Updated February 23, 2016
I own an LJ78 Landcruiser Prado (2LTE), and I love it. These vehicles are very well built and generally as tough as other cruisers with the exception of the small IDI turbo diesel 2LTE engine. I feel they are one of the most undervalued and unappreciated cruisers out there. Fix the engine issues, and you have a winner. With the exception of the engine and rear axle the light duty cruiser shares almost all major parts with the heavy duty cruiser lineup (1990+ 70 series and 80 series).
I think everyone knows that these engines are prone to overheating under high load conditions leading to cracking the head between the intake/exhaust valves into the coolant passage directly above. Head failure usually occurs when steam pockets form in the coolant passages in the head. The steam pockets cause uneven temperatures in the head (hot spots). Uneven temperatures cause stresses in the head which lead to the metal cracking. Poor maintenance will accelerate the problem. To understand how to prevent overheating issues, we need to understand exactly what is happening that leads to the problem.
The Prado was marketed as a light duty luxury sub-urban SUV in Japan, thus it was given a small quiet engine and soft coil springs with luxurious interior options, while retaining many of the components from the heavy duty land cruiser lineup. The 2lte engine is an Indirect Injection Diesel. This means it has a pre-combustion chamber in the head. This design was used in smaller consumer vehicle engines as it reduced diesel knock noise, and increased the usable power band. The main disadvantage with this design is that it is thermally inefficient. A large amount of heat is lost through the pre-combustion chamber into the coolant passages in the head.
On non-turbo diesel engines, the IDI design works very successfully. The entire non turbo series of Toyota L engines (2L, 3L, 5L) are known to be very reliable and long lasting with no over heating problems; yet they share the same head design as the turbo engine!! When a turbo is added with the accompanying extra heat (compressing more air, burning more fuel), the IDI engine becomes seriously disadvantaged. It is not mere chance that Toyota's only two IDI turbo diesel truck engines (2LTE and 1KZTE) both have head cracking issues, while the DI (direction injection) turbo diesel engines (13BT, 12HT, 1HDT, 1KDT etc..) are known to be very reliable with no cracking problems.
Toyota further aggravated the 2LTE IDI problem by maintaining a very high compression ratio, adding an emissions system, adding an electronic injection system, neglecting to intercool the engine, and using a small undersized fan/shroud. All of which add even more heat to the system than is necessary. They then put this small displacement 95hp engine into a 2200kg vehicle with a slush box auto transmission.
Add to that poor maintenance by the original owners in Japan, and we have a perfect storm. One wonders how the little motor lasts even as long as it does!!
So how do we counteract this turbo diesel IDI heat problem? There are three ways, one use a waterless coolant that does not allow steam pockets to form. Two, reduce the heat being absorbed into the head/coolant in the first place. Three, increase the heat being removed from the coolant.
I have discovered the 2LTE can be made into a sufficiently reliable, cool and powerful engine with the right modifications and driving style. I have done many modifications on my engine (with good success), and have shared my notes/experience below.
Disclaimer: The following mods may not be for everyone. I'm just sharing my experiences with the 2LTE. Feel free to add your own ideas to this thread, or criticize what I've said. I'll add to this thread as I further mod my engine and discover new ideas.
Following is my recommendation to anyone that already owns a 2LTE and would like to improve it:
- Download and read the manuals!
- This is a Denso manual that explains in detail how the 2LTE electronic diesel works. It's an excellent read:
V 3 P5ZGR01.pdf
- These are the engine manuals for the L series engines. They do not cover the electronic injection system, but everything else is applicable to the 2LTE motor:
RM520E (Main for 2L, 3L & 5L engines)
Dropbox - 2L 3L 5L ENGINE RM520E.pdf
RM582E (Supplement for 2L, 2L-T, 3L and 5L engines)
https://www.dropbox.com/s/1joci2o0xtg6ujv/2L%2C2L-T%2C3L%2C5L ENGINE SUP. RM582E.pdf?dl=0
Finally, if it's a Prado you are working on, here is the manual that covers the rest of the vehicle (RM183E):
_KZJ70_HZJ_PZJ_chassis_body.pdf
This is a Youtube video that explains how the 2LTE injection system works:
- CHANGE TO A WATERLESS COOLANT!! I have done every modification below (except a turbo upgrade), and finally went to Evans High Performance Waterless Coolant in the Spring of 2015. I have to say, I am confident that this stuff is the ultimate protection against cracked heads in the 2LTE engines. If a person were to do NOTHING else (except basic maintenance), and only went to waterless coolant I have full confidence their cylinder head would never crack. The conversion will cost minimum $250 in coolant/flush agent alone, and is quite a bit of work. It is critical that all the old coolant/water be removed from the system for the waterless coolant to work correctly. I have put this stuff through the paces towing my 16' camper trailer and even running up to 240F coolant temps, and it works super well. I can't say enough about this stuff. Every 2LTE on earth should be running it. Note, your engine will run warmer with it, as Evans is not as efficient at transferring heat. This won't matter though, as the stuff does not turn to vapor until 380F!!! There are people on Mud that have run up to 270F on IDI engines (running Evans) with no ill effects!
