FJ62 Fan Clutch Tuning and Tech Help (1 Viewer)

[CaptHamster]

Hello all

I have been trying to remedy this issue with the fan clutch(es) on my FJ62 for months. I am beginning to lose my sanity, and I need to turn to the IH8MUD brain trust.

Backstory: Completely went through the cooling system a while ago, and stupidly threw out my working original fan clutch, because I had heard they should be replaced at the same time as the water pump. In hindsight, I wish I had not done thrown it out. Fan clutch was replaced with this AISIN unit from rockauto. Immediately noticed higher than normal driving temps on freeway, and definitely too high on long, steep grades. Also missing the loud roar from the fan engaging when hot.

I then read this thread from the 80 series forums about tuning the blue fan clutches, and this website about general fan clutch tuning. Discovered that the AISIN fan clutch for the FJ62 was not tuneable, but this one for the FJ80 (not FZJ80) was tuneable, and obviously fit the 3FE. Bingo, I thought, I'll just by the FJ80 clutch, tune it and drop in some good fluid and call it a day.

I have now done this 3 times over with the same results. Engine temps rise on long, steep grades to just under the red overheating mark on the stock gauge before I pull over and chicken out. Temps were verified by an IR temp gun at different spots on the radiator/thermostat housing/etc; gauge is not exact but appears to accurately reflect higher temps. When the vehicle is stopped and air is no longer flowing through the engine bay, the fan clutch seems to heat soak and engage; when engaged, the fan works great and drops temps very quickly. However, shortly after I pull away, it disengages and I lose my fan.

The core of the problem appears to simply be the fan clutch. The clutches are tuned to the max amount of adjustment, filled to the proper level with 10,000cst fluid, and installed behind a new CSF brass radiator with good flow and no obstructions. Simply put, I am losing my mind. The rest of the cooling system works as it should but I can't keep the damn thing cool when really working it, and short of tying the fan to the fan clutch or filling it completely full to get full-time engagement, I feel like I am out of options.

To me, it seems the AISIN clutch thermostat springs are simply tuned too high to engage properly for them to work, at least in our vehicles. Even at the lowest adjustment, I'm seeing radiator temps of over 230 degrees with no fan engagement. I don't know if there's any way to reach out to them and see if maybe I'm a unique case or if this is a production issue, but I need help... I want to drive my truck again without worrying about frying it on a hill.

Thanks in advance for the help, and for commiserating with me

 

[lovetoski]

If you still have your 62 fan clutch, run a few screws through it so it’s locked up. That is, engaged 100%. If u still have cooling problems, it’s not the fan clutch.

 

[WILLD420]

I’ve heard you can pin the spring in a new location to get lost couple sooner.

 

[Randy88FJ62]

Did you do the thermostat when you did the water pump and cooling system?

-thermostat o-ring / gasket installed?
-air burped out of cooling system?

 

[CaptHamster]

I’ve heard you can pin the spring in a new location to get lost couple sooner.

Would definitely be willing to try this, any info on how that's done?

Did you do the thermostat when you did the water pump and cooling system?

-thermostat o-ring / gasket installed?
-air burped out of cooling system?

Yes to all of the above. New t-stat, o-ring, gasket and t-stat housing installed and air was burped after refresh...

 

[CaptHamster]

Bumping in hopes for more help/info...

 

[Dynosoar]

Lock up the fan with some 550 paracord and see if your hot running issue is solved.

 

[RockDoc]

Fan shroud is in place? Nothing blocking air flow to and through (mud or such in the fins) the rad? I've had both bite me where either there isn't enough heat passing to the clutch to engage it, or the fan is ineffective at pulling efficiently through.

 

[WILLD420]

The spring turns the shaft in the front of the clutch. I've heard of pinning the spring fully engaged. I've also read that the shaft can stick or seize, try working the shaft back and forth. If it's tight, that is the issue. You can also tweak the spring to engage sooner.

 

[CaptHamster]

Lock up the fan with some 550 paracord and see if your hot running issue is solved.

I physically locked up the fan with paracord as you said, and temps never got hot like they had been doing. Like I said before, the fan definitely moves air and cools the engine when it works, it's just that it isn't engaging on its own without being forced to.

Fan shroud is in place? Nothing blocking air flow to and through (mud or such in the fins) the rad? I've had both bite me where either there isn't enough heat passing to the clutch to engage it, or the fan is ineffective at pulling efficiently through.

Fan shroud is in place, does not appear too tweaked and also has not been split down the middle yet (though I need to). The radiator is new and is very clean, the condenser is original but has been gently washed and rinsed, no obvious blockages, can faintly see light through the fins of the condenser and radiator.

The spring turns the shaft in the front of the clutch. I've heard of pinning the spring fully engaged. I've also read that the shaft can stick or seize, try working the shaft back and forth. If it's tight, that is the issue. You can also tweak the spring to engage sooner.

The spring has been tweaked already, it was adjusted by splitting the unit in half, loosening the screws and turning the plate attached to the spring. Would be interested in pinning the spring to an even tighter position if that's an option...

 

[mattressking]

Let me get this straight. At idle, temps are good? If so, fan clutch can generally be ruled out. If temps rise on climbs at speed, something else is going on. First simple question, at cold start, is fan locked up and then releasing after say ~1min or so?

At idle, not moving, and engine at operating temp, if it is not overheating, your fan clutch is not your problem. Bold of me to say, but that is the function of the fan clutch. At cruising and higher engine speed, the silicone loses its ability to keep the fan clutch locked and the fan clutch essentially begins to freewheel since the air flow over the radiator helps reduce coolant temperature. You don't want your fan clutch locked at higher engine speed as it will only increase the load on the motor.

