fan clutch

[landtank]

Rick:
I've read your methodology with great interest. My concern is that your technique has effectively raised the rpm of a given fan. As I found out the hard way, over ~4500>redline, this absolute fan rpm becomes a recipe for fans eating radiators. A less viscous fluid would do two things IMO, come on sooner (good) and increase absolute fan rpm (bad or ugly or worse). Thoughts?

I've pretty much come to the conclusion that runs to redline on these trucks and overall reduction in heat would be best accomplished with electric fans. You lose a lot of nose cone weight and balance issues (more with SC spacers in), you can over ride the fans to 'off' when "water crossing", you can pick a variety of fan speeds, CFM, sizes, number, and many turbo cars have some impressive fans with circuits (I had the tape measure on a turbo volvo one just this afternoon). Summit actually carries some pretty impressive 5600cfm dual fan units that use a progressive speed thermostat, and smart relay control that has over ride for Fan on-A/C, Fan on-override, Fan off-override, and LED status.

So 'best option' might need to include 'for an engine driven fan', but I'm convinced electrics can add more flexibility with a lot of benefits I just don't see with hte engine driven fan as I move my supercharged 80 toward redline.

Your thoughts?

Scott Justusson

Scott, one thing to remember is I had a clutch that allowed the engine to run extremely hot. So while I might have advanced the clutch's timing by 10* it was on a clutch that when the engine was at 240* it provided no drive to the fan at all.

So a clutch that provides some cooling, but still allows an engine run slightly hot, adjusting that clutch to the same spot as mine would be less of an advancement to it, maybe something like 5* or even less.

The fear of over driving the fan was a concern to me as well and why I've avoided thicker oil all together.

Again my clutch wasn't coming on at all. The needle on my modified gauge was pegged over the red and the clutch had no drag on it at all. So I'm not worried about over driving the fan. And I'm not advocating that people take some readings on their clutch and automatically advance it 10*, which could put you in an over drive situation, but actually setting it to a specific temp which would yield different amounts of adjustment for different clutches.

As far as the electric fans, I don't see a need for it right now.

 

[SUMOTOY]

Scott, one thing to remember is I had a clutch that allowed the engine to run extremely hot. So while I might have advanced the clutch's timing by 10* it was on a clutch that when the engine was at 240* it provided no drive to the fan at all.

So a clutch that provides some cooling, but still allows an engine run slightly hot, adjusting that clutch to the same spot as mine would be less of an advancement to it, maybe something like 5* or even less.

The fear of over driving the fan was a concern to me as well and why I've avoided thicker oil all together.

Again my clutch wasn't coming on at all. The needle on my modified gauge was pegged over the red and the clutch had no drag on it at all. So I'm not worried about over driving the fan. And I'm not advocating that people take some readings on their clutch and automatically advance it 10*, which could put you in an over drive situation, but actually setting it to a specific temp which would yield different amounts of adjustment for different clutches.

As far as the electric fans, I don't see a need for it right now.

Thanks for the clarification Rick. My experience with electrics is much greater than with mechanical, or at least 1 of each in everything that I routinely work on. As the price of fuel continues to rise, I'm thinking that finer control over engine temps/cooling can yield gains in HP, reliability, optimum operating temps, gas mileage and address a myriad of other problems I read here with 80 cooling.

One side note. As I was playing around with expansion valve and pressure switch replacement on my 80 today, I noticed some interesting A/C pressure issues caused by low airflow thru the condensor (me shroudless and cut blades). The FSM diagnostics and the Snap-on A/C machine confirms my thinking that the shroud is really there for A/C condensor efficiency. With high pressure climbing on both sides (FSM AC-23 No. 4 - insufficient cooling of condensor - ck fan motor operation - me thinks shroud too). This would only manifiest itself at idle on my truck. And why most vehicles use an aux electric fan trigger at high pressure switch in addition to the clutch driven motor fan. In my case, we found the problem was in the switch not cutting off the compressor, causing overpressure of the complete system. I suspect a properly operating compressor cutoff switch will solve that, but I also expect less than optimal A/C operation at idle as I'm equipped now.