- Install an EGT gauge immediately, and never allow post turbo EGT's to exceed 1000F. Drive accordingly. Always shift down on the hills to bring the rpms up. On the worst hills, keep the rpms between 3000-4000, and you'll see a big drop in EGTs. NEVER shut the engine off without proper cool down. Use your EGT guage and water temp to judge proper cool down time. Personally I let mine cool down to less than 400F post turbine on my EGT gauge, and ensure I'm at normal coolant temp before shutting the engine off. If really hot, turn the manual throttle control to 2000rpm to help the engine cool down faster. Generally after an easy drive this is a few seconds, after a really hard run it can be a few minutes.
- Buy and install a good quality aftermarket temp gauge. Never allow the engine to overheat (with regular water mix coolant). These engine will not tolerate being over heated. With the factory gauge, do not exceed the halfway mark. With an 82C thermostat, the gauge should be sitting around 1/4 normally. An 88C thermostat will put it around 1/3 normally.
- Bring all engine maintenance up to date:
- Oil change/filter,
- Fuel filter,
- Air filter,
- Coolant system service (pump, hoses, rad service if needed, new thermostat (82C), rad cap, new Toyota red coolant - or go to Evans High Performance Waterless Coolant as discussed above)
- Check clutch cooling fan for correct operation, replace it if necessary, or at least replace silicone oil in it. This is VERY VERY important. Check that the spring is intact. Open the unit, replace the fluid with 50ml of 10,000Cst Silicone oil, and test the turn on temperature.
Blue fan clutch mod
- Add redline water wetter to your coolant (water based coolants). It reduces the chance of bubbles forming in the hot spots of the head. It's cheap, and may save your engine.
- New ECU coolant temp sensor
- Injector service if needed
- Injection pump repair if needed
- Timing belt job if needed
- New glow plugs if needed
- Turbo rebuild if it needed
- And of course make sure the rest of the vehicle is in good shape so as not to make the engine work any harder than it needs to (no dragging brakes, under inflated tires etc.)
- Do the free/cheap modifications first to reduce EGT's and improve power/efficiency:
- Remove the entire intake system from the turbo to the head and clean the sludge out of it. Also clean the sludge from the intake ports and valve stems in the head. Mine had 3/8" build up. The sludge is caused by emissions systems (EGR/PCV) dumping crap into the intake of the engine. The result of this sludge is that less air gets into the engine, making for a rich burn. A rich burn causes high EGT's, which in turn make for a hot/stressed head.
- Prevent future buildup of sludge by installing a PCV catch can, or just venting it under the vehicle (like the old cruisers did), and
- Remove the EGR system (all related pipes, VSVs, vacuum hoses), and fabricate/install block off plates at the exhaust and intake manifolds. Removing it will prevent sludge, but will also prevent hot exhaust gasses from feeding back into the intake.
- Remove the throttle plate in the venturi/throttle body. The throttle plate is there primarily to make the EGR system work. It also makes for slightly smoother idling and shutdown (again, a luxury thing) Removing the throttle plate will eliminate throttling losses, and thus allow better power at all throttle positions less than wide open. As it allows more air into the engine, EGTs will be reduced further. Throttle response and cold starting will be greatly improved. Do not remove or tamper with the throttle position sensor while doing this job!! (or it will need to be re-calibrated)
- Upgrade the undersized factory cooling fan with a larger one (such as the Toyota V6 'ring fan'). This will require a custom spacer or different fan clutch/hub to prevent the fan from interfering with the crank pulley and fan shroud. I have discovered that when Toyota shortened the front end design of the 70 series to the softer look of the Prado, they really screwed up the cooling and air flow capacity. There is not enough room for a proper shroud and fan. There is no where for the air to go behind the fan, as the engine sits too close. This I've found is one of the big mistakes of the Prado design.
- Upgrade to a high flow air filter. There is a K&N factory replacement filter available; not recommended for extreme dusty conditions though. However works perfect on highways. Allows more air into the turbo for cooler running and increased efficiency.
