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KZJ 73 Overheating Issues

loco_ola

Active Member
Joined
Oct 25, 2017
Messages
56
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france
Hello everyone hope you can assist with a continuing saga I'm having with my LC.

I bought a kzj 73 last year and have had continual overheating issues with sustained periods of uphill or speeds over 70. I noticed mainly it was happening at over 3k rpm. Temperature would suddenly rise, and coolant would leak out the expansion tank.

Having changed the thermostat and cleaning and reverse flushing the rad I moved onto the head.

I've just taken it apart and was surprised to see the head looks pretty new.

The old owner has been a dead loss with anything and obviously just wanted this problem off their hands.

I wonder if any of your experienced guys could offer any guidance or suggestions? Water in the turbo or something?

I'm yet to check the head for warping as I have no straight rule here.

Here's some photos. Any suggestions or advice would be greatly appreciated.

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It took me a long while to work out why my truck would only overheat at high speed but it turned out to be the fan shroud was lose and catching the fan adding a ridiculous load on the engine with only a feathers touch .

Trust me to suffer a problem nobody else might even suggest i check so there you go .
 
I've just tried 45ml of 10000cst in my viscous and its too much, fans engaged all the time, drained out a bit to 30ml and it still engages to much. Once I've done my LCA bushes I'll have another go at the fan
 
I wonder if a good quality electric fan and thermostat would help with this issue?
 
Don't forget to check the rad cap isn't seized and not venting, I had exactly that with the same symptoms. Changed the cap for a new one and all was well, check the cheap and easy stuff first.
 
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Thanks for all the replies guys.

Man I should posted here before I tore it all apart.

Now the question to get the head pressure tested or not before putting it all back together...

I took the viscous coupling off but all bolts are soft and totally locked in place. I'll have to drill it if I want to get in... Or I guess buy a new one. Annoying as it's out now.
 
I'll give that a try tomorrow. it's strong enough for that kind of abuse?
 
If it works you don't have to drill :D some of my screws got damaged and the impact driver got them out
 
Get it pressure tested. I'm sure it won't cost a lot and can save you potential hassle if it does have any cracks that aren't visible...plus peace of mind
 
Impact driver worked a treat, even with the mashed screw. Will definitely be replacing them with bolts.

Trying to find a pressure tester here in the Alps is proving to be a pain. Actually finding most things here other than mountains is tricky.
 
One thing that's just crossed my mind. It was putting out black smoke at high revs.... Is it possible the injectors need sorting and that's causing overheating?
 
I've just tried 45ml of 10000cst in my viscous and its too much, fans engaged all the time, drained out a bit to 30ml and it still engages to much. Once I've done my LCA bushes I'll have another go at the fan

I read somewhere that 7000/8000 is the way to go for the 80 series at least. Sure I read the same about the kzj 70s...

Check this thread.
 
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I'd read that and also the thread on IH8Mud, seems Toyota used a variety of viscousity's, 3000cst in the US and 10000 in Oz. I decided on 10000cst as I use mine a lot in temps of 30-40C ambient.

Might have to drop to 7000cst and see how I get on
 
Thinking about it, I can't see it's the fan coupling because it still happens at high speeds... The fan would be having little effect.
 
I put 10000cst in mine. definitely fan engages more. the clutch temperature adjusting screws are very soft too, damaged one attempting to open with a normal screwdriver.

My engine egt dropped a lot(70-100deg post loader) after having injection pump and injectors serviced. also, theres a bit more power and fuel economy improved by .5l/100km.
 
Head test has come back good.... Back to the drawing board arrrrrrrgh.

Thermostat I guess I can simply test by taking it out and then a trip up the mountain but it's a new one, cap tested good too. Fan I will replace oil - but I don't think it's that because of the high speed problem.

Injectors have been confirmed ok and recently done. Seems the person before me had all the same issues and couldn't find the answer.

So too much fuel hence the black smoke if not injectors? Or maybe something to do with the turbo? I don't have much turbo experience.
 
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