1KZ-TE Cooling Info

[george]

If all goes well I will have my KZ in a weeks time.
I think the only problem is the Head cracking issue which is widely discusses on various forums.I found a link wich I think is quite interesting.I will have to read it a couple of times to grasp it fully.I would like to hear some of your thoughts on this.
The one thing that I picked up was that a 76 degree thermostat is MAYBE better than the standard 82 degrees.What do you guys think about it after reading this link
http://www.landcruiserclub.net/forums/s ... Z-TE-motor

[JohanW]

I replaced my kz-te thermostat about a month ago with a genuine one from toyota. The one i was given by toyota was an 82 deg one. The one i took out was a 76 deg one... same brand (ntc i believe) My kzte head was replaced by the previous owner.

The reason i replaced my thermostat due too it taking too long to get up to temperature. Its the first sign of a busted thermo. If it cant close correctly it cant open up fully either. My kz-te gets up to temp really quickly now. I plan to monitor the temp this coming summer and replace it with a 76 deg one if necessary.

With the 76 deg it never took too long to get up to temp and stayed there. Temp needle never moved from halfway.

I fully agree with the posted article.

[george]

Thanks Johan.How much kilo's is on your truck?

[JohanW]

248843km just checked this morning

Replaced top gasket and skimmed the head end June. Gasket blew Dec 2012 only discovered it in middle Jun. Did the entire rebuild myself. Cost about R2500 parts and consumables wise.

Pressure test on radiator is the easiest way to determine if the head needs attention.

[george]

248843km just checked this morning

Replaced top gasket and skimmed the head end June. Gasket blew Dec 2012 only discovered it in middle Jun. Did the entire rebuild myself. Cost about R2500 parts and consumables wise.

Pressure test on radiator is the easiest way to determine if the head needs attention.

[george]

Over the weekend I looked at a 2005 Legend KZTE.It was a 4x2 but I did notice that Toyota blanked the radiator cap and moved the cap to the reservoir bottle and have a screw on cap.Maybe one of the weak points is the radiator cap on the older models.
Just out of interest sake does the face lift models also suffer the same fate.?

[JohanW]

Just an update, went up to Vanrhynsdorp and the maskamberg this past weekend and returned yesterday. The kz-te is definitely running hotter with the 82 deg thermostat. You can smell it running hotter too, especially after a hard run in LR 1st with difflock on up a 100m steep cross axle holed mountain.

I will be replacing the the 82 with a 76 deg one. Did the same hill with nearly the same load and outside temp with the 76 deg one without it being smelly.

The temp gauge is in about the same position compared to the 76 deg. But we all know these gauges are as sensitive to temp as a ten pound hammer is to rocks.

Now to find a 76 deg one... Masterparts doesn't have, i doubt that toyota will supply one.

Anyone know?

[george]

Just an update, went up to Vanrhynsdorp and the maskamberg this past weekend and returned yesterday. The kz-te is definitely running hotter with the 82 deg thermostat. You can smell it running hotter too, especially after a hard run in LR 1st with difflock on up a 100m steep cross axle holed mountain.

I will be replacing the the 82 with a 76 deg one. Did the same hill with nearly the same load and outside temp with the 76 deg one without it being smelly.

The temp gauge is in about the same position compared to the 76 deg. But we all know these gauges are as sensitive to temp as a ten pound hammer is to rocks.

Now to find a 76 deg one... Masterparts doesn't have, i doubt that toyota will supply one.

Anyone know?

Thats good to know.Let us know if you find one and where

[Thabogrobler]

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[Sun Chaser]

Hi George
I replaced my head quite a while ago and all was good until i started to tow a boat end of last year, lack of power and overheating. I finally got the overheating resolved with a larger radiator, from a Prado, it has an extra core as I understand it. Allan at AEW Motors did it for me. I've just done Khadoum in eastern Namibia, hours of low range driving and no heating issues at all. I think for the KZTE, the bigger radiator is definitely the answer, and will save your head. MTCW
Ian

[george]

Hi George
I replaced my head quite a while ago and all was good until i started to tow a boat end of last year, lack of power and overheating. I finally got the overheating resolved with a larger radiator, from a Prado, it has an extra core as I understand it. Allan at AEW Motors did it for me. I've just done Khadoum in eastern Namibia, hours of low range driving and no heating issues at all. I think for the KZTE, the bigger radiator is definitely the answer, and will save your head. MTCW
Ian

Thanks Ian.

