SEGA64 gen4 to gen3 engine swap

Hello everyone.

So here is yet another gen4/gen3 engine swap thread. I have been educating myself with all of the other threads on here as well as YouTube videos posted by the pioneers of the modification. So I appreciate all those people sharing that information.

Just to give some context, I am not a engine guy. I’ve never done a motor swap nor am I engine savvy. My forte is suspension. I like dropping cars (coils/bags etc). So I’m mechanically inclined but just don’t mess with engines much.

So my story is pretty similar to everyone else. I bought my Prius about 6 months ago (2010/240k/4500$) I always heard that Toyota and Prius especially were bullet proof so the high miles didn’t bother me.

So after driving it for a few weeks I noticed the common vibration issue with the gunked up carbon in the manifold/EGR system etc. So I started tearing into all that and cleaned it all out. It helped the vibration but didn’t eliminate it. Then not to long after that I blew the motor. Rod blew out the front of the block and through the radiator.

After doing research on here I quickly learned that it made more sense to put the more efficient gen4 into the car rather than the garbage gen3 I have been fighting the oil gunk issue with.

I found a 2019 Gen4 that had 4K miles on eBay. A junkyard company called Benzeen Auto was the seller out of California It was 1500$ free shipping.

I end up getting the engine delivered and it was a 2016 Acura TLX engine. Turns out some other guy got my engine and I got his. They packaged them up at the same time and put the wrong shipping labels on each shipment pallet. It was a pain.

I finally end up getting my correct engine and it shows up tipped over and the straps loose. Injector connecting were broken from the tension of the pallet straps. A valve cover pin was broken. Then main harness had burnt/melted connections. Didn’t come with an intake manifold, exhaust manifold, or water pump. Luckily because of my particular situation with the motor swap, I didn’t need most of these things because the 3rd gen components would swap over. But they agreed to send me 4 ignition coils and reimburse 300$. I was annoyed and wanted to move on so I accepted. I just wanted to install the engine and get this car working again.

-INSTALL-

As far as the install goes, it’s gone fairly well. It’s kinda amazing how straight forward everything is.

The original engine has been removed. I swapped over the gen3 intake manifold, gen3 throttle body, gen3 EGR cooler/valve assembly, gen3 water pump,and gen3 exhaust manifold. I extend the temp sensor wires while the engine was out of the car. I cut the tab coming of the side of the engine block on the driver side where EGR cooler will be next to to allow for room (thanks RagingFit). I did a lot of small little bends and tweaks to the EGR cooler tubes to get the fit I desired that most others I didn’t see do. I ditched my OEM air box because it annoyed me having so much crap in the engine bay so I ended up getting a cheap intake. Also installed a new radiator since when I blew the rod through the block, it put a hole in the original one.


I eventually felt confident enough to put fluids in and start it up. I used 0W-20 Liquimoly and Peak Asian Red coolant.

I started it in maintenance mode and it cranked over and shook violently. I waited a second to see if it would smooth out but it didn’t. I was very scared I ruined the brand new motor LOL. I set up the camera to capture it doing it again and started it again and it was butter smooth. I guess it just need to work the oil through or something.

I was incredibly happy that the car even ran first try. I let it run and had the coolant resovoir raised with the cap off and the interior heater full blast. Then I hear the water but making grinding and screeching noises after the car had been running for 5min or so. I immediately turned the car off.

I just installed a brand new OEM water pump and restarted the car in maintenance mode. Again with the coolant resovoir cap off and squeezing the lower radiator hose to get the bubbles out. The car was running great in my opinion. It was idiling up and down as it should, everything sounded normal.

But this is where I’m hitting a speed bump and need help from you guys. After running for about 20-30min with the coolant resovoir cap off I noticed a huge coolant puddle under the car. I don’t know engines all that well but obviously the engine created pressure and forced all the coolant out the top of the open coolant resovoir top. Is this normal? Should it creates this much pressure. Or am I just a dumbass and needed the cap on so it could creates it normal coolant pressure the engine needs to created? Because I also noticed that the lower radiator tube stays cool but the coolant tube going into the engine on the top side driver side next to the cooler is hot. Also the coolant line at the top of the resovoir that runs along the top of the core support is hot. I’m just not that educated on what lines should be getting hot and what is normal temperature for the coolant lines to be getting. The hardest part of this entire swap was understanding and routing all the coolant lines. I triple checked them to unsure they are going to all the correct locations. I went off the diagram drawing that RagingFit provided on his YouTube channel

Sorry for the insanely long post but I wanted to explain details.


-REFERENCE PICS-

 

How so?

Because it bolts right up perfectly and the connector is the same. It swapped right over. Also if the water pump wasn’t working, how did it create enough pressure to make the coolant overflow out the top of the resovoir? I’m just spit balling here because I don’t know.

 

Because I haven’t bought more and I’m afraid of ruining something by running the car again if I have something wrong. So I’m educating myself prior to tackling it again before I break something.

 

well **** me...

 

The title says gen4 to gen3. It’s a gen4 engine going into a gen3 body. What’s incorrect?

 

I used his diagram specifically. Went over it several times tracing everything.

I think what @Dave Hanson said might be my issue. I thought for sure gen3 water pump would have no issue working on the gen4 engine because it bolts right up and is the same harness connection but apparently the impeller/shaft length is different.

If my coolant lines were wrong I feel like I would be getting codes or the car wouldn’t be running right. because it starts up and runs great. I just don’t think the coolant is getting proper flow.

I’m going to buy and install the proper gen4 water pump and try again and see what happens.

The fact these cars don’t have a engine temp gauge is insane.

 

So where I’m at now is the car starts up and runs great. Or so it seems. I have no engine lights on, my radiator fans turn on, car idles up and down seemingly normal. Only thing giving me pause is the heater/air blower works but no hot air. I have the temp and fan maxed. I have had ICE on for up to 30min in maintenance mode and it will still blow cool.

Like I said before. I’ve checked my coolant hose runs 20x in accordance to @Ragingfit diagram. I double checked that the wires for my extended temp sensor wire wasn’t flipped. I’ve installed a new water pump and thermostat. I’m at dead end with what it could be.


Thinking about just throwing a new temp sensors. And whatever this other sensor is behind the EGR cooler that’s T’d in. Can’t seem to find it online.

 

I do remember one of the hoses being hot and the other not as far as the 2 entering the firewall into the firewall.

And it was blowing hot air briefly at one point during the first ICE startup after installing the new engine. Stopped blowing hot every time after.

I’ve drained and filled the coolant system probably 6 times at this point. I’ve installed 3 diff water pumps, a thermostat, and new radiator. So yeah, lots of dumping and refilling. So maybe I disturbed the old heater core into not working. The car has 240k on it so I’m sure the heater core has gone through the ringer.