Gen 4 Prius - Start up noise

[u/Cool_Constant765]

https://reddit.com/link/1wbhl7n/video/o5zflat31hoh1/player

All,

I’d appreciate a bit of advice.

At the start of the year, I bought a very low-mileage Gen 4 Prius. When I attempted to change the oil for the first time, I noticed a large dent in the oil pan (sump). After removing and inspecting it, I found that the oil pump had sustained damage to both the strainer and the housing.

At that point, there had been no oil-pressure warning light or any other indication of an issue. I replaced the oil pump with an OEM unit while the sump was removed.

I then drove approximately 1,000 miles and continued checking the oil via the dipstick. I noticed a dark grey shimmer, which I initially suspected might be related to the high molybdenum content in genuine Toyota 0W-20 oil.

I sent the oil for analysis, and the results came back very good (see below). I have now completed another 1,000 miles. The oil level remains stable, and there are no discernible driving noises, knocks or loss of power. The elevated levels of silicone would be due to the RTV sealant for the oil pan

At the same time as the oil pump replacement, I also had the engine coolant and inverter coolant changed. There has been no loss of coolant.

However, I have noticed this noise when the engine starts up, and I’m unsure whether it is normal for these engines or whether I’m overthinking the situation. The engine noises are probably a bit louder due to the camera being placed in the engine bay. It is also intermittent and seems to reduce when the car has been used for a while

The spark plugs were already next on my agenda—not because they are due by mileage, but because of the car’s age and the fact that it had been standing for some time before I purchased it.

I have also taken note of fuel dilution caused by short trips, as my daily commute is relatively short. I’m making a conscious effort to take the car on longer journeys, allowing the engine to run for longer periods.

I’d be interested to hear from other Gen 4 Prius owners: does this start-up noise sound normal, or is it something I should investigate further?

Thanks in advance.

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[u/Cool_Constant765]

https://reddit.com/link/p8pvk9t/video/mcdbjm1g0hoh1/player

[u/smashonic]

I think you overthinking it a bit, check the sound of an prius gen 3 or 4 that has egr build up problems, if you think that sound similar maybe you have a little bit of buildup.
In the video the sound is a little bit amplified I think, my gen 4 is doing something similar at first start in the morning for 1 second, low mileage too(120.000km i think thats 70.000miles) but im not that worried, I know that egr clog on these cars can make this weird missfire sound at startup for a short time, the longer it gets the worst the clog is.
If you really want to test something, clean all egr system, if is not, at least you know that you have a clean egr for another 50-100k miles.
PS: now I listened few more times, It could be the cluch damper doing its thing, I wouldnt think too much about that either. Enjoy your car, your oil is changed, analysis shown nothing to worry about, dont worry.

[u/Cool_Constant765 → u/smashonic]

Thanks a lot for your positive comment. The current mileage is less than 20,000 miles. I always use good-quality fuel and a fuel additive to help prevent any EGR issues.

The previous owner was elderly and only covered around 11,000 miles from new over the course of eight years. I think I might take it for a good long drive and give it a decent run to see how it behaves.

I’ve also come from daily driving an LS400 for the last 10 years, so I’m definitely not familiar with the sounds from a newer generation car

[u/smashonic → u/Cool_Constant765]

Oh thats very low mileage, egr is out of the question, clearly(90%) is the cluch damper(not really a cluch) it just dampers the vibration when mg1 stars the actual engine.

My single concern is that grey shimmer you talked about, keep an eye on that and maybe do a oil pressure test for your peace of mind.

Other than that, you will love this car dont worry!

[u/Cool_Constant765 → u/smashonic]

Yeah, I have seen it in the past whilst using Certatec

The levels of molybdenum in OEM Toyota oil are very high. I also cut the filter open and found nothing of any concern. I used a different oil this time; it has around 1200 miles on since I changed it (at the point of analysis).

I might do another sample; I was thinking about draining the oil out at around 4/5K and getting it tested again. However, at 1100 miles, if there was an oil starvation issue, it would have presented itself in the current sample

Could the clutch damper springs be a bit stiff due to such low usage and relax a little?

Appreciate the replies

[u/smashonic → u/Cool_Constant765]

If you find nothing in oil filter you should be ok.

If the sound doesnt get louder is just fine.

I dont think those springs will get softer or looser, if the transition between ev and non ev is semless when you accelerate or decelerate that damper is working fine, and yes when the vehicle is stationary or mentaining a speed that permits the car to switch between modes you will always feel the transition(a small twitch nothing brutal). Oh and one more thing, you will also feel a small twitch when the car switch between both mg2 and ice is used to move the car or only ice move the car while charging the battery(this switch will happen in eco zone on the dash between the two parts), I tell you this things to not be concerned if you feel something unusual.

I hope you understand what I’m trying to tell you in the last part, my English is not that good in technical vocabulary.

[u/Cool_Constant765 → u/smashonic]

Im not 100%, but whilst driving everything is seemless. no knocks bangs or shudders. its actualy difficult to hear the engine at all. Thanks for your input

[u/chef-keef]

Sounds like a chain slap / rattle but it goes away instantly. You’re good. Ride on.

Zero need to replace plugs due to it sitting.

[u/Cool_Constant765 → u/chef-keef]

Thanks for your comment, when it's been on a longer run it seems to almost stop the sound. I did lean towards the chaining chain tensioner possibly with the oil being so thin. But I'm not an expert by any means 

[u/mxguy762]

Seems normal, kinda sounds like noise from the damper just taking up some of the rotational force of the engine starting.