[JohanW]

Now that you mention it Ian, I have also got a different radiator in mine. seems bigger. Its got a radiator king sticker on it. Will have to go look and see what size it is.

[JohanW]

So, head over to toyota in lunch to ask about a 76 deg thermostat. Intially they swear high and low that a kz-te only has one type of thermostat. A 82 deg one. So i tell them i took out a 76 deg one from my bakkie when i replaced it. They go silent... So we have a look on the computer. A 2000 model Kz-te only has one type of thermostat listed. I tell them it is a NTC branded thermo and must have come from toyota themselves.

Brainwave, see if the 2004 model kz-te also has only one type of thermo...

It has two

But unfortunately the temp is not listed on this other type. Its also a bit more expensive. The other option on the 2004 model has the same part number as 82 deg one. So by logical deduction we decide to order this mystery thermostat to see what temp it is.

Should receive it by Monday.

Now the question is... did the 2004 kz-te come with this mystery thermostat fitted? is it a 76 deg one? Could this explain why the 2004 kz-te motors have lower head failure rates...?

[george]

So, head over to toyota in lunch to ask about a 76 deg thermostat. Intially they swear high and low that a kz-te only has one type of thermostat. A 82 deg one. So i tell them i took out a 76 deg one from my bakkie when i replaced it. They go silent... So we have a look on the computer. A 2000 model Kz-te only has one type of thermostat listed. I tell them it is a NTC branded thermo and must have come from toyota themselves.

Brainwave, see if the 2004 model kz-te also has only one type of thermo...

It has two

But unfortunately the temp is not listed on this other type. Its also a bit more expensive. The other option on the 2004 model has the same part number as 82 deg one. So by logical deduction we decide to order this mystery thermostat to see what temp it is.

Should receive it by Monday.

Now the question is... did the 2004 kz-te come with this mystery thermostat fitted? is it a 76 deg one? Could this explain why the 2004 kz-te motors have lower head failure rates...?

I like thanks Johan.Please sent me that part number once you get it I would also suggest to test it in water to see at what temps it open.How much was it

[JohanW]

Toyota received the thermostat this morning. Hats off to them getting it this quickly.

Upon inspection i found that it was not a 76 deg thermostat but a 71 deg one. So i still don't know where the 76 deg one comes from. But anyhow, it seems that all the 2004 Kz-te models came fitted with this one.

I will install this thermostat and report back on how long it takes for the vehicle to get up to temperature. Also how it is running when you really push it.

Anyone know of a good temperature gauge/system i can install to monitor the coolant temp? Madman? Alternatives.

The part number of this thermostat is: 90916-03121
Price R317, got some discount thou...

[george]

Thanks a mil Johan.Can you take some pics when you install it.I had a look at the weekend and it looks quite difficult to get in there

[Hoppy]

Die temperatuur wat op die termostaat gestamp is, dui die temp aan waarop hy heeltemal oop is, as hy oop is, is hy oop, dit kan hom nie kouer laat loop as hy hard werk nie, dit sal slegs die water gouer laat sirkuleer en dus koeler laat loop as hy nie werk nie.

[JohanW]

Hoppy ek stem saam dat as 'n termostaat oop is, is hy oop. Die probleem wat ek het met die feit dat hy eers op 82 volledig oop maak is dat die termostaat op die koudste plek op die blok sit. Dus is die temp by silinder no 4 baie hoër as 82. Dalk al 90 plus. Dus sal die gemiddelde temp oor die hele silinder kop ook hoër wees met 'n 82 as met 'n 71 of 76 aangesien die termo progressief is en kleiner toemaak as hy onder 82 is. Hierop maak ek my stelling dat die engin kouer behoort te loop met 'n laer temp termo. Op 'n baie warm dag en engin onder stres sal die 82 en 71 dieselfde vloei en werking hê. Maar sodra die stress vermider sal die 71 die temperatuur vinniger laat verlaag en 'n laer aanvanklike temperatuur handhaaf.