These electric engine fans on the volvos look pretty beefy, and have a intercooler and condensor in front of the radiator, and the motor is low profile, includes a dual resistor in the fan, and the relay pack is all within a couple inches of the fan itself. Looks like a good transplant candidate to me. Maybe even two of them, because I can.

Good work and writeup on the procedure Rick. I still have concerns that this adjustment you did on a properly functioning clutch could result in overspin of the fan blades.

Scott Justusson

 

[landtank]

I still have concerns that this adjustment you did on a properly functioning clutch could result in overspin of the fan blades.

Scott Justusson

Ahhhh, why would you adjust a perfectly good working clutch?

 

[Tools R Us]

I doubt that your going to overstress a stock fan that's in good condition with a working fan clutch installed on a stock truck. The fan clutch is a fluid coupling, it can only transfer so much torque. Even with thick fluid in them, they can be stopped and held by hand.

The blue hub is the finest clutch I have ever had apart, big beefy cooling fins, good fluid capacity, very nice valve setup, top notch machining and construction. It's wimpy output is I believe a Toyota decision, they bent to the US preference for quiet motors and fuel efficiency, over maximum cooling. Their thinking probably was something like, most of these are only used to take the kids to the game, so we can get away with 3000cst and a late valve timing.

If you live in a cool climate and don't use the truck hard the stock one may work OK? If your working the truck hard and/ave a less than perfect cooling system, a slight valve tweak maybe enough? For my hot climate and working it hard, it's getting thicker fluid and maybe a valve tweak.

Some fluid clutches are centrifugal, only work at low RPM's. The most common type have stepped valves, having one or more "speeds". The blue hub's thermostat valve is variable, it attempts to keep the airflow at the temp that it's set at. When it senses a temp rise it open slightly, when the airflow cools it closes slightly, almost always delivering some torque, but it should never be fully "on" or open unless the motor is overheated. It's job is to keep the airflow at an even temp, much like the thermostat works for the coolant.

By changing the valve setting, you change the range where the valve is set to be on, lowering the airflow temp that it's trying to maintain. This may work, but I see it having the same effect as switching to a cooler thermostat when the motor is overheating, you get a head start on the cooling, but when it sees big load and/or temps the fluid may not have the capacity to deliver the torque needed.

By switching to a higher viscosity fluid, when the valve opens the effect on the fan is greater, pulling more air, cooling the airflow quicker, allowing it to react to loads faster and close sooner. With a higher viscosity fluid, the valve will operate in a smaller range allowing more capacity for higher loads. More like adding a larger radiator to an overheating engine.

 

[landtank]

By switching to a higher viscosity fluid, when the valve opens the effect on the fan is greater, pulling more air, cooling the airflow quicker, allowing it to react to loads faster and close sooner. With a higher viscosity fluid, the valve will operate in a smaller range allowing more capacity for higher loads. More like adding a larger radiator to an overheating engine.

On this I'd have to disagree. The temp spring is designed for a specific amount of movement for a given temp range. That thicker oil will not flow through the valve at the same rate so the clutch lockup with respond slower than if it had thinner oil.

I'm betting that a properly setup clutch will stay ahead of the needs of the truck so that an overheat situation will be avoided and the need for a heavy lockup isn't neccesary.

I'll know this by 15:00 tomorrow after my trip to the Cape, the Imperial is going along as a spare.

 

[Tools R Us]

On this I'd have to disagree. The temp spring is designed for a specific amount of movement for a given temp range.

Agree

That thicker oil will not flow through the valve at the same rate so the clutch lockup with respond slower than if it had thinner oil.

From my research disagree;

It's less about oil flow speed and more about the thicker oils stronger shearing, transferring more torque to the fan. If you were seeing temp spikes into the danger zone before, the valve was probably mostly or all of the way open, shearing the oil to the maximum of it's abilities. With the valve mod you may stay ahead of the heat load and work for your cooler climate, but leaving little or no capacity for emergency.

