"New" Gen 3 prius with busted HG

Hello,

Yesterday I picked up a 2012 prius that I found on FB marketplace. Blown head gasket, 230K, torn up seats, $2250. Pretty good deal I think. It had been posted as a plug in and when I showed up it clearly was not, so the seller agreed to actually sell it to me for $2000. In many ways I am actually glad that it is a standard Gen 3, since the inevitable battery replacement will be much cheaper. I got a Uhaul Dolly, and probably have the clerks incompetence to thank for the fact that they rented it to me with my 2.7L Tacoma, even though their website would not let me do it. There was only one steep hill that ended up being an issue, but otherwise it was actually fine. I stayed below 55mph.

I have not done a Head Gasket before, but I know to be slow, careful, organized, and watch the videos and read the threads a bunch of times over.

The 12V battery is dead, and we temporarily jumped it to get it onto the cart. I took a video of that to give a sense of what the engine looked and sounded like. I asked about the history and it sounds like:

1. A few months ago it started making an unusual noise with warning lights. It went to the mechanic and it was a misfire so the mechanic replaced (or planned on replacing) spark plugs. Coolant was found on the spark plugs, so diagnosed with a head gasket leak.

2. Sealer was put in the coolant, though that seemed to only make the smoke and sound worse.

3. It sat for a few months and then driven to the front of the driveway. Over the course of 3 days it was turned on a minimum of 3 times to show various buyers (including by me to get it onto the dolly.

I have many questions about the best order of repairs and what to keep in mind.

So far I am thinking:

1. Remove plugs and scope into cylinders to get a visual on the issue.
2. Remove injector connectors.
   
3. With plugs out do compression test (after I blast extra fluid out).
4. Drain coolant.
   
5. Remove head, cleaning as I go.
6. Replace water pump (no record on carfax of that being done).
7. Have head machined, pressure tested, and valves done. If warped too bad do I need to buy a new one?
8. Replace gasket and other seals with kit and replace head.
9. Compression test
   
10. Clean EGR and intake and throttle.
11. Reattach everything else.
    
12. Refill coolant.
13. Spark plugs back in and turn on!
14. If all good, drain and fill oil.

My other questions are:

1. Do I need to worry about bent rods? and if so, how would I be able to tell? I would hate to have to take the engine out without knowing for sure.
2. Is there anything else that I should replace/check on when I am in there? I guess it would be good to get a straight edge and feeler gauges on the top of the block.
3. How do I deal with the gasket sealer that is still in the system? It has been sitting in there, and I am worried about it clogging all the passageways. Do I just keep flushing coolant through the system? Do I not worry about it?

Here are the videos, I am sorry for the HORRIBLE filming. I was trying to document it while also getting it onto the dolly as fast as possible.

https://youtube.com/shorts/_EU_dVxuK-s

I can't get the second video to be embedded, so I just have a link ^^

 

Since I do not know how long/often it ran with this issue I do not know the extent of the damage.

I am not opposed to doing the whole engine, though I would need to get some more things for that, a hoist in particular. I have heard of a bunch of people replacing it with a 4th gen engine and making a few modifications to other parts to get it to fit. Thoughts on this? Also, is JDM worth paying more for? What parts other than the engine would I need to get new ones of? Here is a link to a JDM low mileage for $1800, but only "Electronics, seals and accessories are NOT covered. ONLY HEAD & BLOCK."

 

As I have thought about this more I am leaning in this direction -> get a JDM Gen 3 engine. I have never done an engine swap before so anything to make it easier on a first time is good. I found this video of someone putting in a JDM and he went over the one difference that he found.

One of my things was to get another prius (already have a Gen 2 which would go to parents) for cheap, but paying another $1800 or so for an engine with only like 55K on it sounds pretty nice! One thing I would need to figure out though would be a hoist. I do not own one, and would prefer to not have to buy one. Maybe there is a way to rent one? IDK. I may try to call around to some mechanics. How much does the engine weigh? A new one at Harbor Freight for 1000lbs is about $400. I would gladly pay $150 for the chance to use it or a week or so.

