1KZ-TE Reliability? (1 Viewer)

[Will Van]

Reviving this old thread - I know the 1KZs are known to crack cylinder heads.

Is that because they are prone to overheating? The cooling system is undersized?

Is the engine too small for the Prado, and it’s being overworked, which leads to high EGTs, high temps, and cracked heads?

Thanks!

 

[blinkerfluid]

in my experience, they only crack when engine is overheated and that happens with a cooling system that is not maintained ie bad fan clutch, fan shield not seated properly, lack of use of coolant causing rust and scaling inside the circuit and radiator

but, I've also head people saying its because of high EGTs partially due to the design of the exhaust manifold- while this can be a solid cause to the effect that heads warp and crack - i have no proof.

You can always upgrade the downpipe and exhaust manifold though

 

[F3arless]

I have got a 1999 Toytoa Hiace Super Cutsom G, 1kz-te engine in Winnipeg, the frozen north. (I think Super Custom G means electric curtains, and a small cooler/ice maker built in.) The transmission has a rad. The torque converter spewed metal dust and bits into it, and in the rebuild of the transmission I learned much from my rebuilder. 8000 kms on a new timing belt. Runs nice. But my wife's recent diagnosis of osteoarthitius in her right knee means we'll be look for another jdm that's not such a climb up...

 

[broccoliprophet]

I've put 60k kms on mine now, in Canada, where they were also never sold. And there are many examples around the world with 4 and 500 thousand kms. The JDM auction lineups are full of them...

My opinion is that they are a much more modern platform than the other IDI diesels, and very reliable. I think many of the "guaranteed" head problems stem from both the earlier LJ and the previous 1KZ without the intercooler. Heat management, like on any indirectly injected 4 cylinder boosted diesel, is paramount. But if it has been looked after, kept maintained, and driven with a modicum of sense, my experience is it is up there with Toyota's best. Just modern enough to achieve good driveability and efficiency, but old enough to be pre-DEF, and without injectors that cost a king's ransom.

I do think these are a better match to a manual trans, but that's pretty subjective. Let's just say having even more heat added to the system isn't optimum if you don't have to. Fitting an EGT guage though, is a must for any turbo diesel, I think, esp at altitude. Its easier to bleed off high pyro temps with a manual trans, but as long as you know where that overdrive button is, and are prepared to use it when necessary, AND you teach your right foot some manners, you shouldn't be imitating Humpty Dumpty with your cylinder head anytime soon.

Keeping the intake track clear of EGR soot is also important, since this machine did recycle its exhaust gases, which build up over time unless you fit a catch can or delete the egr (I'm not a proponent of emissions deletion if at all possible, and in this case it can effect the idle).

In all other respects, this truck has the reliability of a 4Runner, with an even beefier frame. Parts outside the engine and body panels are pretty much 4Runner. So that means that in addition to the head cracking every 10k kms, your lower balljoints will collapse. Or you can just change them at sensible intervals and continue to enjoy the rig for years to come.

So, if i understood correctly, 1KZ-TE engines without the intercooler system are prone to overheating. What does maintenance/prevention look like for that for '92 LC 1KZ-TE 3.0L LJ78 that doesn't have the intercooler?

 

[broccoliprophet]

1kz's only problem is cracking heads if the cooling system is not upto mark - keep the system neat and clean, radiator fan clutch good and its shroud should be perfectly placed and sealed, on these old toyotas there is usually gunk on the bottom of the radiators so a new rad will be a good idea.
Apart from the head cracking - which happens only when the cooling system is f***ed up somehow, ie low coolant, air or a bad radiator / fan - otherwise these engines are rock solid.

90 series are prone to front LCA ball joint failures, the only fix is a new Toyota ball joint.

Steering rack mounts are another failure point, replacing them with polyurethane mounts is one good upgrade - improves steering responsiveness too.

What about the 70 series that have the 1KZ-TE without the intercooler ?

 

[broccoliprophet]

Are Toyota diesels very popular in Norway? Is there much of an off-roading scene?

What about the 1KZ's in the 70's series?

 

[blinkerfluid]

What about the 70 series that have the 1KZ-TE without the intercooler ?

Same goes for them

 

[philip g]

Anyone have a radiator they recommend for a 90 series besides t-rad I have to ship from Australia or Japan?

Edit for that money I can have Ron Davis make me a custom rad

 

[JDM Journeys]

So, if i understood correctly, 1KZ-TE engines without the intercooler system are prone to overheating. What does maintenance/prevention look like for that for '92 LC 1KZ-TE 3.0L LJ78 that doesn't have the intercooler?

You'll get a lot more traction for this query in the 70 series section. Most of the 90 series got intercoolers.

 

[RudyMental666]

1KZ-TE 3.0 is a good engine if all ancillaries and add ons are in good fettle and well maintained.

I have recently replaced and upgraded some bits in/on the cooling system, I own a KDJ95 Colorado/prado.
The list is:
1. A/c condenser
2. Radiator with additional trans cooler pipes. (milner 4x4 Matlock)
3. Cambelt
4. Water pump
5. Ribbed Belt.
6. Rear heater pipes (old ones were steel and peppered with holes) renewed with copper pipes.
7. Red Antifree (Morris Lubricants)

Not a big job, but now trouble free, Thermostat was new so no need for replacement as with rubber hoses.

Reason for the replacements, was Rad had a slight leak, the condenser was in need of replacing, even though it wasnt leaking, the rear heater pipes that run to the rear heater were corroded, & all this was a recipe for big problems if not sorted..
247000 miles on a 2001 1KZ-TE 3.0 D4D KDJ95 collie
The history is remarkable, I'm 2nd owner, with FSH and original bill of sale of 30k back in 2001
Have also upgraded majority of the suspension/steering bushes to poly and this makes a big difference too, next is, suspension upgrades...

Also owned Previous L/Cs 0f 1988 LJ70 2.4td and 1981 Hj60 4.0d