Unknown cause for 3fe running hot (14 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??

 

[jonheld]

The 3FE put out 155 bone crushing horses when it was brand new. A properly maintained cooling system should have zero issues keeping things cool.

Fan clutch Aisin FCT-049. Nothing else. These clutches are usually robust out of the box, but could benefit from higher viscosity fluid.
Fan shroud should be tight to radiator. I use adhesive backed closed cell foam to seal.
I periodically clean the radiators from the inside out using an HVAC cleaning wand. Mud, dirt, debris and crap will get trapped between the radiator and AC condenser coil. The condenser coil will catch all the bugs and road debris.
The radiator should have foam top and bottom to prevent air bypass.
The bottom "skid plate" that sits on the first crossmember by the steering damper should be in place.

With a cold non-running engine, the coolant level should be to the top of the radiator filler neck, and to the FULL line in the overflow bottle.
The coolant level in the overflow bottle should rise and fall with engine temp if your radiator cap is functioning properly.

 

[Marco Lau]

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

had had mine for over a decade now. I have overhauled my cooling system on and off for many years and yes i am positive..I have had a combination of top shelf radiator, green hub, tuned green hub with thicker oil, dual electric pusher fan up front for AC and tranny cooler, and now i finally settled on a dual elec. fans with controller. Its a labor of love for sure. Mine is on 37s and 6500 lbs. Even fully loaded and almost 7k in weight, it wont overheat even on long steep 8% climb in 100+F heat. Also, 3FE is a tough engine, and even above 225F + for a long duration of time, the engine will survive, and i have had my engine temp over 225+ for a few days @ the Rubicon and Fordyce due to a blown radiator, zero problems, but i wouldn't try that too often...

 

[dmjay]

had had mine for over a decade now. I have overhauled my cooling system on and off for many years and yes i am positive..I have had a combination of top shelf radiator, green hub, tuned green hub with thicker oil, dual electric pusher fan up front for AC and tranny cooler, and now i finally settled on a dual elec. fans with controller. Its a labor of love for sure. Mine is on 37s and 6500 lbs. Even fully loaded and almost 7k in weight, it wont overheat even on long steep 8% climb in 100+F heat. Also, 3FE is a tough engine, and even above 225F + for a long duration of time, the engine will survive, and i have had my engine temp over 225+ for a few days @ the Rubicon and Fordyce due to a blown radiator, zero problems, but i wouldn't try that too often...

Nice one. You will have this sorted in a jiffy.