One of the questions I asked the engineer was, how is the oil's shearing properties lost? His reply was, "Pure silicone fluid is very stable, if not contaminated or heated to 300F+ it will maintain it's properties virtually forever, never wear out."

The fan clutch runs in a hostile environment, but only at about 150F and the Asian clutch has big cooling fins. I have refilled many dead ones and they worked like new, with only new oil added, so there has to be some mechanism that causes that heat internally? He replied, "if the oil is sheared within it's design range little heat is produced, if it's aggressively sheared much more heat is produced, as it's heated it's ability to shear is reduced, forcing it to work harder, causing more heat, etc. until some or all of the oils properties are lost and if they are lost by overheating it's permanent."

So what is the best fix? His reply was, "use a more viscous fluid with higher shearing ability, so that the normal shearing is lower in it's range and you have more reserve before overstressing, degrading the fluid. The valve will still operate the same, but the fan will react faster and you will see more stable air temps in the shroud. With the proper fluid for the application you should never have a fluid related failure."

He asked if the Asian clutches could run thicker fluid? I said that Toyota sells 3000, 6000 and 10000cst and I have run 10000cst with good success. He recommended starting with ~15000cst, that is a sweet spot viscosity for high temp shearing and would work well for my environment.

So that's where I stand, new fluid on the bench and a broken hood latch cable, waiting on a replacement on it's way from Dan, so I can open the hood and test it out.

I'm betting that a properly setup clutch will stay ahead of the needs of the truck so that an overheat situation will be avoided and the need for a heavy lockup isn't neccesary.

Agree

I'll know this by 15:00 tomorrow after my trip to the Cape, the Imperial is going along as a spare.

So if you have faith in this mod, why the spare? I am betting it will work, the blue hub works and is a good choice for a truck in good condition, driven how most Americans drive them. When pushed hard or with a compromised cooling system it has marginal excess capacity. With minor mods to the valve and/or fluid change it would be bullet proof. If the engineer's theory on fluid overheating is correct, combined with the numb coolant gauge, I have to wonder how many headgasket, radiator, cooling, etc. problems could be traced back to cooked fan clutch fluid?

 

[landtank]

Good info, the oil in the clutch was a golden color and the new stuff going in seemed to be clear.

But I'm still thinking my problem was also related to timing as the clutch wasn't the least bit engaged when I was way over heated. And now after the timing adjustment it seemed to work near perfectly.

 

[SUMOTOY]

A couple more thoughts for LT and TRU (good discussions). The operation of a fan clutch is basically the same as a Viscous Coupling (found in later 80 HF2AV diffs). As heat rises, the sheer properties become non existent and it becomes just a hot lube (called humping in a VC). In the fan clutch, you have two adjustments, timing and flow (sheer).

I'm trying to figure out a way to data log these differences (lockup vs temp), but I believe in strictly hydraulic clutches there are too many variables (including ambient temp) to make this meaningful. I also believe that engine driven fans (exclusively) have a very wide range of operation, especially in an 80. Add in a A/C condensor that needs a lot of flow at low vehicle speeds, and creates a massive amount of clutch heat/radiator heat/underhood temps, I can see why most later vehicles with engine driven fans also use a electric fan with A/C pressure activation (low flow through condensor, low engine speed causes high A/C pressure on both sides of expansion valve).

My own thinking is that those of you playing with the stock engine fan and thermostat should hook up a pusher fan in front of the radiator, that uses the A/C pressure switch circuit for activation. In pre 94 80's this is a 3 position switch (hi/med/low), on 94> this is a 2 position switch (hi/lo). The reason for this is simple, A/C pressure rises as flow thru the condensor (and radiator) is reduced. Side benefit, mommy gets cool air in traffic.

Those of you (me included) that want to use an electric setup have a better chance of exact control of engine temps, since electric fans don't have ambient temp as a variable to operation. That is the biggest drawback to me about engine driven fan clutches. Ambient temp, vehicle speed and A/C operation are all variables that affect it's operating range, read this hydraulic operation only is not ideally directly/exclusively related to engine temps.

