3rd Gen JDM engine, replace head gasket or not?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by jweier80, May 26, 2025 at 2:32 PM.

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Swap the headgasket on "new" 60K JDM engine?

This poll will close on May 30, 2025 at 2:32 PM.

  1. Yes, swap it now or you'll regret it

    0 vote(s)
    0.0%

  2. No, it's overkill for an engine in that good of shape

    1 vote(s)
    100.0%
  1. jweier80

    jweier80 New Member

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    2012 Prius
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    This is my first post after years of lurking (own 3 Gen 2s and one Gen 3). I'll give you a brief back story. I bought a 3rd gen 2012 for myself 2 years ago. Presently has 272K on it. It had a misfire in cylinder 3. I did some work on it trying to troubleshoot (moving coils, new coils and plugs, etc). I thought I had it figured out (no codes for 500 miles), but the ultimately the engine threw a rod through the block and the engine is now kaput!

    I did some research trying to find a reliable/reputable JDM engine source. According to several other forums JDM Racing Motors came highly recommended. Ordering from them was simple, and delivery time to my home was surprisingly fast, and the driver even helped me run the pallet up our uphill drive way. This engine is in outstanding shape. Oil looks good. The engine overall is too clean to have simply been pressure washed by someone. Plugs are good, nothing steam cleaned or fouled. EGR is pretty clean as well. JDM tested compression before the sale. Point is I'm surprisingly feeling pretty good about the engine as it sits.

    Before the engine arrived I got talking to my dad and my uncle (the latter of whom is also a Prius fan and swapped an engine on his 3rd gen). The suggestion was made to replace the head gasket before installing the engine (along with the waterpump, pcv, and EGR cleanup). At the time I totally agreed that it made sense. I ordered parts (gasket kit, bolts, timing chain etc), and planned to do the job over the next couple weeks. But now that the engine is here I'm having second thoughts. I've replaced head gaskets in other cars before, but it's been about a decade. But I'm kind of concerned about me screwing something up on an already perfectly good engine (that at the moment...still has a warranty). Parts are easy to return...the engine not so much.

    At this point I'm just looking for what people think. Tear down the new engine and replace the head gasket now, or drop it in as is (well, with a cleaned EGR system, new PCV, and new water pump that is). Let me know in the comments or the poll. Appreciate any advice.
     

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    #1 jweier80, May 26, 2025 at 2:32 PM
  2. Tombukt2

    Tombukt2 Senior Member

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    It basically comes down to this it's all a crapshoot seriously apparently a lot of these places in Asia China where these engines are dismantled close to the docks and all that. Things can get a little crazy and send my mistreated and so on so whatever you get from that market you need to go over with a fine tooth comb as best you can generally these things are supposed to be pulled with me you know from 45 to 85k or something like that whatever that equals in kilometers I don't know there is a range most of these places selling these things in the states I don't care what their names are are just buying from one or two suppliers and that's that so all the engines basically are coming from the same place obviously via one or two suppliers and then there's all these little dealers racing shops and you know just random people whatever hustling the things markup is very good I mean you dealing with salvage here these engines are moving through the system probably $250 $300 a piece something like that on the scale that they're bringing in and what have you. But that's about the only choice you have I mean you've already got the thing so go over it real good pull the little oil pan down if you want have a look in there put it right back on and see what you got. A few people have had these things fail within a month of putting them in it has happened then again other people have put them in and never hear from them again that is the way it is these open deck design engines are fragile or more so than other designs so they can't really take a beating that's hard to tell if they've been beat on. Personally if everything looked good checked out with this I might clean the EGR while it's off make the modifications so that I can easily take the EGR cooler off and on from now on with the engine in the car lose the lower nut trim the bracket it's easy to do. And maybe clean my intake while my car's engines out and have all that ready to go and then clean my other cooler and my other intake and just put it up if I'm going to make it go of trying to keep this thing running there you go. And not change the head gasket if everything checks out well if you're really scared of it get a boriscope and have a look inside the holes. Once it's in the car it is a pain in the nice person to change the timing business and the head gasket not saying you can't do it and all that it just kind of sucks.
     
    #2 Tombukt2, May 27, 2025 at 12:08 PM
    jweier80 likes this.
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