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Cooling the 1KZ-TE motor:

I use a specific thermo switch---from memory it came from a Fourtrak---that opens at 100deg.C and closes at 95deg.C

Some years ago I worked for the Rover co. on engine testing. We would regularly carry out a "Butch" test on a new engine. The engine was set up on the rig, started up and then set at full load, 6,000 rpm. The water temp. under the stat, was raised, and held, at 110deg.C and the oil, in the sump, raised and held at 130 deg.C. The oil was a standard petroleum based 20-50. The test lasted 30 minutes, after which the engine was switched off, removed to the bench, stripped and checked for damage. The oil was tested in the lab for any contamination. The engine was then re-assembled with new shell bearings and gaskets and put back onto the test rig. The engine was then subjected to the standard running in schedule---10 hours, varying loads, varying speeds---before the standard 10 hour running schedule. We would continue this schedule until we got bored. At intervals we would carry out full power runs, blow by tests and economy checks. These tests showed that there was no measurable, consistent, difference between an engine tested in this way and an engine treated normally.

Back to my 1KZ-T engine.

With the set-up described, the only times the fan comes on is during hard "off-road" work. Steep climbs or heavy mud. The only time the gauge has registered close to the red was climbing Walna Scar, West to East, when the relay failed on the fan circuit. I stopped at the top, allowed the engine to cool and then changed the relay. If you find yourself in this situation, DON'T TURN THE ENGINE OFF, just let it run, it will only take a few minutes to cool down. If you turn the engine off, the flow of water ceases, and heat soak will create variable temp. in the head and block which can cause warping and head gasket problems.

Roger
 
A further point.

The KZJ-70 is more of a utilitarian vehicle than the Colorado. It has been described as a "Thinking Man's 90". It has 4 minor gauges, fuel, volts, oil pressure and water temp. Maybe Toyota have fitted more accurate gauges, bearing in mind the nature of the motor.

Roger
 
as this is the most in depth discussion i have come across regarding KZ's cracking there heads i will add my findings here

this is a pic of the thermostat housing. purple arrow is heater return, red arrow feed from head/bypass and green feed to water pump inlet

as can be seen there is a casting to keep the hot water from the head around the bulb of the thermostat

1-1.jpg


pic to clarify the feed from thermostat (blue arrow), then into block gallery/oil cooler (red arrow)

2-1.jpg


from the oil cooler gallery it crosses to the exhaust/rhs of the block as in bob's first post picture

BobMurphy said:
I have marked-up a picture of the block to illustrate my perception of the coolant flow:
DSCN5852copy.jpg

and this is the flow through the head

3-1.jpg


blue crosses are blocked water ways in headgasket, small red arrows are the vent holes from oil cooler gallery up behind the combustion chambers

the red lower arrows is the bulk of water flow up into the head. increasingly larger holes towards the rear of the block

pink arrows are flow through head towards the thermostat/bypass feed and top hose

yellow arrows are drilled water ways between the valves as can be seen in this pic below

4.jpg


other half

5.jpg


this is a early head from a 4runner, so i'd be interested to see what differences there are with a later head ?
 
That's very interesting. I have been working from an engine thats in service so haven't chopped anything up for a peek inside.

The cut-away head is revealing - thanks for showing us that.

Which begs the question (and a whole new thread) . . . . How on earth are the heads cast :? :?: :?:

Surely they can't used sand-resin formers that have to be knocked out :think: .

One for another time I guess.

I think the key to these motors is the temp gradient between the top of the head and bottom of the block, and the time it takes for the thermostat to react.

Data from the top-mounted thermostat & temp gauge will hopefully reveal what's going on.

Keep the info coming :thumbup: :thumbup:

Bob.
 
very informative thread, thanks for posting these pics up and the explanations
:clap:
 
great info. :thumbup:
i've got mostof the bits to play with mine, but i'm off to phuket at the end of next week, so i wont start stripping the surf down until i am home again (need the surf for a ~1440km trip to the city and back). so it's still going to be a while before i can post my findings with a top mounted thermastat.
 
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i've got a massive update on where i am with my thermostat relocation, but the forum wont let me post it as i dont have 15 posts. so all my pics wont work. ? :(
 
I think you will just have to get more involved, and answer a few other question, and ask a few questions, until you have enough posts.

Gra.
 
What was the news?

i've got a massive update on where i am with my thermostat relocation, but the forum wont let me post it as i dont have 15 posts. so all my pics wont work. ? :(

John,

did you ever post the info?
I'm really interested to know what you've found out. Even if you cant post the pics, can you tell us?

I'm now on surf number 3 having lost 2 to ruined heads, both because of towing , when previously the vehicles have been good and strong. I've got more towing to do soon and don't want to wreck vehicle number 3.