However, adding a pusher fan off the A/C circuit can certainly increase the life of the stock fan clutch, and create a better hybrid hydro/electric setup.

Good stuff boys.

Scott Justusson
QSHIPQ Performance Tuning

 

[Tools R Us]

The operation of the viscous coupling is more complicated and works in short bursts with much higher loads than the fan clutch. But I agree that the "humping" needs to be avoided, by selecting a fluid with more searing capasity.

Not a big fan of hydraulic or electric clutches, too complicated for good reliability and I don't think they are any better at controlling temps than the simple stock fluid coupling.

I agree on the A/C pusher, but think that simply wiring it to the clutch circuit is better. When wired to the pressure switch the pressures are already high when it's activated. Wired to the clutch you get the benefit of better airflow, lower vent temps the whole time the compressor is on.
https://forum.ih8mud.com/showpost.php?p=596415&postcount=48

I think if you did some monitoring of temps, you would find that the shroud air temp is a good and probably better indicator of total heat load than a coolant sensor. Because it takes into
account the ambient, A/C, trany and any other loads.

I have a lot of experience with electric setups also and wouldn't run one as a primary on my truck, for the following reasons; The stock setup driven by two belts is simple, powerful and reliable, things I value in a truck that is run in remote locations. To come close to the power of the engine driven fan it will require big electrical loads and I have other "needs" for the rather limited electrical generating capacity that the truck has. The stock system is simple and easy to "booty fab fix" in remote locations, an electric system is much more complicated to diagnose and repair with limited resources.

All of the electric setups that I have owned and/or worked on relied on a coolant sensor in ether a simple on/off or stepped mutable speed setups, most also kick on with the A/C. So the sensor looks for the coolant to heat to it's preset temp, turns on and runs until it reaches it's turn off temp, making a stepped heat profile, hot, cool, repeat. Sure you can add more fans and more control methods, farther complicating the system, but I will bet that you will never come close to the power, reliability and even temp control of a good simple belt driven fan, using the electrical output of the 80?

 

[CreeperSleeper]

Personally, I think I would like to replace my fan and clutch with a spacer and a metal flex fan as well as an aux elec fan for the AC. (I don't care about the extra noise... that's what my subs are for!) Is there any other downsides to doing this?

 

[SUMOTOY]

The operation of the viscous coupling is more complicated and works in short bursts with much higher loads than the fan clutch. But I agree that the "humping" needs to be avoided, by selecting a fluid with more searing capasity.

Kevin, I don't agree that it's searing capacity. Any silicone fluid has a potential heat problem, that affects it's shear ability. A viscous coupling is actually quite simple, it uses the same shear forces of silicone. The principle to a fan clutch is identical, so is the fluid.

t a big fan of hydraulic or electric clutches, too complicated for good reliability and I don't think they are any better at controlling temps than the simple stock fluid coupling.

We disagree. A VF is always running, whether cooling is needed or not. It's simple, but it does fail, and quite regularly if we read the posts/views on viscous thermos here. I personally believe they fail from excess heat, and the most likely culprit is from low vehicle/engine speed operation with a heat soaked condensor in front of the radiator.

I agree on the A/C pusher, but think that simply wiring it to the clutch circuit is better. When wired to the pressure switch the pressures are already high when it's activated. Wired to the clutch you get the benefit of better airflow, lower vent temps the whole time the compressor is on.
https://forum.ih8mud.com/showpost.php?p=596415&postcount=48

For a pusher aux fan (to stocker or electric primary), I would only want it operating when the high pressure switch is activated. All the time on a pusher can actually obstruct airflow thru the radiator. If you are using only electrics on the pull side, compressor output voltage is fine, but I'd be tempted to use the medium pressure circuit that is unused in the 94> trucks using pressure switch PN 866450-08010. This brings pressure up in the system faster, and then allows the primary fan to do the overtime work. This addresses many of your concerns regarding draw.

