Why are Toyota 1KZ-TE heads so crap?

1ollie, May 2, 1:45pm
x1
Its pretty well known that the Toyota 1KZ-TE 3L turbo diesels are pretty average when it comes to reliabilty in the head department but does any one know why!
I have done quite a few head swaps or repairs on them over the years, but recently I have been completely amazed by how crap they are again as about two months ago a freind was looking at purchasing a mid 90s Super Custom with 160 odd kms on the clock which had major head work done 3000+ks ago with just under $4000 worth of receipts from a reputable workshop for brand new STA(Chinise) head and all the related common things, I went with him to look at it, we did coolant leak/presure test, compression test and few other checks and motor acted like new, everything seemed legit like reciepts, records, kms etc so he purchased it and he even got me to do a EGR removal after he got it as thats a rumoured problem with these motors.
Anyway now fast forward to last week which is about 4-5000kms later he went to do an oil change an at the same time he checked the coolant an it was down by 700 to 1000ml so he toped it up then decided to check it a few days later, it was down again, was presurising the coolant system on free rev, so we took the head off, got it checked, it was soft and had a mild bow/warp in it! yes ive looked at everything related to the block that you can do in place like checked its flat with a good strait edge, looked for any damage anywhere etc and it seems mint.
This is far from the first time ive seen and heard of storys like this! so yeah. does anyone have any ideas!

snoopy221, May 2, 4:53pm
Endof the day ya lookin at the ole 202 holden--or 3.3 vicyta or 2 fiddy coon and JUST HOW FAR ya can go upz zee hill in top gear

[Kiwi mentality-if itz wkn ya not lookin at zee gauges-k]

And with a bottom hosed thermostated engine-ya'll naff it

Appens eaps-120 horsen power and 1000 horse cooling on load after (x) miles and lack of maintainence.

However there are a few japper heads that have been short on structural lonlglevity

But -they always were inherently not that robust-even in the top stat dayze we used to pull em apart and triangle brace and "O" ring em.
back in the shell sport datsun 120Y! dayze.
lol-oh and 120y's wern't known fer pinging gskts-

BUT 69 HORSEPOWER VERSUS 200 HORSE=

Well late model import clogged cooling system NON FAIL SAFE THERMOSTAT and kiwi
TUDE.
I. E.

AS in the olde oldenzzzzzz
OVERLOADING OR OVERSPEEDING MAY VOID YOUR WARRANTY

gadgit3, May 2, 7:32pm
x2
STA heads are turds.plenty of engine builders have shyed away from them.
The biggest problem with the KZ is the cooling system is not keeped up to spec and I dont just mean the core of the radiator.
The viscous fan playes a huge roll in cracked heads on these engines.

beast9, May 2, 7:47pm
also an increase of the exhaust profile helps stop the problem on the 1kz-te and also the old l series engine all the nelson 4wd clud members that run toyotas have put 2.5" exhausts into there wagons with performance mufflers and no problems reported yet

r15, May 2, 7:54pm
x1
I know why.

They aren't idiot proof.

They only crack when overheated.
don't over heat it and you wont have any problems.Look how many vehicles there are around with 400000 plus km with this engine.

r15, May 2, 8:01pm
x1
Usually the problem boils down to one of these issues.

Owner refuses to believe radiator is blocked and thinks a liquid flush is enough

The viscous fan needs adjustment or replace.If you can gear it working then it isn't working as much as it needs to

Lack of transmission cooler dumps even more heat into already ineffective cooling systems.

A worn torque converter will highlight this even further

The factory gauges are very slow to react to increases.This means the clueless layman wont notice until too late.

People believe getting hot is ok as long as it's below the red line.

intrade, May 2, 9:06pm
i fitted a old engine in my hilux from 1982. The japanese diesel went down the gurgler in 1988 when they changed the cilinderhead from rocker -rollers. and slapped on egr. Only drive euro-diesel and guess what not one ever craked a head . the renault is most warnarable to distruction due to its fully alluminium designed engine block.
Its design combined with poor R&D that makes toyota diesel heads crack. worst one is the 3c-t engine fitted to enemas-lucidas they all crap out no matter what you try and do to prevent it.

studio1, May 2, 10:39pm
x3
The 1KZ-TE engine (and head) is as reliable and well made as any other good Toyota engine.
There's an issue with 2L-T heads cracking as well (although you don't hear about it much now due to them being quite old).
As mentioned above, a lot of it comes down to poor maintenance, failure to ensure coolant is fresh and topped up and not looking after the radiator.
As correctly stated above, the cure for it is to fit a larger exhaust. Heat build up in the turbo (not being able to escape away from the head) is the main cause of cracking. Once a bigger exhaust is fitted, no more problems.