[Hoppy]

Ek twyfel of die temperatuur so baie verskil, die water vloei is te vinnig, die kouer termostaat sal wel n verskil maak as die bakkie nie hard werk nie, maar as hy hard werk sal daar nie n verskil wees nie. Onthou ook dat die enjin beter loop en ligter op brandstof is hoe warmer hy is, so die wen resep is om hom so naby aan 100 grade te hou as moontlik, maar dan genoeg verkoelingskapasiteit te he om te keer dat hy nie oor gaan nie, dis daar waar die verkoeler en "visco" hulle werk moet doen, die termostaat is lankal heel oop en uit die "equation"

[george]

Ek gaan gou iets quote wat die ander perd gese het.Jammer ek is so dom met die goed.Soos hy beskryf lyk dit of die thermostat nie oopbly nie

However, I carried out an experiment.

I heated the standard stat up in a pan of water and it gradually opened. I ran the hot tap in the kitchen until I couldn’t put my hand in it, then transferred the open stat to the hot tap water – It shut fast in under 3 seconds.
I then put the stat back into the almost boiling pan and it took a long time to open. I repeated the swap and it shut very quickly.

Now, the ‘stat lives in the block with the business end on the inside of the motor. As the motor heats up it will presumably get to the point where it opens and is immediately flooded with cold water from the bottom of the radiator. It seems it will then close very quickly.

Repeat the process – long(ish) time to open followed by a quick shut-off.

I think its very unlikely that the bottom of the radiator will ever get to the temperature where the thermostat stays open (unless you’re stuck in traffic in the Sahara), meaning that the motor is being fed small gulps of cool water.
That is probably OK if the car is running light – but towing a couple of horses over the Pentland Hills??? No wonder the motor gets hot and objects. Its working hard but there is sufficient airflow to keep the radiator cool, so the thermostat stays predominantly shut.
I can see why the motor may get so hot in places that the head is strained – and cracks.
Or does the ‘stat reach a steady state where it balances the heat in the block with the cool water from the radiator ? I don’t know, but I’ll bet it doesn’t open fully very often.

This is not a problem where the ‘stat is at the top of the motor as, when it opens, it is bathed in hot water and so stays open until the whole motor cools down to below its opening temp.

I looked on various websites and all quote the standard ‘stat for this motor as being 82 deg. However, Land Rover Defenders have 88 deg stats, with 74 deg versions as an option.
The Max Ellery manual for the 1KZ-TE states that the standard ‘stat is 74 degrees!
I enquired of Toyota and a 76 deg ‘stat is available – so I’ve fitted one:

[Hoppy]

It is not as simple as he discribes.
Fitting the t-stat in the bottom pipe is an idea started by the Germans in the 1970's in VW golfs, BMW's, merc's etc. The main reason behind this was to split the cooling system and have auxiliary flow that feeds the cylinder head and interior heater system continiously, even if the thermostat is closed. This auxiliary flow continiously suplies water to the interior radiator so that your heater works much faster, it runs through the cylinder head (that generates 90% of the heat) and heats up the back of the thermostat that has a second flap at the back that regulates the auxiliary system. The reason that the thermostat reacts slow is exactly to prevent heat surge and doesn't cause it.
The 1KZ motor was the first generation High-power Turbo Diesels Toyota produced, and there is some design mistakes in the cylinder head that shows after about 200 000km (cracks in the combustion chambers) this was solved with the redesigned 1KD engine, it is not a water-flow problem.
Hope this clears up some mis-understandings

[george]

It is not as simple as he discribes.
Fitting the t-stat in the bottom pipe is an idea started by the Germans in the 1970's in VW golfs, BMW's, merc's etc. The main reason behind this was to split the cooling system and have auxiliary flow that feeds the cylinder head and interior heater system continiously, even if the thermostat is closed. This auxiliary flow continiously suplies water to the interior radiator so that your heater works much faster, it runs through the cylinder head (that generates 90% of the heat) and heats up the back of the thermostat that has a second flap at the back that regulates the auxiliary system. The reason that the thermostat reacts slow is exactly to prevent heat surge and doesn't cause it.
The 1KZ motor was the first generation High-power Turbo Diesels Toyota produced, and there is some design mistakes in the cylinder head that shows after about 200 000km (cracks in the combustion chambers) this was solved with the redesigned 1KD engine, it is not a water-flow problem.
Hope this clears up some mis-understandings

Ah dankie Alan.