Overheating HJ75 12HT

[TOJO 12-HT]

Hey my HJ75 with 12HT motor overheats. Goes to max on temp gauge sometimes within seconds, then back to run temp in very short time...

Rad has no grass seeds, mud etc blocking it, in side of rad looks n flows good, brand new water pump, brand new Toyota 82deg thermostat, flushed motor several times now.
Its got me buggerd, anyone have a idear maybe?

Also my bottom hose dosent get hot but top one dose

[CRUZAAMAD]

I know the 12ht runs a bigger radiator in the 60 series..
have you upgraded the radiator in the 75?

viscous coupling is usually the other culprit......

[TOJO 12-HT]

I know the 12ht runs a bigger radiator in the 60 series..
have you upgraded the radiator in the 75?

viscous coupling is usually the other culprit......

yeah your right but it winter 5deg outside atm up here n iv ran that setup over 2summers n it never got hot
viscous I first thought too, locked it up no difrence... iv now refilled it vith oil

[old ed]

I had much the same problem with my hzj75. I also did the waterpump, thermostat,radiator things. I finaly fixed it with a new (aftermarket) coupling. In your case I would be looking at the temp transmitter, It could be sending out a funny signal. If you have a mechanical style gauge this would not apply. The top hose should be hotter than the bottom of course so assuming you actualy have circulation the engine is probably not actualy overheating and it is a gauge malfunction.

[oldmate]

This is a common sixty series problem with the gauge. The engine isn't actually overheating. I believe it is repairable but most fit an aftermarket gauge.

[Herb05]

I would agree that it is a gauge or sender problem. If you can get a hold of a mechanical gauge and connect to check the difference between the two gauges this would isolate the problem. The other way is to use a infra-red temp gun when the gauge spikes to the hot position. Point it at the thermostat housing and this will give you a fairly accurate temp reading to compare to the factory gauge. Hope this helps.

[dogbreath_48]

Worth checking your body/engine/chassis earth's. An inadequate body earth sent all my gauges, lights and bells haywire.

[TOJO 12-HT]

new temp sender seames to have sorta fixed it
cheers boys n girls

[CRUZAAMAD]

get yourself a TM2 digital guage.

it will buzz an alarm if you burst a hose. and the alarm is definitely loud
as it has a sensor on the block, mine is under a bolt on the thermostat housing. 2H donga....

I can get that good of a readout I see the temps going up 10d on a hill

mind you ive now got to chase a broken wire to the sensor, and replace..
mind you it as out of warranty and TM2 sent another loom to replace for free
they answered the phone extremely promptly and the loom was sent express post, soo extremely happy with the service.

just got to get around to doing it