I think if you did some monitoring of temps, you would find that the shroud air temp is a good and probably better indicator of total heat load than a coolant sensor. Because it takes into
account the ambient, A/C, trany and any other loads.

I'm not trying to account for those loads, I want the total load to result in a constant engine temp. I've been thru this discussion already several times. In reality all those variables result in a engine water/oil temp. The reason most manufacturers went to at least dual systems, is that VF are oversimplified and aren't designed to handle A/C systems well (it doesn't know the difference between engine overheat and condensor heat, a coolant temp sender does) As we start to focus on optimal fuel consumption, heat management will be/is the key. Electrics address this very well, with very simple ciircuits.

I have a lot of experience with electric setups also and wouldn't run one as a primary on my truck, for the following reasons; The stock setup driven by two belts is simple, powerful and reliable, things I value in a truck that is run in remote locations. To come close to the power of the engine driven fan it will require big electrical loads and I have other "needs" for the rather limited electrical generating capacity that the truck has. The stock system is simple and easy to "booty fab fix" in remote locations, an electric system is much more complicated to diagnose and repair with limited resources.

Problem: Most offroaders are going to electric fan setups. The reason? Because low speed engine operation in crawling isn't up to the task, and water crossings tend to eat engine driven props, electrics can just be shut off. 20 amps for max draw 4600cfm with a truck at idle doesn't sound overwhelming, and offroaders with dual batteries can handle this without a problem. Or shut down 2 100w hellas. I've booty fab fixed my 80 radiator 6 times at 7300ft and below zero weather (see posts and procedure). I've also replaced a whole electric fan and shroud at a race in under 5 minutes. Diagnostics? fan switch (jumper to ck while installed), relay (jumper to ck while installed) and fan motor. A spare 40 amp relay is 6 bux, a fan switch is 30. A spare motor with fan in a junk yard, 5 bucks? Just the VF thermo is 75 and a spare fan is another 75. I'm not with you here Kevin.

All of the electric setups that I have owned and/or worked on relied on a coolant sensor in ether a simple on/off or stepped mutable speed setups, most also kick on with the A/C. So the sensor looks for the coolant to heat to it's preset temp, turns on and runs until it reaches it's turn off temp, making a stepped heat profile, hot, cool, repeat. Sure you can add more fans and more control methods, farther complicating the system, but I will bet that you will never come close to the power, reliability and even temp control of a good simple belt driven fan, using the electrical output of the 80?

Ck out the toys summit makes for the offroad trucks Kevin. Specifically look at that controller that gives progressive voltage to the fans, with status lights, A/C feed, override on/off (for water crossings) and CFM output at truck idle speeds that the 80 can't do cruising 60. All with less than 30 amps, several duals under 20.

I'm looking at this only for practical application and ease of operation. Most stock car electric fan circuits are independent and easily/cheaply grabbed complete at a yard. Turbo applications have some pretty impressive fans with low load, if that's your target.

There is no question in my mind as fuel starts it's climb towards 4bucks/gal, that changing the cooling system of our trucks to be more accurate, has direct benefit to the wallet, and our trucks don't have to suffer overkill for 80% of it's duty life. Why not choose your temp switch accurately on an electric circuit that brings the 80 with A/C into the mainstream of modern cars and trucks?

my .02

Scott Justusson

 

[Tools R Us]

I too have changed electric fans in the pits and that's not something that I want to do on the trail or carry a spare fan. I have diagnosed and repaired many fan systems, electric, hydraulic, viscous fluid clutches, direct belt drive and electric fans. In my 20 year experience as an import tech the electric is by far the least reliable. I don't see a dozen+ electoral connections, relay(s), fuse(s), electric motors exposed to dust, dirt, mud and water ever being more reliable than a simple sealed viscous coupling.