A few questions:

1. How did you burp cooling system?
2. At idle and operating temp, are upper and lower radiator hoses hot?
3. Are you getting hot air from front and rear vents when heat is on in cabin?
4. After sitting overnight, how much coolant is in your overflow? Say at Low mark, High Mark, Middle of the two or nothing in jar, haha.
5. What is belt deflection like on your fan belt?

As one who has commuted up and down the grapevine at 100+ temps with Aisin aftermarket fan clutch...it functions as expected, so if trying multiple fan clutches hasn't solved it, we can simply deduce, that isn't your issue.

I know this sounds elementary but playing solve the coolant issue via internet gives us limited understanding into your engine.

 

[CaptHamster]

Let me get this straight. At idle, temps are good? If so, fan clutch can generally be ruled out. If temps rise on climbs at speed, something else is going on. First simple question, at cold start, is fan locked up and then releasing after say ~1min or so?

At idle, not moving, and engine at operating temp, if it is not overheating, your fan clutch is not your problem. Bold of me to say, but that is the function of the fan clutch. At cruising and higher engine speed, the silicone loses its ability to keep the fan clutch locked and the fan clutch essentially begins to freewheel since the air flow over the radiator helps reduce coolant temperature. You don't want your fan clutch locked at higher engine speed as it will only increase the load on the motor.

A few questions:

1. How did you burp cooling system?
2. At idle and operating temp, are upper and lower radiator hoses hot?
3. Are you getting hot air from front and rear vents when heat is on in cabin?
4. After sitting overnight, how much coolant is in your overflow? Say at Low mark, High Mark, Middle of the two or nothing in jar, haha.
5. What is belt deflection like on your fan belt?

As one who has commuted up and down the grapevine at 100+ temps with Aisin aftermarket fan clutch...it functions as expected, so if trying multiple fan clutches hasn't solved it, we can simply deduce, that isn't your issue.

I know this sounds elementary but playing solve the coolant issue via internet gives us limited understanding into your engine.

I appreciate the response. I'll go down the list:

1.) System was burped by putting truck on wheel ramps, running from dead cold to warm with rad cap off until bubbling stopped or coolant began to flow out, radiator was capped, then engine stopped and overflow tank filled with 50/50 coolant. Wash, rinse, repeat until the overflow tank rose to the "MAX" line when the engine was warmed up.

2.) Upper hose is definitely hot when engine is warmed up and idling. Honestly, have not checked the lower hose. Will definitely check that tomorrow.

3.) Yes, I get hot air from both front and rear vents when engine is warmed up and heaters are on. Although the front heater temp does fluctuate a little bit when it's not on full MAX hot.

4.) After sitting overnight, coolant overflow bottle falls back to very bottom of the tank. When at operating temp, it sits just below the "MAX" level but drops down after cooling off.

5.) Belt deflection is fine, unfortunately I have changed fan clutches multiple times over last six months, so have had to loosen and re-tighten the belts multiple times. They don't squeal and don't seem to be lugging the engine, so I assume they're in the right area of tightness. Deflection on the fan belt is not much, maybe 1/2 inch on the longest run of it?

Again, appreciate the response; I don't mind going back to basics to make sure I haven't missed anything. It's been a long ongoing process and it's entirely reasonable that I could have missed something simple. I'm hoping it isn't actually the fan clutch, because that was honestly one of my last options I was looking into.

 

[FJ60Seth]

Others will disagree, but my experience is that a faulty fan clutch will cause overheating under load. Symptoms were similar to yours. Normal temp at idle, no load. High temp at full throttle on a long incline. I locked up the fan clutch with paracord cord, like Dinosoar suggested, & over heating stopped. Replaced fan clutch and symptoms never returned.

 

[CaptHamster]

Wanted to update this in case anyone is curious.

Finally resolved the problem, and it ended up being the fan clutch again. Ordered a new blue hub clutch from rockauto, split them in half and got a couple pans of water going to test opening temperatures.

The first blue hub clutch I had, even when fully adjusted to open as low as possible, was not opening until approximately 115 degrees fahrenheit. The red hub clutch, specifically for the FJ62, does not have any adjustment built in to the clutch, and did not open until 120 degrees! Luckily, the newest blue hub clutch (for the FJ80) opened at a happy ~95 degrees after adjustment, and since installing on to the truck, temps are back to normal and operation is as good as it was before all this started.

Not sure if I got a couple fluke fan clutches, or if quality control at AISIN is not top notch, but I'm glad that at least one worked correctly. All the previous clutches have since been returned. Hope this helps someone else in the future, and thank you to all the helpful replies...

 

[LAMBCRUSHER]

Ok... I’ll try to go back and read up but I’ve done the clutch mod and it’s been great... aqua hub clutch some 11k and 15k I think silicone clutch juice from rc car shop at 50 50 mix AFTER cleaning and tuning... water bath, hot plate, thermometer, and screwdriver if I recall... it’s a matter of loosening a screw and clocking the timing plate to just opening at a certain temp and the being fully open at another... think I’m opening at about 100 and fully open by 150 it 60... yeah it runs on all but cold days nights and mornings but it’ll also keep temp at 3400 rpm with the ac on in Fresno summers... I used to have heat overrun issues till I did the mod, now it’s been fine.

 

[LAMBCRUSHER]

Crap... we’ll, I read up... good work!lol!