Toyota cooling sytem tune up.

[Smurf]

I have just done some work to my cooling system in my Prado, partly due to the engine majorly overheating a weekend or two ago on a steep uphill climb, not offroad, just a long slow climb up a dirt road.
Temperature dropped quickly once the heater was turned on and the fan cranked. No apparent damage has been done but time will tell.
I am getting a brand new radiator built next week as I was unable to locate a new replacement unit.
The new radiator will have a bigger core and possibly have the trans cooler removed and an external cooler fitted, as most toyota auto radiators have the outlet pipe partially blocked by the trans cooler.
Another option here is to move the outlet pipe to one side so the trans cooler isn't blocking it.
So I started looking into other ways to improve the cooling in the 2L-TE engine.
There are several simple things that can be done to help the cooling system, ranging from lower temperature thermostats to hi flow units, to re oiling the viscous fan hub and adjusting the operating temperaure of the hub, through to swapping in a different fan. And the removal of the in radiator trans cooler.

Thermostat,
I found an 82 degree Toyota thermostat that supposedly has a larger opening to the standard thermostat. Part number 90916-03079.
But Tweake mentioned in another thread that Toyota thermostats only start opening at their rated temperatures, so I tested this.
My old 88 degree thermostat stared opening at 93 degrees,
The new Toyota 82 degree thermostat started opening at 86 degrees.
Tweake also mentioned that Tridon offered an 82 degree hi flow thermostat so I also ordered one of these to compare. The packaging claims 30 % extra cooling flow.
When tested it was nearly fully open at 83 degrees.
So I have fitted the Tridon hi flow thermostat along with a new Toyota radiator cap.

Viscous fan.
I removed my fan hub intending to replace the silicone oil and reset the opening/operating temperature of the hub.
Once removed from the Prado and cleaned up I realised that the temperature sensing Bi-Metal spring on the front of the hub was broken. well that explained my overheating issue (Hopefully).
Fan refitted temporarily til a replacement was found.
Went to the wreckers and grabbed another fan hub and also tracked down a 10 blade fan from 5LE, I found this in a 2001 2WD Non turbo Hilux.
These are reputed to move a lot more air than the 7 bladed fan fitted to the Prado and most Surfs. There is also an 8 blade fan from the 2H and 3H engines that is a good replacement.
The 10 blade fan is also thinner so sits further away from the radiator.
Fan was a straight swap.
Info found in this thread here...
http://www.toyotasurf.asn.au/forum/view ... hp?t=12042

I initially grabbed a syringe of silicone oil from BNT to re wax the hub. But after a bit more reading I found out that Toyota use three different grades, 3000cST, 6000cST, and 10000cST. cST = centistoke which is basically a measurement of viscosity.
So Toyota wanted $50 for an 18ml pipette, versus BNT $20 for 50ml.
Fan hub requires 50ml from empty.
With the BNT stuff not having a viscosity rating on it and me thinking more viscosity means more resistance in the fan hub means more drive to the fan, I went to a local hobby shop and bought a 50ml bottle of 10000cST silicone diff gear oil, which is used in diffs etc of radio controlled cars. exactly the same fluid as used in the viscous fan hubs. Cost, $15.
So hub opened and left to drain for a few days til I had time to swap everything over.
The old oil in the hub was a dull dark golden syrup colour and thickness, both new lots of oil were clear, the new toyota oil new seems to be a gold/yellow colour too.
Hub refilled and adjusted according to info from these two web pages.
http://www.offroad80s.com/how-to-top-up ... t1160.html
better link with working pictures http://forum.ih8mud.com/80-series-tech/ ... h-mod.html
http://neuralfibre.com/paul/4wd/tuning- ... fan-clutch

My fan hub is the same as in the second link.
I haven't test driven yet, but at idle after the thermostat had opened my temp gauge is sitting approx one needle thickness lower than it used to,(scientifical I know) there is also a lot more air being pushed out by the fan at idle once at operating temperature.

[andrew007]

very interesting,cheers mate.i think i will do the same

[kbushnz]

Great write up. I await your results....