- Install an adjustable bleed valve on the vacuum line leading to the electronic boost sensor (there is a thread by pradocruzer on how to do this). The bleed off valve will trick the computer into thinking there is less boost than there really is, meaning there will be less fuel injected, and thus lower EGT's. Tune the bleed valve for good power and low EGT's. The tune of this valve will change depending on the work you do to your engine.
Reducing 2lte egt's
- Increase the boost to 12psi using an Ebay manual boost controller. More air means lower EGT's. Don't turn the boost up beyond 12psi without an intercooler though, as the increased turbo heat will be negate any advantages of the increased air volume. With an intercooler, you can basically run as much boost as you want/can. I run 16psi, which seems to be about the max I can get with my setup.
- If auto, add a transmission cooler in-line before the radiator trans cooler.. This will reduce the amount of heat that the radiator has to dump. The trans oil will still need to run through the rad to maintain proper operating temp though (otherwise it would likely never get up to proper temp). The torque converter while out of lock-up will generate a substantial amount of heat which is transferred into the radiator. Once your engine is setup to make more power, you can stay in lock-up up hills and thus generate less heat.
- Run an 82C thermostat instead of an 88C. This will give a little more head room with engine coolant temps.
- For technically advanced owners, there are correction resistors on the fuel pump that effect injection timing and volume. Read the manual I posted above to understand how these work. I cut the wires for the resistors at my ECU, and installed my own adjustable resistors (potentiometers). I played around with this quite a bit, but in the end I found for my application that the factory resistors were actually the best values for power/temperature/efficiency. Don't advance the timing too much, or you will cause damaging diesel knock.
Do the expensive modifications to lower EGT's and improve power/efficiency:
Exhaust:
- Replace the entire exhaust system with a good quality free flow 2.5" or greater diameter system. I welded up my own aluminized mandrel piping with a Aeroturbine 2525xl, and it was a huge improvement.
- Buy or fabricate a dump pipe to remove the worst exhaust restriction which is at the output of the turbocharger. I have not done this yet, but did bore out my dump pipe which helped a lot.
- Better flowing exhaust/dump pipe lowers EGT's further. In my application, it dropped max EGTs by 150F
Intercooler:
- Install a front mount intercooler (more efficient than top mount). Pradocruzer demonstrates a highly efficient air/air front mount intercooler system which requires removal of the A/C. See post #6 here
How to Install a Intercooler on a '91 Prado EX5 (2L-TE)?
I went with a water to air intercooler system so that I could retain my A/C. Here are details on my setup:
LJ78 Air/water intercooler working! It dropped my EGTs by at least 250F max. This allowed me to crank up my boost and fuel all they way, and really transformed the power of the engine. It ran cooler and made at least 50% more power.
- Add a snorkel to gather cooler cleaner air near the top of the vehicle. This apparently can lower EGT's, and increase fuel economy. I have not yet done this, but will when funds permit.
- I have experimented with water/methanol progressive injection. In theory this can greatly reduce EGT's (water), and increase power (methanol). Some of the advanced kits only turn the system on at a pre-set EGT level, and then progressively increase injection volume with boost pressure. I installed a Devil's Own 250psi progressive system. Power was definitely up, but I have not seen the reduction in EGT's I was expecting. Perhaps I just need to play with it more.
My 2LTE is an alcoholic
- Finally, if you have deep pockets, upgrade to a more efficient turbocharger as the factory unit produces a lot of heat at higher boost levels (as it moves outside of it’s efficiency range). A modern turbo from a 2.0l-3.0l displacement diesel engine would work well. Perhaps a Garrett GT2052 or similar. This will require custom fabrication etc.
- Tune the engine by way of the, boost controller, the spill control valve screw, and the boost sensor bleed valve. A final tune might be best done on a dyno. The above modifications will cool the engine down so much that it becomes possible to make significantly more power.
Feel free to post in this thread if you want more information on how to implement these modifications, and I'll try to answer your questions.
Here is my engine with pretty much all the mods listed above (except snorkel and new turbo) done to it. It is completely transformed from the lump I first bought. Unless towing I don't have to look at my gauges at all anymore. I can travel up 8% grades (often in OD) at 100km/h with my vehicle loaded with passengers/gear without high EGTs or water temps.
Anyways, once the new turbo is eventually up and running I'll post my thoughts. I've heard mixed things regards their reliability, but it seems they do offer a performance improvement over OEM.
turbobits.co.nz