Where did you get this? "Problem: Most offroaders are going to electric fan setups." Why would this be a problem? If they decided to go that route it wouldn't be a problem for me, but that statement is absolutely false in my experience. I have been known to hit the trails pretty often including national events with loads of trucks and the percentage of electric primary fanned units is the very small minority. Most have them because of packaging issues, engine swaps, buggies, etc. not because they are somehow better or more reliable. I cant think of one HD offroad truck that comes with an electric primary fan, if they were better for a heavy duty applications you would think that the manufactures would be putting them on? Fact, most new cars that have electric primary fans are because of packaging issues, transverse engines, low aerodynamic body work, etc. that don't allow for a conventional belt driven fan and radiator setup.

I have swapped electrics in several cars and one truck. We put a Taurus in a buddies 22R powered truck, it has worked marginally OK, but it is 5spd, no A/C or power steering, so it's cooling requirements are much less than my 80? Several locals have swapped to electrics and put them back to stock for better cooling performance.

On the parasitic draw issue, thermostat controlled viscous fluid clutches draw very little when the valve is closed. Prove it for yourself, start the truck cold, let it run a minute or so to pump the fluid into the reservoir, then grab the fan, you can hold it with just a fingernail until the fluid leaks out of the reservoir from not spinning. If the electric fans had a usable horsepower or miles per gallon gain the manufactures would put them on all vehicles to help them meet the EPA standards.

On the water crossing issue, most fan problems I have seen were from improper technique, water entry too fast, not fan type. With a thermostat controlled viscous clutch, on water entry, the water very quickly cools the thermostat and within a few seconds the fan is freewheeling. I have had the hood open with the motor running and the fan is stopped due to a couple of blades in the water! Direct drive fans are the worst for deep water, but a buddy damaged his radiator with an electric, by forgetting to turn it off. Most electrics mount very close to the radiator, so it's easy to cause damage if not turned off.

So we will have to disagree, if your comfortable going electric go for it, but my truck will stay belt driven and my Camry will stay electric. It may have to do with differing views on cooling needs? I just got back from a trip to pickup metal for a C-Dan project and the radio announced that it was 116F and sunny as I was setting in traffic!

 

[Tools R Us]

Kevin, I don't agree that it's searing capacity. Any silicone fluid has a potential heat problem, that affects it's shear ability. A viscous coupling is actually quite simple, it uses the same shear forces of silicone. The principle to a fan clutch is identical, so is the fluid.

The fluid is the same and both shear it, but the viscous coupling has multiple movable plates that contact each other to deliver greater torque, called humping. The fan clutch is a much simpler design, only one plate with a fixed shearing gap, no contact or humping.

http://webpages.charter.net/raventai/HF2AV TRANSFER.pdf

 

[SUMOTOY]

The fluid is the same and both shear it, but the viscous coupling has multiple movable plates that contact each other to deliver greater torque, called humping. The fan clutch is a much simpler design, only one plate with a fixed shearing gap, no contact or humping.

http://webpages.charter.net/raventai/HF2AV%20TRANSFER.pdf

TRU
Plates in a VC 'can' touch each other, but they aren't meant to. Humping is the same as VF overheat. The silicone is too hot, which means the plates touch. In a VC, humping is not a long term application, it's more a clear sign that it will fail. A fan clutch doesn't have plate to plate contact, but it can overheat the fluid, which also causes failure of the unit.

They are both simple designs, the advantage to the VC is that it's a sealed unit inside a bath of trans fluid. A VF is a sealed unit exposed to very hot environmental temps (ambient + condensor + radiator + engine heat).

Scott Justusson

 

[Tools R Us]

Plates in a VC 'can' touch each other, but they aren't meant to.

Wrong, the VC plates are designed to touch.

Humping is the same as VF overheat. The silicone is too hot, which means the plates touch. In a VC, humping is not a long term application, it's more a clear sign that it will fail.

The only thing here that is correct is; "humping is not a long term application". The rest is wrong, Humping is a design feature to provide added torque transfer, it has nothing to do with "a clear sign that it will fail." If you would like to read more about the design features, this is the transfer case section from the '96 LX450 new vehicle features document;
http://webpages.charter.net/raventai/HF2AV TRANSFER.pdf

A fan clutch doesn't have plate to plate contact, but it can overheat the fluid, which also causes failure of the unit.