[tweake]

nice to see some good testing done on the thermostats.

i would get an aftermarket temp gauge and fit the sender in where the factory one is.
you may find the big fan sucks a bit more power from the engine which could be a pain with such low powered engines. you may have to much cooling.

see how hot the heater runs, i suspect it will be very cool.

[Smurf]

nice to see some good testing done on the thermostats.

i would get an aftermarket temp gauge and fit the sender in where the factory one is.
you may find the big fan sucks a bit more power from the engine which could be a pain with such low powered engines. you may have to much cooling.

see how hot the heater runs, i suspect it will be very cool.

Tweake, I am almost expecting it to run too cool, but it is easy to swap the 7 blade fan back in if need be or set the viscous to come on a bit later.
I will be fitting a temp gauge soon to get a temp reading.
The thermostat temps were suprising, esp the old unit that was removed.

Low power engine?? No power engine. LOL

[tweake]

i expect it to sit hard on 82c due to the thermostat. which is why i swapped it out for the 88c version on mine.

[IcedJohnno]

Great technical writeup Smurf. Exactly what I come on here for.

Was the oil sold rated in Cst, or whatever the equivalent is in SAE ratings?
Does any of your research state what the Cst rating is meant to be for the Prado fan hubs as fitted to the 1KZ?

Have you changed your coolant to the Toyota antifreeze?
Or added RedLine Water Wetter?

I am about to change both of mine again.

Will look into my fan hub and thermostat too. The latter is exactly the same as Toyo designed it to be, though I have replaced it when I got a new top tank fitted and the radiator rodded out 100,0000 km's ago when the head went.

[oldblue]

A while back, I added extra oil to the Viscos and found that it was locked up at a lower RPM.

[Smurf]

Great technical writeup Smurf. Exactly what I come on here for.

Was the oil sold rated in Cst, or whatever the equivalent is in SAE ratings?
Does any of your research state what the Cst rating is meant to be for the Prado fan hubs as fitted to the 1KZ?

Have you changed your coolant to the Toyota antifreeze?
Or added RedLine Water Wetter?

I am about to change both of mine again.

Will look into my fan hub and thermostat too. The latter is exactly the same as Toyo designed it to be, though I have replaced it when I got a new top tank fitted and the radiator rodded out 100,0000 km's ago when the head went.

John,
the oil sold was rated in cST, the BNT oil had no rating on it, and they couldn't tell me its rating either.
Only reference I have found so far stated that the 10000 cST oil was for the Toyota SUVs, but this was contradicted in a seperate thread, where someone stated their manual specified 3000 cSt for the fan hub. I haven't come across anything specific to the 1kz other than the differences in thermostats between 1KZ, and the L series engines.
I cannot find the threads at present but if I do I will post them up.

[likemagic]

John,
the oil sold was rated in cST, the BNT oil had no rating on it, and they couldn't tell me its rating either.
Only reference I have found so far stated that the 10000 cST oil was for the Toyota SUVs, but this was contradicted in a seperate thread, where someone stated their manual specified 3000 cSt for the fan hub. I haven't come across anything specific to the 1kz other than the differences in thermostats between 1KZ, and the L series engines.
I cannot find the threads at present but if I do I will post them up.

the different cst oils are dependant on the market, the hot climates use 10000, while cooler climates use the thinner oil. As most of the Surfs and Prados are imports they have the thinner oil for Japan, where the Ozy ones had the thick oil.
Maurice

[Smurf]

John,
the oil sold was rated in cST, the BNT oil had no rating on it, and they couldn't tell me its rating either.
Only reference I have found so far stated that the 10000 cST oil was for the Toyota SUVs, but this was contradicted in a seperate thread, where someone stated their manual specified 3000 cSt for the fan hub. I haven't come across anything specific to the 1kz other than the differences in thermostats between 1KZ, and the L series engines.
I cannot find the threads at present but if I do I will post them up.

the different cst oils are dependant on the market, the hot climates use 10000, while cooler climates use the thinner oil. As most of the Surfs and Prados are imports they have the thinner oil for Japan, where the Ozy ones had the thick oil.
Maurice

I'd agree with this, several threads i read led me to the same conclusion.

