Gen3 engine replacement with Gen4

My son just pulled his 2012 Prius engine (blown head gasket for about a year so it was a mess) out the top and leaving the trans in place. Has now set in a 2017 replacement purchased from across the country. Still in the process of connecting everything in his spare time but wow, I am very proud of him since he had little mechanic experience. But he was motivated, being a poor college student, and refused to give up on his Prius. He used the Youtube series on replacing the Prius engine for direction. Just wanted to mention it here to encourage others.

 

His has 180k. The donor engine has about 40k

 

So do we. Based on the video series it works, though there are some relatively minor alterations like changing the motor mount to the old one, and a few others. The motor mount was one of the few things not covered in the video and became apparent in the installation. But it was a direct bolt-on replacement. So far, so good.

 

BTW, the dealer wanted $7,000 to replace the engine.

 

Edited History: He bought the car with about 130k miles on it. About 160k it started making "noises", like misfiring or a cylinder not firing, running very rough. At first, it was for very short periods but got increasingly worse over the next months, more often and for longer periods. He did finally learn how to remove and clean the egr cooler and valve. But by that time I think the damage was done, he was losing coolant. By this time he had replaced the water pump which may have been the cause of overheating and blowing the head gasket. He also replaced the plugs and coils, hoping they may be the issue. But the symptoms just continued getting worse until it finally wouldn't run. That's when he had to do something next level.

 

Yes, that was for a new Gen3 engine. I think it was a price stating they did not want to do it, but if you insist this is what it will cost you. The used donor engine with about 40k miles was about $1,100 with shipping from CA to NC.

Edit: The used replacement engine also came with the intake manifold which may have to be replaced with the old one. Not sure at this point.

 

Yes, exactly. That is what we noticed when we compared the old one with the new one. The impeller did not turn as freely, there was some friction resistance when turning it by hand. I understand this is not an uncommon finding when there has been a blown head gasket. There was never any indicator on the dash of overheating but at some point he told me the temp sensor wire had been disconnected. I hate to think the previous owner or dealer would have disconnected that to avoid replacing the pump. That would have been a relatively easy fix to prevent ruining the engine. The difference between a few hundred and multiple thousands of dollars.

 

A little help here. Since the flywheel and damper of the Gen4 engine has to be replaced with that of the Gen3 engine, what if any significance is the arrow on the flywheel?

Edit: Any suggestions on a free service manual?