Its time for a rebuild.

Well, it finally happened. The old girl quit on me, at least the engine did, I knew this day was coming, just wasnt sure when, the motor had been limping for the past couple of years.

Its a 2010 Prius 5 with 290k on original motor that has been burning a quart of oil every 1500 miles for two years now. A couple of weeks ago the death rattle popped up, it'd go away after a while but since its emergence it had gotten worse. Not only did the engine rattled crazy at start up but around town at low speeds as well.

Yesterday I took off the intake manifold to clean it, found a lot of oil in it and thought to myself may be this is the issue. The EGR system is still cleanish (cooler and pipes etc were serviced/cleaned 16 months ago). After cleaning and reinstalling the intake the car drove fine without the rattle for 100 miles and now its back. Also noticed greenish slug inside the oil cap and the coolant to be low so the head gasket is gone .

I can junk the car but it wouldnt be in me to do that, I am really busy with work/life at the moment but I have to take care of the old girl.

A couple of years ago I installed a 2017 motor in my sisters prius and kept the old bad motor as I intended to rebuild it eventually. Rather than keeping that project on the back burner as it has been over the past two years I have to hustle and rebuild it so I can transplant the motor in the car.


I watched this video last night and it helps tremendously, at least when it comes to the top half of the motor.

I'd like if folks can help me out with other resources as well that I might need through the rebuild process.I have swapped the motors in the past so thats not going to be an issue. I do need help finding what else I might need to rebuild the motor, torque specs and tolerances for the bottom end.

I plan on replacing the head gasket, the oil rings on the pistons, may be the compression rings as well seeing what condition they might be in, checking to see if the motor that I have with me has bent rods as I remember it had a bad knock before I pulled it out of the 2013 prius.

Any help/guidance would be greatly appreciated. I'd log my journey here in this thread as I go along.

 

^^ Yes, car developed a low speed knock that got rectified when I cleaned the EGR system, EGR cooler was fully plugged when I took it off.

 

^^ Congrats, I have been gathering all the info I can as far as toque specs etc. I have built motors in the past but never one for automotive application. The 4th gen swap was a breeze, the hardest part was routing all the hoses and figuring that bit out. The actual labor bit was easy.


I cleaned up one of the rooms at work where I can do all the work and pulled the motor inside, sitting under a tarp outside hasnt been that kind to it.

I will open it up in the next few days and see if there is damage thats irreparable, worst case scenario I'd have to rebuild the one in my car rather than this one. The only thing is that I trust the motor I have in my car as I have always been on top of maintaining it, even at 300k miles I am sure it looks better than how this would when I open it up and this one had only 140k miles when it went bad.

 

Valve cover is off, looks very clean in there

 

^^ This motor came out of a 2013 Prius V, I pulled it out in 2021 and installed a 2017 gen 4 motor in there, I just started the process of rebuilding this one.

This one had 140k ( I think) miles on it.

Once I pull my old motor out of the 2010 I'll rebuild that one as well, no point chucking that one away.
Although I can just replace the head gasket in mine and call it a day but I want to fix the oil ring issue as well, hence is why I am replacing the old one with a rebuilt unit.

Current plan is to do the following

- Replace crankshaft bearings.
- Replace all seals, o-rings etc.
- Replace rings.
- Inspect rods and pistons.
- Replace head gasket.
- Inspect head, get machine shop involved if needed.
- Lap valves.
- Hone cylinders.

I read somewhere about the 4th cylinder valve issue, may be I read it wrong, could someone elaborate? It had something to do with valve ticking.

 

So the current pistons do not accept the updated rings? That would be a bummer. If I have to update with a new short block then I’d just end up buying a used 4th gen.

top end is off, sadly one of the valve that was open while the engine sat outside with the tarp on it let water inside the cylinder, there was oxidation present when I took the head off, vacuumed it and soaked the whole thing in oil . I didn’t rotate the assembly while taking the whole thing off as I was anticipating this, once all the oxidation is off and I take out the pistons I’ll inspect the walls for scoring , so far it seems that the walls are good with clear cross hatching marks left from factory. Next step bottom end disassembly.

 

It’s all apart now and in very healthy condition. I honed the cylinders and it’s ready to be measured. I just need to get a hold of bore gauge to make sure it’s within factory tolerance to be used with regular rings and pistons rather than oversized.

Does anyone have access to bore tolerance numbers ?

 

Trust me it fascinates me just as much . Wife has been pushing me to let the old girl go and I told her I am just getting started lol. Once this motor is rebuilt I’ll throw it in there and rebuild the one that I am taking out.

I have figured out what I need for parts now that the whole thing is apart. I’ll place the order at the dealer on Monday and start prepping everything to be put back together once the parts are in.

 

Well, slight change of plans. Prices on parts etc are through the roof right now and after getting a second opinion on the block its not worth it for me to invest money and time into this block. I can invest the money and get this one together but after the install I'd still have my factory motor to rebuild. I do not want to build this one only to have it fail on me due to the condition of the block, do not want to spend the money on the parts twice.


I have learned a lot from the disassembly and feel very confident tackling this job. Its a shame that this block would have to be trashed due to the rust spots and pitting in one of the cylinders. I'll be taking the prius off of the road in the next day or so and start pulling the motor out to rebuild.

The oil cleaning rings on the pistons were clogged with carbon and there was varnish behind both the compression rings. I'll have pictures soon. I threw the pistons in the ultra sonic cleaner to see if that would help take off the varnish, just for laughs and giggles as I do not intend on reusing the pistons and they came out squeaky clean.