EV's merge capabilities over that of the hybrid. I don't mind 'wasting a few electrons', but if/when I need my ICE - it needs to be there (ready); not warming-up and not contributing to the overall power-train. High reving a cold motor is a very good way of needing an early replacement....Just saying, a thimble full of gas every month is a lot easier to swallow than an engine replacement. There are ways to mitigate costly repairs - good procedures and habits is one way.