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Cooling mods for 1998 Prado Turbo Diesel 3.0 1KZ-TE


New Member
Jul 23, 2023
Country Flag

I made a post in a thread about this subject that has had no replies for 3 years. As I expected, I did not get anything for replies. So I have created a new post in the hopes I get a response.

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 something else I have noticed so far:
I go through nearly liter of oil over about 1200-1500km, 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?

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? Or is a 3" dump rather easily adapted to the stock exhaust?

Am I missing anything?

I am also intending to delete the EGR and give the manifold and throttle-body a good cleanse.

Thanks to all who have some insight!
For some reason or another engines burn oil from day one and engines like what could be described as a comfort zone where you top your oil up to spot on the full mark go for a thousand miles drive and its used a litre of oil so you top it up and do the same thing again and again and again and keep using oil now leave the oil level where it is and do your daily routine check of fluids after a while you should see the oil level will stay steady in its comfort zone if the level drops drastically then you know you have a problem found this out when I was a truck driver doing two thousand km a week the mechanic just told me leave it see what happens and keep some oil with you
When I got my automatic 97 Colorado the first thing I did was replace the radiator, thermostat, water pump, viscous hub and hoses with new genuine Toyota parts as preventative maintenance. I’ve also replaced the top and bottom ball joints with genuine Toyota parts.
A few years ago, while on a trip in the Pyrenees mountains, we almost cracked the head due to overheating (the ambient temperatures at the time were 42°C/107°F). Fortunately, I managed to get home to the UK intact. After poking around in the engine bay a bit, I removed the original viscous fan and opened it up to find that it was almost bone dry. I replaced the fan with a new one and replaced the 82° thermostat with the 76° one. That was about 2 years or so back. Anyway, we are off to the Italian Alps in a few days, and I couldn’t help but become a little paranoid over the new fan, so at the weekend I removed it and opened it up as I had read that many people have said that even when new, the fans were underfilled. While it did have some oil in it, I decided just to add some more and put another bottle’s worth in, though I kind of wish I had two bottles because it could definitely use more. At the same time as I had the radiator cowl off, I decided to back spray the radiator out to ensure the vents were as clear as possible. If we make it there and back without overheating again, I will call it a success and will be greatly relieved. For me, this will be a ‘getting back on the horse’ kind of moment and hopefully restore my confidence!
It's not supposed to be 'full' by design, it is a measured (cc) amount of correct weight/viscosity oil - oil of the correct type is used in r/c models which is often easier and cheaper to source.
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It's not supposed to be 'full' by design, it is a measured (cc) amount of correct weight/viscosity oil - oil of the correct type is used in r/c models which is often easier and cheaper to source.
There was no fear of it being anywhere near full Tractionman, there wasn't much to start with. At least it now has one bottles worth of the correct fluid in there. Hopefully, it will help.
I have a 3.4 petrol so different engine but one of the first additions I did when I base-lined the truck was adding a coolant temp gauge on the top rad tube, really quick to install and you have constant real undampened reading of your coolant temp. it also gives me the peace of mind of knowing the thermostat is working well. the 5vzfe seems to run a top temp of 91C, highest I've seen is 92C when worked hard.
tangentially as my transmission has failed and it's in for a rebuild (going in later this week) I am adding an ATF temp gauge too and an external atf cooler too...