 

I was wondering about block and tackle. I AM in a garage with a ceiling, though renting a cherry picker sounds best if I can find one.
OK, so current plan is:

1. Rent hoist
   
2. Replace engine with Gen 3 JDM
3. Replace radiator (ideally with engine out)
   
4. Clean EGR
5. Add oil and coolant
6. START YOUR ENGINES!

There are many other smaller issues with the car, but I want to focus on the engine first. probably the next thing would be cleaning the inside and trying to deal with the trashed passenger and back seats and armrest.

 

OK, so today I had a simple plan: replace 12V, take out the space plugs, crank engine to get rid of any liquid, put plugs in, run for a while to charge HV battery since we are going out of town for 2 weeks.

Well, I took out the plugs (Autolites I see) and they all looked "fine". I cranked the engine and no coolant came out. Put the plugs back in and it started with the rattling. I went to tailpipe and there was much less smoke than before, bluer I would say? I wanted to be sure that it TRULY was a head gasket issue. I checked the dipstick, full oil (on a slant so hard to get exact), but no milkshake. Just normal used oil. Huh. Well I had heard that if you crank the engine with the coils disconnected there will be gas forced into the coolant if you have a HG leak. I tried that but no bubbles.

I was really getting curious now, so I went to NAPA for a compression tester. They were out, but they did have a block tester for rent (with the blue fluid). I thought, ah why not? So I turn on the car. get it up around operating temp (at least 160ºF) and use it with the coolant reservoir to pull air through the fluid. It says to do it for 2min, and I did it for 3 just to be sure. There was ZERO color change, indicating that there was not any combustion gasses getting in to the coolant. Wow, OK so to me that says there is NOT a blown HG.

I got limited info from the last owner, but she said that the mechanic said "It was a misfire on cylinders #1 and #2 so we replaced the coils and the plugs but the problem persisted. When we took the plugs out (not sure if this was on the first visit or a followup) we found coolant on the end of the plugs so we put in a gasket sealer to the reservoir." She claims that the car ran even worse after that visit, and it was basically parked since then.

So I get to thinking, "What else could be causing that misfire?" Could a screwed up EGR be causing that? Could a grimy intake cause that? Clogged injectors?. I started taking things apart to try and find the answers to these questions. The little connector pipe for the EGR was grimy, but I knew that the real part to clean would be too much of a job for this diagnostic. I took the intake off and that is when things got interesting. It was SO oily in there. There was a pool of milkshake at the bottom of the intake, and I recognize it as coming from the PCV since I put a catch can in me Gen 2 prius. The inside of the ports to the valves were totally grimy as well, with a film of oil on the gasket that seals it to the intake. The throttle plate was even coated on the bottom (though that may have had more to do with me taking it apart).

I cleaned out the engine ports with a rag and throttle body cleaner. I remove the injectors and swapped 1 & 2 with 3 & 4 to test if they are the problem. I cleaned off the throttle body. I removed the PCV valve and will replace it with a new one. The intake will need to wait for another day. I left things taken apart while I asses the situation.

Is it possible for this intake issue to be causing the misfire? I am wondering if there WAS a HG leak and the thing the mechanic added stopped it, but then what is causing the misfire now? I was thinking to order a JDM engine for $1550 in and install it, but what if this engine is OK? I do wonder if I should continue with that avenue, because it may be fixable now, but later on it will fail anyways. But, if it is something simple then even 6 more months would be worth it.

 

Ok, so you are suggesting that the leak is one way. I guess the only way to really find out for sure would be to scope the inside and look over at the gasket area, or to take off the exhaust manifold and see if one or two of the pipes is cleaner than the others. Is there any other way to verify this? I do not have a borescope, and would like to decide in the next few days if I need to order a new engine or not. They are cheap online, but would not arrive in time.

Also, why would a misfire be caused by a leak in the first place? is too much moisture getting mixed with the aroesolised fuel and therefor not igniting?

 

When I stuck a rod into each spark plug hole it came out basically dry. I am thinking to replace the PCV valve, and swap plugs 1&2 with 3&4. That would mean the plugs and injectors from the "good" cylinders will be in the ones that were misfiring. I guess if cylinders 1&2 still misfire then your suggestion may be the right answer. Am I hearing correctly that there would not be any real reason that the cylinders would be misfiring from issues in the intake/egr?