Ideas anyone...4.5 Mystery overheating - NOT the usual suspects

[zerolux]

Thanks for all the ideas guys, so here goes with some answers....

New Sensors fitted, havent tried the mechanical sensor yet, but its hot (boiling) when the factory gauge is almost on high, system has been bled to remove airlocks including angled for the trap at the back of the block, it does have a recovery system with a new radiator recovery cap fitted and recovery system has been working fine. after the last overheat, i replaced the radiator with a 3 core 60mm alloy one, but that doesnt seem to of been the problem....separate tranny oil cooler as well as bottom of the radiator, but tranny temp light works but has never lit up..

So you've got me thinking about an oil blockage, oil is changed regular between 5000 and 8000, so i'll flush that tomorrow just to be sure, but as intermittent as it is it could be weeks before it happens again...thats whats making it hard to pinpoint, and after it overheated, refilled water and it was right, drove it home and didnt get above just below half....

Has anyone had issues with fuel and choke plate maybe sticking and leaning out the mix, or ecu issues that lean out the fuel causing overheating...just brainstorming in case the restart of the car reset the issue..got me totally buggered (I apologise for using a Toyota term here )

[threedogs]

Is the water pump spinning like is it tight and impellor not slipping.???

[nissannewby]

Yeah its quite possible it could be.

[zerolux]

Waterpump is new and tight...

Nissannewby..which possible you thinkin?? fuel mix??

[nissannewby]

Nuh the air lock my phone was slow to load everything so disregard that post lol. Is there any wear in your pulley for the water pump?

[97_gq_lwb]

did you use a genuine thermostat .

[Yendor]

Does the electric cooling fan work? does it come on as soon as the air conditioning is turned on?

How's the radiator cap?

[zerolux]

Yeh all genuine stuff used, tropical thermostat 72deg, radiator cap is new and good, pulley is good...

[Sir Roofy]

just a punt here is the radiator cap the right pressure not to high

and your not locked into 4x4 with out knowing it

[zerolux]

Thanks guys for all the suggestions, I'm gunna flush the oil system and hope that helps (longshot) and replace the viscous fan anyhow as its the only part that isnt brand new in the whole cooling system, and lube the throttle body linkage in case the butterfly is getting stuck occasionally and leaning out the mix (another longshot), but as of right now, I'm stumped, and i've worked on and built motors since i was a kid, mind you, none of its been this computerised, electronic, sensors driven, flow controlled, temperature modifed, bleedin heart efi crap...just frustrated as it should be ice cold with all the new stuff..

only worry was the power loss when it started to get warm...woulda said head was cactus except all testing says otherwise...

I'll let ya'll know how it goes
Thanx again everyone

Jarrod