Is new fan clutch really needed when changing water pump? (1 Viewer)

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I have a 'modified' blue fan clutch....BUT I live in Texas (read very hot here). YOU would not benefit in any way from a fluid modded fan clutch in your climate. However, I would suggest replacing your current fan clutch with a stock Aisin Blue Clutch.

If your fan blades feel flexible....then you're good to go with that.

Nice! Yea, having the mod clutch in Texas definitely makes sense. It looks like the new blue AISIN clutch w/o mod is the way to go in my case then. Blades are flexible indeed.

Thanks for sharing the info!
 
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There are drawbacks to modding the clutch, specifically it will drain horsepower and mpg.
That has not been my experience. I went from an OEM blue hub to the Wits End/Landtank fan clutch at the end of 2016 and there was no change in economy according to my UltraGauge. The benefits of a significantly tighter temperature swing cannot be overstated.
 

richardlillard1

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Eatons can be drained and refilled, but have an anti drain back valve built in, so you need to heat the spring to open the primary valve then put something in it to keep it open while draining the clutch. A small screw works well for this And I find that draining the clutch face down is best. I typically put anywhere from 20-30k cst in an Eaton and set the valve to open around 115-120° for desert climates.

The higher the cst, the more draw the clutch will have on the engine’s power. finding a balance for this is up to the individual, but I find that an 80 on 37s is already slow, so I’d rather have the vehicle run as cool as possible.
 
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Eatons can be drained and refilled, but have an anti drain back valve built in, so you need to heat the spring to open the primary valve then put something in it to keep it open while draining the clutch. A small screw works well for this And I find that draining the clutch face down is best. I typically put anywhere from 20-30k cst in an Eaton and set the valve to open around 115-120° for desert climates.

The higher the cst, the more draw the clutch will have on the engine’s power. finding a balance for this is up to the individual, but I find that an 80 on 37s is already slow, so I’d rather have the vehicle run as cool as possible.

Alright, thanks for the explanation. How would you go about heating the spring up and setting the valve to a specific temp?
 
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That is the info that I have been looking for. Thanks for sharing. I didn't know about those drawbacks either, could you explain the reason for the clutch mod draining horsepower and affecting the mpg?

I think i'll wait and get a new AISIN stock clutch and finally be done with the cooling system. If needed, i'll mod it later and still have the Eaton one as a spare just in case.

Well, onto the next item on the list.....that phh :borg: ow boy....
That has not been my experience. I went from an OEM blue hub to the Wits End/Landtank fan clutch at the end of 2016 and there was no change in economy according to my UltraGauge. The benefits of a significantly tighter temperature swing cannot be overstated.

Modding the clutch usually involves lowering the temperature at which it engages and using a higher CST oil (thicker), which makes it pull more air, in essence spin faster at a given RPM. Logically, both of these effects are going to use more energy, or horsepower. There really is no argument against this. To do more work requires more power. That power is finite, so the horsepower left over for locomotion is reduced. I suppose one could say that total horsepower is not reduced, which is technically true, but some of it is used to power the fan. Do more work with the fan, and less power is available to move the truck.

In the real world, in the summer (which begins in May around here) I make a particular hundred mile commute (Phoenix to/from Payson, via SR87) several times a week. This route takes me over several grades. I see a significant difference when pulling those grades when I mess with the fan clutch. On one particular grade (Mt Ord, southbound) I was able to maintain a speed of 62 mph with a particular clutch mod, and now that I have altered that mod with a significantly higher CST oil I have slowed to 47 mph on the same grade in the same conditions. Literally from one day to the next, and consistently. My work partner (@richardlillard1) has also seen the same effect. We both chased the cause of this for months, finally realizing it was the fan clutch mods that were causing the 'loss of power' we were concerned about. Since we hypothesized that modding the clutch was the cause of the power loss we have both tested the theory by swapping in different clutches on that drive, and confirmed that the fan clutch was the culprit. The reason we have stuck with the heavily modded clutches is 40 degree air conditioning and 195 degree engine temps in 100+ degree ambient temperature on that same hill climb. In Arizona, the trade-off of power for cooling capacity is well worth it.

EDIT- I should add that the extremes that I have gone to in modding my clutch were not only, or even primarily, about cooling at highway speeds. My truck spends hours at a time several days a week idling or moving less than 10 mph. Moving more air at an idle is the primary reason that I have gone to extremes, and the mods don't end with the clutch. For instance, air flow has been channeled to force it to go only though the condenser and radiator, rather than around those components, and currently there is an electric fan on the condenser. However, the most significant drain on horsepower was traced back to the fan clutch specifically.
 
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richardlillard1

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Alright, thanks for the explanation. How would you go about heating the spring up and setting the valve to a specific temp?

The spring needs to be heated somehow. I use a heat gun at the shop, but in the past I’ve used lighters with good success. Don’t hold it too close or in the same spot, but move it around and it will heat the spring enough to open the valve.
 