[Smurf]

After a half hour drive and giving the engine a good work out, heavy acceleration, hills etc.
My temperature gauge sat steadily at least one needle thickness lower than it used to at normal operating temperature.
Once I got home I put the thermometer into an air vent in the dash and ran the fan. Got an air temperature of 70 degrees. Not that it proves anything but it was still too hot to hold your hand directly in front of the vent, It was cooler definitely cooler than it was prior to the changes.
Once hot and sitting at idle there was a masssive increase in air movement from the fan compared to what I was getting prior, What was most noticable was with my hand in front of the radiator I could feel the air being pulled past my hand and through the radiator. And the fan was clearly audible at operating temp.

The next step is a decent temp gauge and I am trying to find out if it is possible to mod the factory temperature gauge the way the Surf and 80 series gauges can be to remove the dead spot. There are no resistors etc on the back of the dash temperature gauge, so I am wondering if if the dead spot issue with the Surfs etc isn't applicable in the Prado?
Either way an aftermarket gauge is being fitted

[tweake]

i wouldn't bother tweaking the factory gauge. just bin it and run aftermarket.
i fitted aftermarket gauge with sender in the aircon senders place. however i now never look at factory gauge so i could have fitted it in place of the factory one.

[Smurf]

Brand new radiator fitted and a SAAS aftermarket temp gauge now fitted into the top radiator hose.

I couldn't find a replacement top hose so I had a rummage through the hoses at Repco and found a Mitsi L300 van top hose is almost identical, so grabbed one to cut in half to fit the temp sender.


In the radiator the transcooler does not block the bottom outlet pipe so I left it in and will hook up the external transcooler to run inline.

I have run it for a week and the temp now sits right on 80-82 degrees.
The factory gauge starts moving first due to the aftermarket one being fitted after the thermostat.


I have done a bit of towing and have tried to load up the engine and the temp doesn't move. But this has all been on the open road on flat ground so not much of a test.
I was hoping to give it a good run back up the hill it overheated on a few weeks back but a slip has closed that road, so I will be running it up a few hills tomorrow if it is fine to see if I can get the temp to move.

[SMOKEY]

Hi Keith, great write up. Have you fitted a Pyro gauge (exhaust) and if so what readings are you getting ?. If not I think with one fitted your driving style will change and this will bring your temps down, in my experience with the 2LTE and the 1KZTE this was the case, good luck . In saying that my son Maurice thrashes his Surf as is holds 100kph all the way up Skippers and after fitting new radiator has no overheating troubles.

KEEP COOL,

FITZY.

[Smurf]

Hi Keith, great write up. Have you fitted a Pyro gauge (exhaust) and if so what readings are you getting ?. If not I think with one fitted your driving style will change and this will bring your temps down, in my experience with the 2LTE and the 1KZTE this was the case, good luck . In saying that my son Maurice thrashes his Surf as is holds 100kph all the way up Skippers and after fitting new radiator has no overheating troubles.

KEEP COOL,

FITZY.

Pyro is the next job. I don't usually push the engine intentionally, mostly due to reading about the exhaust temp readings I have read about on here and other sites.

[praduck]

Ideal I will be doing this to mine now

[Smurf]

10 months later and the thermostat is toast. Starts opening at 90-92 degrees, not fully open until nearly 100. This may account for my warmer running recently. Temp. was fine on the flats (82-85 degrees) but any reasonable length gentle up hill incline it started getting warm really quick.
I couldn't get a replacement for the 82 degree hi flow unit so had to throw a standard 82 degree one in for now.
I also fitted a new water pump today, I used a 3L/5L Toyota one as the blades are bigger than the 2LT ones, and are meant to move more water. The old pump was only 2-3 years old and had nothing wrong with it.
With the new pump it definitely took longer to get to temp with it sitting at idle from cold, even with a more standard thermostat in it.
Oil pressure is still poo (shame a water pump didn't improve this) so a rebuild/new motor is still on the cards soon.
Rebuilt injectors today as well, thanks to Injector Rod for sorting me out.