What kind of engine work should I do?

So as some folks might know I just obtained a 2010 Prius with 237k miles on the clock (quite cheap lol!) which was not running and I diagnosed it with a failed clutch damper. I'm in the process of pulling the engine out but since I don't have a crane on my hand I'm attempting a cheap man's route (basically removing all parts down to the short block and lift it out with 1-2 helpers). I removed all outside parts, valve cover and timing chain yesterday as well as all the head bolts. I'm going to lift off the head and try to remove the block in the next 1-2 days.

My question is how much work should I invest into the engine? Should I do a complete rebuild with updated pistons and rings, or just a head work is going to be good? As of now what I can tell is that the oil in the crankcase I drained out is a little milky at its due service time, indicating a slightly leaking head gasket. The timing chain is pretty tight at the time I opened the valve cover. The car was low on coolant when I got it, with P0300/P0302/P0303 stored as permanent DTCs (those echo the head gasket problem).

I guess I'm likely going to find a local machine shop to do the work regardless so want to hear folks opinion about it. It's a 4th car in our family so I'm not into the idea of making it like new, but definitely don't want it to break in a short time after I invest so much time and money into the engine work.

 

Darn...I just separated the engine and transmission and found the transmission input shaft is shot...

Wondering if replacing this shaft is easy? I know Toyota does not like us to service the transaxle so there's probably not too much information I can find out there, but it looks like the input shaft is available as a part that can be sourced from dealer or bought used off ebay. Is it as simple as removing the plate in the photo and put it in, or I have to completely disassemble the transmission?

 

Noted. I just removed the head and separated the engine from transmission last night (broke 2 bolts that hold the engine to the trans...) and found the transmission input shaft snapped (see my last reply). I'm not sure if the clutch damper is OK -- that I have to take a look after I lift the short block out of the car (need a helper). By looking at the top of the pistons, I found that the cyl 3 and 4 pistons are exceptionally clean and definitely have traces of coolant on top. Cyl 2 piston has the heaviest carbon deposit while cyl 1 piston looks somewhere in between.

I'm struggling a little as of how to proceed. It looks like replacing the input shaft of the transmission is not too difficult -- only need to drain the oil and remove the input shaft cover. I can even do this without removing the trans. However when I try to source the parts it does not seem like something easy to find and dealer charges $400+ for the input shaft, while a used tranny can be bought for $200-300.

 

OK.. then I guess a used transmission would probably be my best option. Thanks a lot for the really helpful input!

 

Yeah I read that. I'm cleaning all parts before assembly for sure. Honestly the amount of EGR gunk on this model seems to be much smaller than the OM642 I have worked on before lol! Not a big deal to me.

 

I just got a used transmission today from a local junkyard for $250+tax. This one has 64k miles on it. JDM engine has one for $99 but shipping is $250 to me. I'm around Philadelphia, not too close to north Jersey.

I sort of agree with you on the engine. Upon initial inspection the pistons are in pretty good shape. Connecting rods are not bent at all. I guess I'm probably not going to disassemble the short block but still I'll do some measurement on the cylinder diameters to make sure it's still within spec. Then I'll just do a resurface of both head and block and install new gaskets and timing chain. If it burns oil I'll just keep adding oil that's not a big deal to me.

 

I would love to but a used engine costs $1500-2000 based on my search, and I might still run into the HG issue...

 

I'm willing to solve this issue honestly and am seeking possibilities. I called local engine shops and none of them do rebuild on this thing so I guess my choices are either find a used gen4 engine to put in, or replace the piston and rings by myself. I have never done any internal engine work before other than replacing head gaskets, but I'm willing to try...

 

The cylinder walls look pretty good with no visible scratch. I don't have a bore gauge on my hand, but I guess I can use my calipers to do a rough measurement see if the bore size is still within spec. I'll post results.

 

I see that post but that's back in 2019... You know how crazy the used car market has been in the past year. See those used engines cost $1500-2000, plus with 60-80k miles on those engines I would expect the HG problem to develop soon. My current plan is to do some measurements on my current engine (namingly the conditions of the cylinders). If they are still in spec I might just go with replacing the pistons and rings (this does not seem too complicated according to the TSB), and then put a new gasket set and timing chain. Otherwise if the cylinders are not good I'll need to go for a used engine regardless.