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Cooling the 1KZ-TE motor:

Lucky maybe. What year is your 90? I know toyota improved the head apparently on 99 models+. Mine being a 96 had it's head crack at about 70k miles. Dad was cruising down the motorway when he had a little loss of power and white smoke out the back. Drove like this for a good year topping up the coolant, not realizing the water was eating away at the cylinders. Long story short, it ended up having a full engine replacement.

Fast forward to about 5 years ago now, driving here in the states, one of the coolant lines blows off and the engine overheats badly. When I saw the temp gauge it was pinned to the top and I was cruising around 90-100 on the I-95. Pulled over asap and switched the engine off. After it cooled, it would run but would take 5-10 seconds to start (loss of compression). Long story short, head was warped badly, but not CRACKED. If you guys followed my thread, you know I then went on to bake/straighten this same head in my oven multiple times to straighten it and had the engine running 100% well for around 4 years, until one day out of no where it was pushing coolant back out. AMC head now on it.

So sometimes I still think it's a mystery as to what exactly causes these heads to crack. Heat, Combustion temps. The NZ chaps seem to think it's poor injectors creating hot spots during combustion. Don't know about that, I have 250k miles on my stock injectors and she "seems" fine.... What's the saying, if it ain't broke....
mines a 99, didn't know they changed the head on the KZ
Had anyone ever had one sampled and put through a mass spectrometer?
I'm new here and have been pouring over this cooling thread. I got the 3" down / dump pipe I have an EGT and a coolant gauge plus a snorkel and a 76* thermostat. I have 251000 Km's on the clock. Is there a way to see if my head has already been replaced?
You can visually look at the head and see if there are any marks. The AMC has a stamping on the outside that you can see. Not sure about other replacements though...
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Would be greatly appreciated if you could send me the email as well!

Well . . That was 2014. I'm afraid I don't have any e-mails earlier than 11/2015 and I'm struggling to remember anything about it.

My '90' has been off the road, partially dismantled, for three years. One day I'll get it back on the road but at present the '100' and the other 3 cars (plus 6 bikes) take up all my time.

Sorry, can't help.

Hi Bob,

No worries at all , thanks for checking anyway, it was awhile ago. Do appreciate the plethora of knowledge that you have offered regarding cracked heads.

I am getting mine fixed this week.

Based on reading the posts on here I have decided to do the following:

New head, by an Australian engineer who re-engineered it.
New gasket with sealant
72 deg stat.
New water pump.
New radiator.
Viscous fan recalibration and fluid top up.
Radiator flush ( reverse flush) and heater core flush. 2nd flush after new head has been put in and coolant has circulated.
After market temp gauge for better accuracy of temp.

I am hoping this resolves the overheating issue for good.

Well . . That was 2014. I'm afraid I don't have any e-mails earlier than 11/2015 and I'm struggling to remember anything about it.

My '90' has been off the road, partially dismantled, for three years. One day I'll get it back on the road but at present the '100' and the other 3 cars (plus 6 bikes) take up all my time.

Sorry, can't help.

Any info on this re-engineering head?
Any info on this re-engineering head?

Yea the head is made by a company called Engine Australia. According to the machine shop that I am buying the head from, it is owned by an Australian engineer but is manufactured in China. However, he is at the factory 6 months of the year and his son the other 6. This is to ensure a consistent quality, according to the machine shop mechanic.
Do you know what is different in the head he is producing vs the original head?
Hey all,
Definitely the best thread Ive been through regarding cooling the 1kz-te, thank you all for your input.

I have had a 98 prado intercooled auto turbo diesel for a few months now, and I am intending to get it prepared for some towing and 4x4ing.
As far as I can see, it is pretty stock. I am going to give it a full tune up, and make some changes to the cooling system.
I live in Canada, where summer can reach 35 degrees and winter can reach -35 degrees.

Before I get into that, a couple things I have noticed so far:
I go through about a liter of oil over about 1200km, no leaks on the driveway where I park, but there is some visible slight leakage from the top of the hose where it clamps around the connecting pipe of the intercooler on the turbo side. Seems as though it only does this while highway driving. Would replacing the hose, and getting better (non-spring) retaining clips sort this? Or am I looking at some other issue?

Another thing is I am hearing a rattle, seemingly coming from the passenger rear side while the engine is warming up. It seems to disappear once warm or at higher speeds. I can only hear it from the inside of the vehicle. Any ideas?

Onto cooling/monitoring:

I intend to add some gauges, what is the best recommendation between EGT, Oil pressure, coolant temp, and transmission temp? is an 'all-in-one' gauge reasonable?

I will replace the thermostat with a 76 degree one.

I will replace my 7-fin fan with a 10-fin fan.

Viscous hub seems like it is functioning properly, but I will likely buy some oil and make sure it is 100%.

A new radiator is likely in my future if I can find one at a decent price (seems hard in North American, suggestions are welcome!). It has been recently flushed. A new rad cap is probably a good idea, as well as new rad hoses.

Changing to a 3" dump seems to be a good idea, but I question whether the whole exhaust should be 3" considering the lack of back pressure that would create. Is there anywhere that offers a 3" dump that would connect directly to the existing exhaust?

Am I missing anything?

Thanks for any input, I hope I still get some activity after 3 years of a dead thread!
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Intuition tells me its the exhaust rather than the engine Toyota failed us with , a combination of heat and pressure caused by the restrictive downpipe cracks the head , correct that and the entire character of the engine changes like you have freed up a rusty hinge with a drop of oil .
Sorry th divert from the theme, is there perhaps a thread regarding the downpipe upgrading? I will try my hand at searching the forum as well.
Certainly possible to cool the engine, Auto Box and Engine Oil via separate rads. I would worry about over-cooling, but then I live in Scotland :lol:.

If you are using the truck hard in a warm climate it may be worth considering. I would be inclined to have a thermostatically-controlled by-pass on it as well though.

Another interesting photo sequence on the way . . . :icon-cool:.

Excellent thread, sir. Unfortunately my name has also been added to the "cracked head"-list! Have you posted the photo sequence as per this post of yours? I am still looking for the definitive way forward on cooling this engine! I have for one, fitted a 3-core D4D radiator to mine, but it sadly only delayed the inevitable breakdown.

No worries, I saw your reply a few posts earlier, I will also go with what intercooledkzj95 has stated and follow the same route.
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