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Alright, thanks for the explanation. How would you go about heating the spring up and setting the valve to a specific temp?
The spring needs to be heated somehow. I use a heat gun at the shop, but in the past I’ve used lighters with good success. Don’t hold it too close or in the same spot, but move it around and it will heat the spring enough to open the valve.
Richard probably missed the second question. The answer is you need to have a thermometer on the spring that can instantly react to temperature changes. A thermocouple works best, however I use an instant-read infrared thermometer.
 
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I opened up my Eaton clutch, drained and used 10K fluid...works like new in my 96 LX-450

244.JPG
 
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Modding the clutch usually involves lowering the temperature at which it engages and using a higher CST oil (thicker), which makes it pull more air, in essence spin faster at a given RPM. Logically, both of these effects are going to use more energy, or horsepower. There really is no argument against this. To do more work requires more power. That power is finite, so the horsepower left over for locomotion is reduced. I suppose one could say that total horsepower is not reduced, which is technically true, but some of it is used to power the fan. Do more work with the fan, and less power is available to move the truck.

In the real world, in the summer (which begins in May around here) I make a particular hundred mile commute (Phoenix to/from Payson, via SR87) several times a week. This route takes me over several grades. I see a significant difference when pulling those grades when I mess with the fan clutch. On one particular grade (Mt Ord, southbound) I was able to maintain a speed of 62 mph with a particular clutch mod, and now that I have altered that mod with a significantly higher CST oil I have slowed to 47 mph on the same grade in the same conditions. Literally from one day to the next, and consistently. My work partner (@richardlillard1) has also seen the same effect. We both chased the cause of this for months, finally realizing it was the fan clutch mods that were causing the 'loss of power' we were concerned about. Since we hypothesized that modding the clutch was the cause of the power loss we have both tested the theory by swapping in different clutches on that drive, and confirmed that the fan clutch was the culprit. The reason we have stuck with the heavily modded clutches is 40 degree air conditioning and 195 degree engine temps in 100+ degree ambient temperature on that same hill climb. In Arizona, the trade-off of power for cooling capacity is well worth it.

EDIT- I should add that the extremes that I have gone to in modding my clutch were not only, or even primarily, about cooling at highway speeds. My truck spends hours at a time several days a week idling or moving less than 10 mph. Moving more air at an idle is the primary reason that I have gone to extremes, and the mods don't end with the clutch. For instance, air flow has been channeled to force it to go only though the condenser and radiator, rather than around those components, and currently there is an electric fan on the condenser. However, the most significant drain on horsepower was traced back to the fan clutch specifically.


That was a thorough explanation, thanks for taking the time to explain and for sharing the knowledge. This job seems to be more of an intricate endeavor but I understand the pros vs cons now. Very interesting to read how much performance the clutch took from the engine though. This is great info!
 

Bambusiero

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Hi @richardlillard1 and @-Spike- , when you guys tune the fan clutch opening temperature, how "open" is open? Asking because the Eaton clutch has a gradual opening, a so you could target a wide range of behavior just by ones definition of "open". (and there are 2 openings, each offset from the other. Tune left or right window? Here are 3 photos I took long ago when I did this. Do you just grab the bimetal spring and twist/bend it to a new set point?

Hmm...and the windows on my Eaton are quite a different shape than @woodsman 44 - well, I think they are both Eatons.
FluidClutchThermostat_163F.jpg


FluidClutchThermostat_181F.jpg


FluidClutchThermostat_201F.jpg
 
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Hi @richardlillard1 and @-Spike- , when you guys tune the fan clutch opening temperature, how "open" is open? Asking because the Eaton clutch has a gradual opening, a so you could target a wide range of behavior just by ones definition of "open". (and there are 2 openings, each offset from the other. Tune left or right window? Here are 3 photos I took long ago when I did this. Do you just grab the bimetal spring and twist/bend it to a new set point?

Hmm...and the windows on my Eaton are quite a different shape than @woodsman 44 - well, I think they are both Eatons.
View attachment 2355180

View attachment 2355181

View attachment 2355182


Looks to be an Eaton, same as mine....no need to tune Eaton just heat on low in oven for mabey 30 mins (take off orange oring/seal) then take out and tip halves up and let it drain overnight, then use heat gun on front circle spring and add small bolt when slot opens up and fill......you can see bolt in my pic of it holding open the slot...fill up in open slot

I used 10Kwt. fluid, dont go more than 15K wt. fluid for Eaton
 
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richardlillard1

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Richard probably missed the second question. The answer is you need to have a thermometer on the spring that can instantly react to temperature changes. A thermocouple works best, however I use an instant-read infrared thermometer.

I had missed that. The thermocouple we use at the shop has done dozens (probably hundreds) of clutches by this point. Haven’t tried the infrared thermometer, but I’m sure it gives good data.

Hi @richardlillard1 and @-Spike- , when you guys tune the fan clutch opening temperature, how "open" is open? Asking because the Eaton clutch has a gradual opening, a so you could target a wide range of behavior just by ones definition of "open". (and there are 2 openings, each offset from the other. Tune left or right window? Here are 3 photos I took long ago when I did this. Do you just grab the bimetal spring and twist/bend it to a new set point?

