Hello everyone, been lurking here for a while, and now I am at a point where I need some help, and advice if anyone would care to assist. Long story short my 12 CT developed the dreaded knocking and shuddering last month on a consistent basis. Had it towed to my local independent shop thinking the worst as my 12 Prius had the same issue a few years back, and that ended up having a "new" motor installed. They went thru the CT, and came back saying that at my last oil change a week or so prior, the shop (not them) overfilled my oil, and that got into the intake, fouled a plug (cylinder 1). Anyways they drained and refilled the oil, cleaned the intake, changed the plugs, and sent me along the way. Fast forward since the initial visit (been back a couple of times since then for the knocking on start up and coming off the electric and switching to the ICE. They finally came back saying it was my head gasket. So I am now batting 2 for 2 for having the head gasket go bad.
So in regards to the problem. While it's a definite long shot, no real chance that the overfilled oil would/could contribute to the demise of the head gasket? Since the overfill and the initial diagnosis, I probably only traveled a couple hundred miles, my longest trip being like 120 miles due to Covid. Prior to that, maybe once in a blue moon would I get the shudder on startup especially in the colder/ damper months in which I always thought was the cold soak that I've read about, so didn't think much of it.
Secondly JDM engines, I cannot justify spending nearly $2k on a salvage engine with 93k already on it, or $1700 with 130k plus from say LKQ, where as I can get a "low" mileage JDM shipped for $1200 or so.
Does anyone have any experience with them? I've read the threads on PC and asked a question but no response as of yet over there. Gut feeling is to just do the swap, and not a replace and rebuild as the original engine has 178k on the clock.
Thanks in advance!

 

How bad is the knock? I actually just purchased a very high mileage ct with 191k that runs great, and I'm anticipating that eventually I'd have to replace. I'm not sure an overfill would cause headgasket failure directly.
Lkq prices are fair if you search on ebay for a long block. Also look into the 4th gen Prius conversion for lower mileage, which is eventual plan when the time comes. My experience is mainly in the Jz engine world but the 2zrfxe looks like a simple platform.

 

Our engine came
from LKQ, so I cant speak to the other company.

as for the knock, the intake is just one of the cleaning items. The entire EGR system needs to be cleaned (or replaced). So people get a replacement so they can just swap a clean one in to keep driving. They then clean the old one as time allows. Hopefully that fixes it for you, but it’s possible the HG has already had warping

as far as over filling, how far past the high dot did it get filled. You can get to the bend without much issue, but more that that you risk frothing. The mixed in air then can effect its ability to lubricate properly. It doesn’t take much to drain some out. If you unscrew the oil filter housing cap, it’s the easiest to drain some and tighten back up.

 

The shop that did the work didn't tell me how much of an overfill there was. I can ask and see if they remember. On its multiple trips back to them, I discussed the EGR system, as a possible issue as well, but after they went back to check it, is when they came back and said the HG for sure.
If it could definitely be attributed to the overfill, I'd approach the shop that did the overfill and a go after them, as it's already been documented, and they accepted responsibility for their mistake, but its probably to much of a coincidence that this occurred.
Regardless though if I end up going the "new" motor route, I will get the EGR system and manifold from old engine (if replacement has them already) and keep them to clean out/up and have a spare to swap between my Prius and CT on probably a yearly basis.

The knock seems to vary in intensity. Sometimes it seems to only be a second or two with out much in the way of shudder or "volume" of the knock, other times it seems likes its an eternity, and the shudder is very prevalent, and the "volume" is very audible.
I've read a bit about the gen 4 swap, and I can discuss with the mechanic what he thinks, and cost involved vs a more or less plug and play swap. Being unemployed because of the pandemic does not help in wanting to get into a slightly more involved process, but if a low mileage gen 4 engine could be found for a decent price, and the shop didn't think it would cost to much more then I would possibly entertain that swap.

Thank you both for replying, appreciate it.