Correct, technically Toyota calls them unserviceable, so when the fluid is cooked they are replaced. But it an easy procedure to change the fluid and by picking a better fluid for the local environment the performance can be tuned and life will be improved.

They are both simple designs, the advantage to the VC is that it's a sealed unit inside a bath of trans fluid. A VF is a sealed unit exposed to very hot environmental temps (ambient + condensor + radiator + engine heat).

Correct, they are both well designed and long term proven to work in their environments.

 

[SUMOTOY]

Wrong, the VC plates are designed to touch.

They 'can' touch without failure. Problem, humping is defined as overheating of the fluid. As such plate contact will provide momentary increase in torque capacity, but enormous amounts of heat is generated. This can and does cause VC failure, it is THE primary cause of failure of a VC. Well documented in fact.

The only thing here that is correct is; "humping is not a long term application". The rest is wrong, Humping is a design feature to provide added torque transfer, it has nothing to do with "a clear sign that it will fail." If you would like to read more about the design features, this is the transfer case section from the '96 LX450 new vehicle features document;
http://webpages.charter.net/raventai/HF2AV%20TRANSFER.pdf

It's not a long term application, because it is by definition an overheat of the silicone fluid within it. Excessive time in the 'humping' phase of a VC will cause it to fail. This is a known property of silicone overheat in a VC. It can operate in a humping state, but technically it's a failure mode of it, the silicone is too hot to provide the proper shear properties. The 'benefit' of it's failure mode is that the plates will touch causing a massive amount of extra torque transfer, which Ferguson et. al. hope gets the respective axles back to equal rotation.

Correct, technically Toyota calls them unserviceable, so when the fluid is cooked they are replaced. But it an easy procedure to change the fluid and by picking a better fluid for the local environment the performance can be tuned and life will be improved.

Replacing fluid can be done. My question is more obvious, why does it cook? My claim: Because it's regularly exceeding a 300F operating environment. That summary explains why folks with brand new 'blue' thermos still overheat. Servioce Life isn't improved necessarily, it's replacing cooked fluid with new. It's not improved if you haven't done anything to address the 300f environment.

Correct, they are both well designed and long term proven to work in their environments.

I'm quite enjoying the discussion, and will attempt to move it forward to some numbers attached to my reasoning, and maybe that will generate agreement instead of mindset. Without question, we have folks here that have heat related problems with brand new "blue" engine fan thermos. Why? Could it be that the fluid is cooking in them? Absolutely. Where it is most prone to do so, high ambient, high load, low engine/vehicle speed, A/C condensor heater.

I propose that the answer and data is found in the A/C system. If we look at the tables of 134a pressures vs the FSM, we know that at high pressure, there isn't enough (any) exchange at the condensor, in fact it's heat soaking from the radiator. At the 412psi cutout, the condensor temp is 186F and climbing. It 'normal' operation is defined by Toyota as 135F (210psi). So a 186 temp is an airflow problem, pure and simple.

TRU, I've done a lot of research on cooling systems over the years. I've now measured my A/C system on my 80 and can translate all the pressures I've measured to temps. As I believe you are in a mindset that all is fine, I'll start a separate thread on some of the knowns. What we don't know (maybe IDoug or Dan can help here) is what rpm vs CFM ratings are on a given 80 fan/clutch arangement. We certainly know several of the electrics, since Summit publishes them. I propose, in actual PERFORMANCE, you aren't going to outperform a dual electric fan with the engine driven one, at any rpm. I propose you won't outperform a single electric fan at low engine rpm.

I propose these conclusions based on my measures of my A/C pressures, since I can translate those into condenser temps.

There is a reason very few standalone engine fans exist in the market right now. Thanks for the thoughts Kevin, I hope we all learn something. As I have a lot of information to put forth on this subject I'll divide it into parts. First will address the obvious need for aux cooling. I await your review, since I'm only a performance guy, without mindset for now.

Cheers

Scott Justusson
QSHIPQ Performance Tuning
94 FZJ80 Supercharged