You have a good list.
I suggest looking into the JDM engines. There was just a thread on JDM engines yesterday.
MZ engines are not the easiest to rebuild reliably.
Depending upon what happened when the engine "blew", the cats may be fouled and plugged.
Replace the valve cover gaskets.
You can do a cylinder leak-down test with the replacement engine out of the car and with a little bit of work, old hoses, and some plugs, you can plug the cooling lines and do an air pressure leak test on the cooling system out of the car.
New radiator hoses and thermostat.
Depending on the age of the replacement engine, probably replace the coolant bypass hose and possibly reseal the water box cover under the intake manifold, though I hear that problem more on the 1MZ.
I would add Denso coils to the back bank, along with the Bank 1 AF sensor at that mileage if it has never been replaced.
3MZ knock sensors don't seem to fail much, but inspect the harnesses.
Depending on the condition of the replacement engine, clean or replace the oil control valves and screens and the oil pressure sensor. Inspect the oil pump screen if there is any sludge in the engine.
The power steering pumps have some failures. If in corrosion country, the power steering lines get corroded.
Make sure the transmission vent is clean. If it is AWD, clean or replace the transfer case vent when it is separated, and consider doing the campaign transfer case seal replacement.
Do inspect the flex plate and ring gear.
Alternator is easy enough to replace that I wouldn't spend the money. Starter is not that bad either. If it is running well, I probably wouldn't bother.
And I definitely would not spend the money to get lower-reliability aftermarket parts.
The 3MZ holds 5 quarts.

 

Not an expert on this stuff and don't know what year. Just naming a few things I've seen in research for other stuff. +1 on coils and sensor. I did the sensor from underneath on a 1MZ-FE with engine in the HL but I have long arms and it was still close and nerve-racking. I'd check for any grounds that could be cleaned/verified on the firewall. And clean the throttle body/IAC valve if it is being reused. Not sure if new engines come with these. Maybe wiper motors, possibly?

 

I agree with everything cr said, and want to emphasize replacing parts with denso or Toyota oem only, otherwise you will be downgrading the quality of those parts. As cr has said before in other posts, if you can’t afford to preemptively replace with oem then leave the originals in place.

 

2018 X : well this is kind of a new one. It is rare-rare-rare to hear about a catastrophically jimmied up 3MZ.
How the heck do you blow up one of these? They are pretty much bulletproof.
All the best, Haya....

 

About JDM engines

Picking up a 2006 Toyota Highlander with 2.4L

Overheated with 150k miles. No compression on cyls 2 and 3. What would you recommend how to proceed to get it back on the road? 1. Replace just cylinder head, gasket, head bolts and radiator. Where is the best place to get a reman cylinder head? 2. Find a low mileage used engine (

www.toyotanation.com

 

Thanks for the replies. I love this site! So many knowledgeable and helpful folks!

I feel more relevant background info is in order:

My friend recently acquired the vehicle about 5-6 months ago. It used to belong to his cousin for about 3 years. Prior to that, heaven knows what the history is. It is a model year 05 or 06.

As HayabusaFalcon correctly pointed out, The MZ series are sturdy ultra reliable and smooth mills WHEN proper maintenance is preformed. The reason my friend is in this mess is because it is quite clear that proper maintenance, specifically oil changes every 3-5K were not performed throughout the life of this vehicle.

This thing was burning/consuming a lot and I mean A LOT of oil. The engine grenaded on the highway due to lack of lubrication. The car has no oil leaks. The dipstick was dry!!! He had the oil changed about 3 months prior to the event in question. The MZ are susceptible to oil burning/consumption issues when the oil isn't changed on time.

CR- Thanks for the awesome and detailed reply! I have no reason to believe that the cats aren't fouled up due to the oil burning/consumption issues the original motor had!

The place we plan on sourcing the motor from sells the complete fully assembled longblock (bottom end and cylinder heads) and it comes with a box of new gaskets that are needed to complete the job. I have to see check if that includes the valve cover gaskets. The motor has a 2 year unlimited mile warranty. There is 0 miles/hours run time on the replacement motor. Just gotta transfer over the accessories and what not.

The reason why I mentioned the knock sensors and harness is that I religiously follow AMD the car care nut on youtube. When ever some mentions changing knock sensors on the MZ, he always advises to change the harness as well in addition to the sensors because with the location of the harness, it is exposed to lots of heat and gets brittle as the years go by.

We will definitely add the coolant bypass and radiator hoses to the list.

(Smacks forehead) How could I forget about the 3 rear coils! That is a good point about replacing them and we will certainly use Denso coils!

