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Cooling the 1KZ-TE motor:

Ben said:
My overheating issue are finally sorted! Fitting an electric fan caused nothing but problems, reverting back to the viscous fan has fixed it! :icon-rolleyes:
Click to expand...

Exactly the same problems I had with my 80, viscous fan back in, end of problem. :dance:
 
Looks like Toyota knew what they were doing
 
froggy Steve said:
Hi Ben, just ordered one but noticed that is just has a 'non screw in' sensor - how did you fit yours? Was is easy or can a thickie do it :)
Steve
Click to expand...

I used a crimp on terminal and put the sensor into the crimp on terminal and crimped and heat shrunk it, then put some electrical tape around. The terminal was one of the ones with a 8mm hole so I could then put one of the rocker cover bolts through it. :thumbup:
 
Ah, so (Chinese new year), the sensor isnt in the coolant then?
Okelydokely
Cheers!

Sent from my GT-P5110 using Tapatalk
 
I have bolted my sensor to a thermostat stud seems to work very well so far
 
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mine seems to run at 72c at motorway speeds and around 78c in traffic
 
1KZ-TE cooling

Just seen this really interesting thread and hope I can add some intel and ask for some in return.
I've got a '96 Surf with the 1KZ-TE motor. Cracking vehicle, used for everything from heavy towing to continental touring. 240k kms on the clock and going like a swiss watch. Never uses any coolant. Only ever had two problems with it (well the same problem, twice) - Overheating, fully laden on fast, long motorway inclines. Only happenned twice but both times the same, fully loaded, long hill, pedal hard down as usual (!) 80-85 mph, sudden but partial loss of power, look down - temp gauge is in the red then a few seconds later swings back to below normal, power returns and we're off again.

I've fitted an aftermarket temp gauge (sender fitted in top hose) to see what's going on and the readings are interesting.
  1. In normal driving the temp never gets anywhere near 80'c suggesting the thermostat is closed and the engine is still managing to cool itself (cabin heater always good and hot so I don't think the stat is stuck open)
  2. In motorway driving the temps climb slowly up to 82 degrees then come straight back down to 50ish before climbing slowly back to 82, then crashing back to 50ish. This continues for the whole journey. Suggests the stat is opening, letting a slug of cold water from the rad into the engine and then closing again. Thermal cycling like this can't be good for the block and head. Interestingly the factory temp gauge never moves from horizontal, but the aftermarket gauge can be reading anywhere between 50-80'c!

I agree with the guys above - on a long incline the engine temp is climbing faster than the system can cope with and goes into overheat before the stat can open and keep it cool. Also totally agree the factory temp gauge is cr@p!

I'm planning a bit a cooling system overhaul as I really don't want a cracked head. I'm planning to flush the whole system, acid wash the rad, fit a 76'c 'stat and change the fluid in the viscous coupling, However I recon as others do that the 'stat in the bottom hose design is a bit flawed and will still lead to thermal cycling. I'm keen to look into fitting a stat in the top hose.

Two questions:-
  1. Has anyone else with an aftermarket temp gauge seen similar temp behaviour or have a just got a sticky stat?
  2. Can anyone who has fitted a top-hose thermostat provide any info on what parts they used, where they were sourced etc?
 
I dont do much towing with mine, just the occasional 1.5t / 1.75t trailer and mower / tractor when the van is in for a service, and luckily, to date, have had no sign of over heating, but I guess its too late once you do :(. When the after market temp gauge arrives I will fit it ASAP and watch like a hawk.....

Steve
 
Interesting post Jon. :thumbup:

I've not noticed my engine temp surging like yours but then my temp sensor isnt fitted in the coolant hose and is instead monitoring the engine temp via one of the bolts going down into the block, maybe thats why I havent noticed it. :think:

Steve, you could just as easily mount your temp sensor in the top rad hose if you wanted to monitor the actual coolant temp. Just undo the top hose clamp and push the sensor inside the hose and then do the clamp back up.

I've been quite happy with how mine is mounted but that is the other option. :icon-smile:
 
'Steve, you could just as easily mount your temp sensor in the top rad hose if you wanted to monitor the actual coolant temp. Just undo the top hose clamp and push the sensor inside the hose and then do the clamp back up'

I think I might try that to start with, as long as coolant wont pee out everywhere!
 
Hi Jon,

that info about pulsing temps seems to be what others are saying on other forums - such as hiluxsurf.co .uk.
I'm driving a 93 surf, 1kz-te and having broken 2 surfs already by overheating when towing and not noticing until too late, with this third one I didn't want a repeat. I ordered from jegs.com a meziere hi flow in line housing 680- WN0072 and hi flow thermostat 680-WN0070170 - 170 f or 77 c thermostat, they do others though - spliced in to the top hose. The housing simply screws together, but the jegs own make which bolts together looks good too.
Will repost when I've done a few more trips, but tomorrow going to fit a digital temp gauge, so should confirm if the alteration has worked. Thinking of popping this in just before the stat, so should measure head temp, and will tell me if the stat stops working too, or that's the plan.
Thanks for the info.
Ps took about a week to get from the states to me in the uk, pretty good.



