Any Ideas What The Noise Is In My 2013 Prius With ~283K Miles?

Scroll down to the last paragraph for the video of the unknown sound and observation of me probably not having to add coolant when I saw was down.

If you feel like reading, here we go with what's on my mind.

Since the issue I noted before after running two bottles of Techron in two tankfuls of gas accordingly and having the engine oil overfill situation on a ~3hr each way road trip with later finding the PCV Valve was stuck open I guess causing the two death rattle experiences with misfire situation check engine light codes when I was on an incline starting the engine, looked like I better prepare for the head gasket failing. Thankfully, no death rattle since or misfires.

Well, since then I've been noticing some bubbling sound in front of me usually when the engine starts. Then and only then. Though my coolant tank hadn't been going down and my oil looks good. Actually looks like the engine is consuming less oil as well.

For the last two years however; during the summer with hot 80 degree F days or more, the HV battery is down to maybe two bars or so, driving at a low speed or accelerating from a stop and accelerating slowly while in ECO mode since that's what I drive always and my AC on the highest fan level... I get a rattle where then I let off the throttle and accelerate again slower usually or really fast without issue unless when accelerating slowly I throttle at some to fast rate where then might rattle again. I've also had all three 1/2" foam pipe pieces fully blocking the engine radiator grill and nothing blocking the inverter radiator grill.

Wondering about that acceleration rattle with the AC full blast and thinking temperature might be a causation, I've recently began monitoring the temp more with Hybrid Assistant and Car Scanner since I was suspecting the engine coolant temp was going higher and maybe my fan wasn't working or something else possibly like the radiator needed cleaning or I needed to remove at least one of the foam strip sections blocking the grill or maybe more or the head gasket was leaking due to temperature changes caused by undesirable differentials between the block, gasket and head.

After monitoring, I confirmed the temperature was going above the typical 194 or less and up above 200 and up to 205 during the rattle sound noted during accelerating from stop or low speed was happening during the low HV battery situation and the AC on high fan. This last time was maybe for about a half hour of freeway stop and go traffic where the low speed acceleration rattle was happening a few times where the outside temp was almost 90. So I removed one foam strip after observing at the next stop and haven't seen the temperature rise about 198. Haven't heard the rattle since as well.

Well, yesterday morning I took this video (linked below) after I got back from doing some chores since I noticed the coolant level was down before heading out. No death rattle with vibration issues during startup since the original first noted misfire code check engine light issues and at first post cleaning during the initial startup where I guess was due to me not disconnecting the 12V battery maybe or possibly the cooler nights and humid rainy days during that time and some moisture condensing since went away in a second or two.

After driving you can see what the level returned to which is above the full line where I left. What's up with that?

When checking the coolant when I got out of the car after returning home as shown in the video, I also heard the noises I've never heard before. Those noises really threw me off as I don't recall hearing before, though really never listened for since wasn't really monitoring like I have been recently the last year. Really this is the first time I've gotten out of the car and opened the hood to listen for anything.

Any thoughts, questions, comments and/or suggestions?

 

What temp is considered overheating? I didn't get any warning lights or codes thrown.

Seems all good now with all foam pieces removed. I'm still afraid I may have caused some damage, though hopefully paranoid and now will be more diligent.

Dedicated HUD's as I noted elsewhere in each car to be safe using smartphones with Hybrid Assistant and Car Scanner and the Panlong bluetooth OBD2 adapter that I'll now always use when driving from now on. I do have a OBDLink if needed and that dedicated eBay amazing little old XP laptop tool.

Yep, toting Mom around this season and she likes the AC always when warm out. As noted by last Thursday I was still at two pieces of foam and one removed. After that post was written I removed the other two so no more grill block until maybe temps dip below 55°F.

Not noticing anymore. Not throwing away since will use for winter, though I'm totally understanding like after over 55 degrees F out... remove.

My thought is the EGR restriction causing a knock since studying more seems to not be a low HV battery or higher temperature situation. Is a downhill low load low acceleration or even flat level surface low load low acceleration issue I believe from reading more into understanding how the EGR circuit works. I think I need to thoroughly clean or replace my EGR Valve maybe? No issues if I accelerate faster so creating like a higher load situation where the intake is the source and not a restricted EGR circuit seems where I wonder what the exhaust manifold looks like since didn't even bother to look into.

Wondering if also if that EGR circuit when has the spouts of restriction, during those low load events since isn't always reproducible, might vaporize some oil due to the vacuum?

Is pining the same as knocking?

Post Techron treatment with engine overfill situation, my oil level consumption has really slowed down. I need to check my numbers, though not a concern and the oil looks good still. Other than is time for an oil change.

No starting sounds with the engine. No death rattle or vibration since I did the above Intake, PCV and EGR Circuit cleaning post Techron and oil overfill situation causing the misfire codes that haven't since presented themselves. Totally paranoid will, though haven't heard and amazed still getting 50-58MPG's when not going over 66MPH on the freeway even. Rainy day today as well. I did get like a little worse MPG when I had my Mom out and doing the no way any grill block, full AC blasting days of laundry, Goodwill donations and shopping. Temps stayed at or below 195°F.

Surprised actually when I was leaving going downhill is when I noticed the 188 engine temp, almost charged HV battery and then low load, low acceleration knock I believe is what is now after reading more and better comprehending the EGR circuit performance. That went away with just letting off the gas and being a little more aggressive on the throttle so intake only I assume. Makes me think I need to assess the EGR circuit again some more and try to get into the exhaust pipe too since was so sludgy back when I did clean and didn't.

No way would I ever use sealer. Never ever ever. Toyota or Toyota OEM or Mobile 1 full synthetic... maybe Fel-Pro and whatever Toyota Service department use like 3M Silicone Dielectric Paste or Sil-Glyde or 3M AntiSeize. Yikes!!! No, no way coolant crap like that man. What are you thinking.

Full gasket kit and head rebuilt is the plan in the near future. Hopefully not bearings, rods, pistons and rings rebuild. If so, might be time to swap in another engine (Gen 4) and do the existing engine rebuild myself outside of sending to the shop if any work is required like with the head which is roughly offhand, thanks to everyone's positive reminders and re-enforcement, possibly valves, valve seats, machining and at the least inspecting, lapping valves and testing seals. Probably missing some steps. I do have a surface plate and machinist straight edge and feeler gauges with other machinists tools, so can test to the Toyota specification.

The only tool I need is that twelve point head bolt socket. Plus I really need to calibrated my torque wrench before doing.

Otherwise, is time for the inevitable head gasket head job with timing chain and tensioner new maybe. Possibly new water pump and thermostat while at it.

I do now have a ~240K 2006 for backup and a new learning experience. I'm still amazed how I've done not much at ~284K with the 2013. Simply amazing and some of the best in the World engineering and support groups, many thanks and much appreciated.

Yes, I have an Prius addiction and my name is James. Currently struggling with head gasket repair denial and a coping mechanism where I'm sure I can make it to 300K before doing.

 

Thank you! My Mom even was commenting how better the AC was after I removed all the grill block after making the above post. Totally noticeable in performance. I literally have a genetic condition anhydrotic ectodermal dysplasia and don't sweat at all, so definitely sensitive to temp. She's a carrier and still sweats though loves the cold air even if gets me colder than I prefer.

Anyways, great data!

I'm thinking the grill block won't go back on until the temp gets below the what I've observed to be 55°F limit. Where I've had this empirical with quantitative ad menti concepti observation that if the temperature is 55°F or less outside, I drive 55 miles per hour or more, then I'll no way ever see 55 miles per gallon. I suppose that was written pessimistically compared to my typical optimistic detail of.