Question about the 02/af sensor. I know on a longitudinally mounted engine, bank 1 is the drivers side. On transversely mounted motors such as this, is bank 1 the radiator or firewall side?

I freely admit I don't know as much about the MZ motors as the 2GRFE as that is what propels my Avalon. I have no idea what a water box cover is. I'll assume you aren't referring to the coolant overflow tank?

We will definitely clean the tb and intake plenum.

I'm assuming the oil control valves and screens are in the heads correct? I would assume that the re builder would have replaced these parts but I will definitely follow up and ask him about those. We will add the oil pressure sensor to the list.

I will get back to you about the power steering stuff in a separate post. I've got questions.

We will make sure the vent on the u151 is clean. Fortunately, this HL is FWD so he doesn't need to worry about the 4WD related components.

We will inspect the condition of the flexplate and ring gear. We wont worry about the alternator and starter.

You know, I will definitely have him get the factory service manual for the gen 1st gen HL. I just ordered a cd of the factory service manual for a gen 7 camry for myself ( the 4th gen Avalon and 6th gen ES are mechanically pretty much the same car and are derived from the 7th gen Camry)

By suggesting looking into JDM engines, you mean sourcing a 3MZ from Japan? I will read the thread you linked to.

CR, thanks again for the detailed post. Lots of helpful info to chew on. The knowledge you shared will definitely come in handy with this upcoming build.

osgoodconklin- we will clean the tb and will check the grounds.

Mgeorge- we will use Denso/Aisin parts whenever possible. thanks for the tip.

 

Question about the 02/af sensor. I know on a longitudinally mounted engine, bank 1 is the drivers side. On transversely mounted motors such as this, is bank 1 the radiator or firewall side?

Bank1 always has cyl 1. And of course cyl 1 is on the firewall side of the engine on the MZ

By suggesting looking into JDM engines, you mean sourcing a 3MZ from Japan? I will read the thread you linked to.

Yes. JDM is Japan Domestic Market. Good used engines typically low miles at junkyard prices.
But if you have a rebuilder who does MZ engines at a good price, that is good too.
There are a couple of gotcha's on MZ long block rebuilds that I would ask how they handle.
First, ask how they are dealing with the cylinder wear. The steel liners are very thin - cannot be bored. Toyota says to throw the block away. A large reman facility might make their own sleeves, but a small shop? Then again, I have learned to never underestimate a determined individual with a mill and lathe. Or even a hone.
Second, getting the main bearing clearances right - it takes a lot of plastigage.
There are about 20 entries in the reference table and 4 bearing sizes
And these bottom-ends are very high performance 4-bolt mains.
Reference:

• legendary 1970 Plymouth 440 CID/6 barrel muscle car: 0.89 hp/cubic inch.
• 2004 Highlander 3MZ-FE 300,000 mile grocery getter: 1.09 hp/cubic inch

Third - there are no cam bearings. Did they just leave it?
Fourth - for the valves, there are about 1500 entries in the valve shim table.

 

As for the knock sensors, they don’t seem to be much of a problem on 2004 and later engines, mine have 293,000 miles on them. You can certainly change them for peace of mind, though.

 

Mgeorge is correct, based on my observations. The 3MZ knock sensors seem to be more robust. The design of the knock sensors was changed for model year 2004. The 1MZ-FE knock sensor is a narrow band resonant type tuned to the knock frequency. The 3MZ-FE knock sensor is broadband, covering over an octave. My understanding is that the tuning of the PCM is different, so the 3MZ-FE knock sensor is not backwards compatible. The 1MZ sensor grounds to the head. The 3MZ sensor grounds in the PCM.
Note that the orientation of the 3MZ knock sensor is important to keep water out of the connector.

 

To answer your question, on my 2003 1MZ-FE transverse mounted (timing belt on passenger side), the bank 1 O2 was on in the exhaust on the back side of the engine. Not sure about the 3MZ though. Probably the same unless it's not. Good luck!

 

You probably know this, but also ask for their recommendations for a break-in oil and first oil change interval.
You said this is a long block, so I assume it does not come with valve covers. Best wisdom on the forum is that the transition to the rear valve cover with the new baffle design occurred sometime mid year 2005. The older design seems to be much more prone to sludge buildup. I would spend the money to get the new one. Only the rear (bank 1) is needed. TheLowlander has a recent thread on the valve cover, and there are others.
And personally I use the severe service maintenance recommendations because I believe it is what the engineers originally recommended, but I change oil between 2000 and 4000 miles, depending upon season and how much of my driving is short trips.