I'm considering either a transmission oil cooler, or a lower temp stat. But relocating a stat to the top of the rad makes the most sense and removing the original, or at least removing the centre core completely.

In essence did your experiment work?

Thanks for any info you can offer.
 
John,

did you ever post the info?
I'm really interested to know what you've found out. Even if you cant post the pics, can you tell us?

I'm now on surf number 3 having lost 2 to ruined heads, both because of towing , when previously the vehicles have been good and strong. I've got more towing to do soon and don't want to wreck vehicle number 3.

I'm considering either a transmission oil cooler, or a lower temp stat. But relocating a stat to the top of the rad makes the most sense and removing the original, or at least removing the centre core completely.

In essence did your experiment work?

Thanks for any info you can offer.

Your first move probably should be to get a dedicated oil cooler and make sure the clutch in your fan is in tip top shape. Whilst your at it you should also fit a proper temp gauge ... as the Toyota ones are not so accurate.
 
Thank you

Your first move probably should be to get a dedicated oil cooler and make sure the clutch in your fan is in tip top shape. Whilst your at it you should also fit a proper temp gauge ... as the Toyota ones are not so accurate.

Hi Grant.

Thanks for the advice.
Can you recommend an oil cooler? Has anyone used fan cooled oil coolers, or just plain radiator style?
I was thinking of ditching the viscous fan, in favour of an electric, or twin fans. The forums I've read seem to indicate lots of problems with the clutches.

It's a real shame the 1kzte engine suffers from this Achilles heal, because otherwise it's a great engine.
 
Just top up the oil in the viscous fan. Mine is on all the time now and I don't seem to pay a fuel penalty.
 
Does anyone have the Toyota part number for the viscous oil please?

I want to change the oil in my fan before I refit it. :icon-biggrin:
 
I just used silicone oil for model car lsd diffs. Its the same stuff, but you need the correct cst weight for the fluid and that i cant remember tight now

Sent from my GT-P1010 using Tapatalk 2
 
Your first move probably should be ...

... to fit a quality EGT gauge and learn to drive with a lighter foot on some regimes of driving.

Yes, I know you will say that you already drive feather-footed, but the same I was thinking of my driving and many of my friends also thought the same about themselves. For all of us it was quite a revelation to start driving "by the EGT info". It didn't mean we started driving slowly, just ... differently. And no cracked heads after that (of course we sorted the cooling system first, but nothing above the factory specs and installations).
 
Does anyone have the Toyota part number for the viscous oil please?

I want to change the oil in my fan before I refit it. :icon-biggrin:

Hi Ben,

there seems to be a good discussion on oil weights on the hiluxsurf . co . uk forum, sorry can't post the link until I have 15 posts.
search - viscous fan oil replacement

6,000 seems standard, but 10,000 seems to be suggested for earlier operation - 30ml


Thanks again guys for all the advice.
 
Quick update found this -

The manual says to use 50mL of 3000Cst. silicone fluid to refill the fan clutch.
Each bottle is 18mL. Toyota P/N 08816-03001
 
John,
.......But relocating a stat to the top of the rad makes the most sense and removing the original, or at least removing the centre core completely..........

i think removing the thermostat or core would make the cooling worse because the thermostat restricts the flow of hot water from the head through the block into the back of the thermostat housing, without it there would be a constant stream of hot water into the cold coolant coming into the engine from the rad. :think:

a better temp gauge is essential, the OE one is not fit for purpose. an EGT gauge is also very usefull for indicating what 'load' is on the engine and heat it's producing before the water temp gauge will even move :thumbup:

here's where i fitted my gauges, drilled and tapped the outlet for an adapter to fit the sensor, small digital gauge from ebay, egt gauge sensor in manifold pre-turbo, Auberins gauge in dash (not in a LC90 but i added the gauge pics just for referance)
DSCF2247_zps0bf54c5b.jpgDSCF2252_zps82a3c802.jpgegt_manifold.jpgegt_dash.jpg

also fitted a 76 deg.C thermostat, which keeps the peak water temps under 105 deg.C, no idea how hot it used to get with the 82 deg.c but over 110 probably :icon-confused: so the question's how hot's too hot ? considering that's an average of the water coming out of the head, so there's probably hotter spots in the head ?

but i reckon the 76 deg.c temp is too low when just pottering around, so my next experiment will be when i go to a rear mounted rad, i will remove the thermostat and plug the hole thats feeds the rear of the thermostat (will include a small bleed hole to maintain a small level of flow, to remove air etc ?) and then utilise an electric water pump with the flow controlled by water temp so i can have a higher 'low load' running temp, and still be able to keep the temp under control when under 'high load' situations. will need a good setup when i get my big turbo and 25psi boost :icon-twisted:

would be interesting to see some info from a top mounted thermostat set up though :think:
 
For the EGT sensor did you just drill and tap the manifold?

Was it difficult to do? :icon-smile:
 
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