Unknown cause for 3fe running hot (4 Viewers)

[SciroccoDamonte]

Running hot has been a steady issue I’ve had in my time owning my 1991 landcruiser. At first it was just the fan clutch and that seemed to fix most issues. But then it cropped back up again. I decided to do a full revamp of the system. New water pump, new aluminium 4 row radiator, new thermostat. The issue seemed to still persist, then I thought it was possible it was the gaps in front of the radiator that would let air by without going through the fins. That’s yet to be tested but I doubt it would make that much of a difference. I’ve done compression tests and all cylinders are good. It mostly gets hot at idle and when I’m on steep incline 4wding. Anyone that has a lot of experience with 3fe’s have any ideas? Not sure what else to do.
Thank you

 

[OGBeno]

A few questions:

1. What is "hot"?

2. How are you measuring said hot?

3. What is your baseline for "not hot?"?

 

[SciroccoDamonte]

A few questions:

1. What is "hot"?

2. How are you measuring said hot?

3. What is your baseline for "not hot?"?

Hot is when the needle on the gauge raises above the baseline middle, I live on the coast and the truck never has issues, but recently I moved to susanville ca (higher elevation higher temp) and just idling will get the needle up.

I’m just using the gauge

Because the gauge on the 80’s is slow I know the truck is running cool when the ac works, and often the ac will start blowing warm before the needle changes.

 

[CJF]

I know the truck is running cool when the ac works, and often the ac will start blowing warm before the needle changes.

No high-temp AC cutoff on a 91, so that seems to point to fan clutch. How old is your clutch and what brand? Do you hear it roar on startup?

 

[SciroccoDamonte]

No high-temp AC cutoff on a 91, so that seems to point to fan clutch. How old is your clutch and what brand? Do you hear it roar on startup?

Well it’s not that the ac cuts off it’s just that it gets so warm in the engine bay that the ac can’t keep up. Fan clutch is Aisin and brand new. It’s stiff and good so I really don’t think it’s that.

 

[Marco Lau]

Perhaps i may chime in...own my 91 for over a decade now. Plenty of 4Lo type wheeling.
1st thing 1st. - Install a aftermarket temp sensor on the upper rad. hose with some real-time reading. The factory gauge sites in the middle between 150-220F
@ 225F - 230F needle starts to rise to 3/4 and AC swill shut off and coolant dumping out of overflow in an attempt to shed extra heat.
#2 get an OEM green Aisin hub along with a new radiator/ Alum. preferred, new cooling system and all. You should be able to cruise @ 190F all day on the highway and 210-220F on steep grade 2nd gear is normal.

 

[CJF]

@ 225F - 230F needle starts to rise to 3/4 and AC will shut off

On a 91-92 3FE? You sure??