Hmm...and the windows on my Eaton are quite a different shape than @woodsman 44 - well, I think they are both Eatons.
View attachment 2355180

View attachment 2355181

View attachment 2355182

When I set the opening temperature on any clutch I look for the first opening of the valve, whichever window that happens to be. Aisins are a lot easier in this regard, but the principle is constant regardless of Eaton/Aisin.

I always refer back to Kevin’s insight with regards to opening of the valve; the best results he found are ~120°F on the first opening of and ~200°F at full open. I’ve found getting the opening temp to be more critical than the full open, but check both anyway. This also gives you an indication as to whether the valve has any sort of hiccups or other weirdness.

Looks to be an Eaton, same as mine....no need to tune Eaton just heat on low in oven for mabey 30 mins (take off orange oring/seal) then take out and tip halves up and let it drain overnight, then use heat gun on front circle spring and add small bolt when slot opens up and fill......you can see bolt in my pic of it holding open the slot...fill up in open slot

I used 10Kwt. fluid, dont go more than 15K wt. fluid for Eaton

You can get away with a lot more in an Eaton, a couple have run 30-33k long-term. But the weather in Phoenix might warrant a different desired outcome than northern California.

I agree, the Eaton generally doesn’t need to be adjusted. But have also found that some tweaking can get a better end result.
 
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Like @JeepinPete said, if you weren't overheating before and the fan clutch is adequate for your usage, I see no need to replace it.

My truck was getting overwhelmed on the mountain passes in summertime, so I modded my black fan clutch with 20k cst and it still didn't pull enough air. I think the thing was just worn out. My truck has 330k. I eventually got the wits' end fan clutch and it works like it should. But it was only replacing the radiator (TYC 1918) and fan clutch together that really brought my truck back to what I would consider happy temps on the mountain passes.
 

Bambusiero

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When I set the opening temperature on any clutch I look for the first opening of the valve, whichever window that happens to be... ~120°F on the first opening of and ~200°F at full open. I’ve found getting the opening temp to be more critical than the full open, but check both anyway.
You can get away with a lot more in an Eaton, a couple have run 30-33k long-term. But the Eaton generally doesn’t need to be adjusted. But have also found that some tweaking can get a better end result.

OK, gotcha, thanks for the tips.
 
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I would replace the fan clutch if you plan to keep the truck more than a couple more years.
I did a lot of work on my cooling system, including draining and replacing the fluid in my fan clutch (and every part and hose you can think of in the entire system), and I still was hitting close to 220* on long hot climbs while wheeling. I just bought a blue hub clutch and replaced the fluid before I even installed it, and now I rarely get above 200*. I just think things only work so long, including the fan clutch.
So, I agree with @jonheld and @flintknapper, just replace the fan clutch and inspect the fan closely. I'm actually just going to replace my fan sometime in the next few months. I plan to keep my truck another ten years, and I don't think it's reasonable to expect the plastic fan to last 35 years. Just my two cents. Good luck.
 

flintknapper

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I'm actually just going to replace my fan sometime in the next few months. I plan to keep my truck another ten years, and I don't think it's reasonable to expect the plastic fan to last 35 years. Just my two cents. Good luck.

^^^^^

Smart of you. I'm not advocating replacing parts that are still good, but this is an inexpensive item ($30.00) and well worth the preventative measure and peace of mind. Plastic and Rubber parts tend to have a useful 'life span'....after which they degrade.
 
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I did it because I was changing the front main seal and oil pump seal.

For the price you might as well do the front main seal, oil pump seal, water pump, clutch, fan blade, and I also changed the radiator to aluminum while I had everything apart. I also did both radiator hoses. Once you've started, you might as well replace everything, no point in going in there twice.

I tow at high elevation and didn't want my cooling system going down in the middle of nowhere with a camper on the back. I'm sure certain things could last longer, but this truck is 23 years old and I personally haven't been taking care of it the last 23 years.
 
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I did it because I was changing the front main seal and oil pump seal.

For the price you might as well do the front main seal, oil pump seal, water pump, clutch, fan blade, and I also changed the radiator to aluminum while I had everything apart. I also did both radiator hoses. Once you've started, you might as well replace everything, no point in going in there twice.

I tow at high elevation and didn't want my cooling system going down in the middle of nowhere with a camper on the back. I'm sure certain things could last longer, but this truck is 23 years old and I personally haven't been taking care of it the last 23 years.


That is exactly what I did with the exception of the aluminum radiator, installed a Denso one...$400 for a TRAD seems a little steep at the moment for me. Shout out to Giuseppe from Wits End, best kits for oil pump cover, front main seal etc.

I definitely don't regret replacing pretty much the whole cooling system + the seals. Temps on the highway now are around 148˚F and 160˚F in the city, 2˚-4˚F cooler than with the old system. Honestly, replacing the whole cooling system for around $250 or even less by doing it ourselves is the best choice. One, the rig runs cooler and two, avoid that head gasket job at a earlier stage.
 
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Temps on the highway now are around 148˚C and 160˚ in the city
Somehow I think you've made an error in your temperature readings.
148C=298F - The ECU will cut off the AC compressor around 220F to reduce load on the engine.
160C=320F - Your motor has liquefied.

If you meant to say F, then 148F and 160F is below normal operating temperature.
 

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