1ollie, May 2, 10:53pm
x1
Thanks for the replys few good insights and ideas.
I can not comment on how it was driven as I was not there 99.9% of the time but I don't think it would have been thrashed or driven in a stupid way as the guys not like that but only he knows I guess.
In this case it isint the cleaness or conditon of the cooling system thats for sure! as the litttle radiator was checked, cleaned & flow tested and the main radiator was re-cored with a brand new core also at the same time an aftermarket trans cooler was fitted and the viscous fan is in good condition.
Still the fact is the same thing happens to genuine heads very often but thats an interesting thing about the "plenty of engine builders have shyed away from STA heads" I would not be surprised really I guess so maybe in this case thats all it is. just a rubish replacement head.
Also I have never seen a 1KZ Hiace with more than 300km on the odo but not saying there is none as clearly there will be a few! but also I have never seen one thats over 230km thats had no head work at all but once again not saying that there are none!

1ollie, May 2, 11:00pm
Also I dont believe for a second any of the 2L 3L 5L series has anywhere neer as many problems like these do! from my experience they take way way more abuse with less maintenance and do way more kms without as many problems 'WHEN COMPARED' to the 1KZ-TE! sure they are no wonder motor but are much better.

gadgit3, May 3, 12:06am
Another thing to check is the waist gate actuator isnt seized as over boost will increase combustion temp and this can also cause the cracking.
The cracks apper under the pre co's and it is a water jacket breach to inlet track.

quater, May 3, 12:57am
Long gone are the days where the toyota would sit at the back of the farm for years ready to start everytime, bit of a bash to the fender to give it the clearance it once had. If other cars don't need as much servicing dosen't that make the 1KZ-TE a lemon!

steve312, May 3, 1:11am
Main problem with all of the 4 cyl turbo diesel engines is that the cooling system is just big enough for the engine under normally load and operating conditions.All you need is a slight cooling blockage, a viscous that is a bit tired, a slightly restricted exhaust or when you really start to work the engine and everything can't keep up.The heat builds up faster than it can manage and the engine overheats.There aren't many engines out there that can stand being overheated.

gadgit3, May 3, 1:17am
It's a alloy head on a cast block. No different to the 2.5TD ford/mazda and the 4M40 mitsi and they all have the same issue when the cooling system fails

quater, May 3, 1:25am
x3
By the way if anyone needs 1kz-te parts, i got some the head is no good tho.

Anyway, here's what I know about the Toyota's 1KZ engine. It is a diesel engine that has been used in a variety of Toyota vehicles around the world. Some of the common problems that can occur with this engine include:

Glow Plug Failure: Glow plugs are used to heat the engine block before starting, and can fail over time. This can result in hard starting, especially in cold weather.

Fuel Pump Failure: The fuel pump can fail due to wear and tear or clogging, leading to loss of power, rough idle, or stalling.

Overheating: The 1KZ engine is prone to overheating due to a variety of factors, such as low coolant levels, a malfunctioning thermostat, or a clogged radiator.

Oil leaks: Oil leaks can occur from various points in the engine, such as the valve cover gasket, oil cooler lines, or oil pan.

Turbocharger Failure: The turbocharger can fail due to oil contamination or a buildup of carbon deposits, leading to reduced power or a complete loss of boost.

To deal with these problems, it is important to follow the manufacturer's recommended maintenance schedule and address any issues as soon as they arise. Some of the solutions to these problems include:

Glow Plug Replacement: Glow plugs should be replaced at regular intervals to ensure reliable starting in cold weather.

Fuel Pump Repair or Replacement: A failing fuel pump should be repaired or replaced promptly to prevent damage to the engine.

Overheating Prevention: Regular coolant flushes and maintenance of the cooling system components can prevent overheating.

Oil Leak Repair: Oil leaks should be diagnosed and repaired promptly to prevent damage to the engine.

Turbocharger Maintenance: Regular maintenance of the turbocharger, such as cleaning or replacement of the air filter and cleaning of the turbocharger itself, can prevent failure.

Hope this helps!

elect70, May 3, 3:36am
x1
Crap materialthe alloy is mixture ofaluminium& lead fromscrap batteries & otherscrap metals .Few excepttop euros usepure hi silicon alloy .Even scrap metal dealers give you FA for themcall it muck metal .

franc123, May 3, 8:59am
Yep that about sums it up. The other thing that people forget is that towing trailers is a completely foreign concept to the japs, they just don't get it and don't engineer for it. Thus most vehicles are fitted with these cheap crappy single core radiators, you need twins or preferably triples if you can fit them in and they are available. The sheeramount of insulation and shielding in the engine bays doesnt help either re heat dispersion.

franc123, May 3, 8:59am
Yep that about sums it up. The other thing that people forget is that towing trailers is a completely foreign concept to the japs, they just don't get it and don't engineer for it. Thus most vehicles are fitted with these cheap crappy single core radiators, you need twins or preferably triples if you can fit them in and they are available, ditto decent trans coolers. The sheer amount of insulation and shielding in the engine bays doesnt help either re heat dispersion.

guest, Jul 6, 9:54am
was prob soft before you put it on poor quality chinese head

alex, Apr 23, 10:11am
x1
my surf started heating up this after noon and went down again on the heat gage and up a little but the highest point it got to was half way between operating tempurture and the red line and the radiator was pressurized filling the collant tank up. i then checked for a thermostat because i thought that could have been faulty and it did not have one and does anyone have a idea what the problem is and the oil was not murky either but normal colour