Jon_Tallis said:
Just seen this really interesting thread and hope I can add some intel and ask for some in return.
I've got a '96 Surf with the 1KZ-TE motor. Cracking vehicle, used for everything from heavy towing to continental touring. 240k kms on the clock and going like a swiss watch. Never uses any coolant. Only ever had two problems with it (well the same problem, twice) - Overheating, fully laden on fast, long motorway inclines. Only happenned twice but both times the same, fully loaded, long hill, pedal hard down as usual (!) 80-85 mph, sudden but partial loss of power, look down - temp gauge is in the red then a few seconds later swings back to below normal, power returns and we're off again.

I've fitted an aftermarket temp gauge (sender fitted in top hose) to see what's going on and the readings are interesting.
  1. In normal driving the temp never gets anywhere near 80'c suggesting the thermostat is closed and the engine is still managing to cool itself (cabin heater always good and hot so I don't think the stat is stuck open)
  2. In motorway driving the temps climb slowly up to 82 degrees then come straight back down to 50ish before climbing slowly back to 82, then crashing back to 50ish. This continues for the whole journey. Suggests the stat is opening, letting a slug of cold water from the rad into the engine and then closing again. Thermal cycling like this can't be good for the block and head. Interestingly the factory temp gauge never moves from horizontal, but the aftermarket gauge can be reading anywhere between 50-80'c!

I agree with the guys above - on a long incline the engine temp is climbing faster than the system can cope with and goes into overheat before the stat can open and keep it cool. Also totally agree the factory temp gauge is cr@p!

I'm planning a bit a cooling system overhaul as I really don't want a cracked head. I'm planning to flush the whole system, acid wash the rad, fit a 76'c 'stat and change the fluid in the viscous coupling, However I recon as others do that the 'stat in the bottom hose design is a bit flawed and will still lead to thermal cycling. I'm keen to look into fitting a stat in the top hose.

Two questions:-
  1. Has anyone else with an aftermarket temp gauge seen similar temp behaviour or have a just got a sticky stat?
  2. Can anyone who has fitted a top-hose thermostat provide any info on what parts they used, where they were sourced etc?
Click to expand...
 
In addition to my D4D LC 90 ( fairly recent purchase) Ive had an intercooled KZN185 3rd gen Surf for 6 years. I fitted an aftermarket temp sender in the top hose hose using one of these. Radiator-Hose-Adapter-32mm-Water-Temp-Sensor-Alloy-Pipe-Connector-Joiner-Blue. ( Cant post link but available on a well known auction site and other outlets ) and I see the same fluctuations as John Tallis which Ive always thought weird and may only now (after reading this thread ) be starting to understand. Im not particularly worried about it. I have an auto, and have fitted an external ATF cooler ( bypassing the in rad one) also with a stat and temp sender. Ive also flushed the cooling system, fitted a new standard stat, a new rad cap and replaced the water pump,and the viscous fan oil, all just in the hope that I can keep my head intact and also to avoid the strawberry milk shape. I,ll be doing all the same things to the LC when the sun comes out again. The highest temp Ive seen on my aftermarket gauge is 103 while dragging a 1400 kg caravan up the Slocht summit on the A9 leaving Inverness on a warm summer day.. Normal towing of the same van its 80-83 and fairly steady. I only see the big temp drops when driving solo and steady. Regarding the ATF cooler in the rad, its better described as a heat exchanger as it also puts heat in to your ATF. On a normal Scottish day trundling along at 60-70 ( not towing) with the tranny in lock up, my ATF temp can be quite low 20-40 rather than the desired 80, but again its not a worry. Good thing is Ive never seen the ATF above 80 even on these uphill tows.
As many have said, the stock Toyota gauge has three positions, cold, normal, head gone. Someone somewhere on the Aussie Surf forum has a write up on doing things with resistors to make the stock gauge more responsive and a few Surf owners here have done this. Its always interesting to see other peoples views and plans, but for me keeping the cooling system in top condition is the way to go.
 
One more question?

On the two occasions that my truck has overheated I've only noticed because of a sudden but partial loss of power. Does anyone know if the ECU has a function that limits engine output at high coolant temps or is there something else going on?
 
Fan cooled ATF cooler?

Bogus said:
fitted an external ATF cooler ( bypassing the in rad one) also with a stat and temp sender.

Hi Bogus.
Did you fit a cooler with a fan, or just straight forward rad, no fan?

it sounds a cooler should be my next purchase to save the head.

Best wishes
Click to expand...
 
TimB said:
Bogus said:
fitted an external ATF cooler ( bypassing the in rad one) also with a stat and temp sender.

Hi Bogus.
Did you fit a cooler with a fan, or just straight forward rad, no fan?

it sounds a cooler should be my next purchase to save the head.

Best wishes
Click to expand...

Just a rad, no fan, mounted in front of the main rad.
Click to expand...
 
Jon_Tallis said:
Just seen this really interesting thread and hope I can add some intel and ask for some in return.


  1. Has anyone else with an aftermarket temp gauge seen similar temp behaviour or have a just got a sticky stat?
Click to expand...

no, sounds like the thermostat is knackered.

perhaps that is a contributing factor to cracked heads, old thermostats not reacting properly ?
 
Does anyone know the Toyota part no for a 76 degree 'stat or which vehicle they were fitted to as standard? My local dealer can't get one without this info. Alternatively where I can get an aftermarke one?
 
Jon_Tallis said:
Does anyone know the Toyota part no for a 76 degree 'stat or which vehicle they were fitted to as standard? My local dealer can't get one without this info. Alternatively where I can get an aftermarke one?
Click to expand...

Try this Jon, The genuine part number for the 76-90 degree thermostat is 90916-03119.
 
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