How to tell the radiator fan clutch, aka liquid coupling, is good or bad? (1 Viewer)

[AFei]

It seems that my coolant temperature runs higher than average in Phoenix' hot summer. If I didn't remember it wrong, it's at around 196 degree on highway speed, but could bump to 215 degree on slow hill climb or stop-go traffic.

Radiator is new Denso. Changed the thermostat last night. Now trying to make sure the cooling fan working as expected. How could I tell if the fan clutch is in good working condition? I can turn the fan freely when engine is cool. but not quite sure if the clutch will engage/lock when needed

Searched and read some posts, and here is what I learned so far:

1. When engine is hot, it should feel some resistance when trying to turn the fan by hand, which means the clutch is engaged/locked at some degree
2. It's very loud, like airplane, when the clutch is locked.

Both ways sounds like depending on personal feeling. Is there any practical way to actually test/measure the clutch?

Also, if there any certain temperature that the clutch must be engaged/locked?

Thanks!

 

[KliersLC]

Well, I am sure there is some kind of technical way, but this has always worked for me. Keep in mind that it isn't the "most" safe way, but it is mostly safe

1. Get it nice and hot, pop the hood, and with a welding glove on, stick your hand against the fan with an open palm so the blades skip off of your hand. If the fan beats the heck out of your hand, when you apply pressure, it is working. If the fan slows down significantly with minimal effort on your part, it needs work.

2. Same as above but use a broom handle.

However, based on your described symptoms, you probably need a new fan clutch or to change out your fan clutch fluid (if tedious tinkering is your thing)

 

[JunkCrzr89]

Start at 3:00 to see diagnosis procedures

 

[AFei]

Well, I am sure there is some kind of technical way, but this has always worked for me. Keep in mind that it isn't the "most" safe way, but it is mostly safe

1. Get it nice and hot, pop the hood, and with a welding glove on, stick your hand against the fan with an open palm so the blades skip off of your hand. If the fan beats the heck out of your hand, when you apply pressure, it is working. If the fan slows down significantly with minimal effort on your part, it needs work.

2. Same as above but use a broom handle.

However, based on your described symptoms, you probably need a new fan clutch or to change out your fan clutch fluid (if tedious tinkering is your thing)

hmmm, let me think how to do this.... May skip 1 but try 2.

 

[AFei]

Start at 3:00 to see diagnosis procedures

Perfectly. Will give it in this hot afternoon...

 

[gregnash]

hmmm, let me think how to do this.... May skip 1 but try 2.

Most people will take a magazine or newspaper and roll it up and stick that in the blades. If the fan clutch is fully engaged it will just shred the end of the paper without damaging anything.

 

[AFei]

So basically summary the recommendations from @KliersLC , @JunkCrzr89 and @gregnash , I will perform the following test steps this hot afternoon:

1. When engine is COLD and OFF, try to spin the fan by hand. It should spin easily but only a little, like no more than 1.5 turns.
2. When engine is COLD, start the engine. Fan should roar at very beginning and then quiet down. I love this roaring sound BTW.
3. Fan speed should response corresponding to the throttle.
4. After the fan quiets down from the engine cold start, roll a paper stick by magazine or newspaper. Try to bush this paper stick into the fan, and it should be able to stop the fan, as the clutch should not have locked yet.
5. Do a test drive to bring the engine to operating temperature (assuming the coolant should be over 180 degree when the thermostat opens to allow coolant flowing into radiator).
6. Do the same test as step 4. This time, the paper stick should NOT be able to stop the fan, and it will just shred the end of paper stick., since the fan clutch should be fully engaged at this time.
   • CAUTION: DO NOT PUSH ANY PART OF YOUR BODY INTO THE FAN; DO NOT LET YOUR LONG HAIR GET INTO THE FAN .
7. Stop and park the car in a safe place, and then shut the engine off. Try to spin the fan by hand. This time it should be very hard to move it. Watch and don't touch any part of the engine or radiator. It can be very hot!

Just hope it can pass....

 

[flintknapper]

Most people will take a magazine or newspaper and roll it up and stick that in the blades. If the fan clutch is fully engaged it will just shred the end of the paper without damaging anything.

^^^^

Yes, do this. If you don't have a Cat.

If you have a cat, then a cat's tail will work too. Just kidding, I like cats.

 

[medtro]

^^^^

Yes, do this. If you don't have a Cat.

If you have a cat, then a cat's tail will work too. Just kidding, I like cats.

My neighbor cats like doing this test

 

[peacesells63]

Sticking anything in the fan of a running truck is a terrible idea and doesn’t mean much. First of all, look at the clutch and inspect for any signs of fluid leaks. If there are any, that’s the problem and you need a new clutch. Check for play also.

Just spend the $70 on an Aisin fan clutch from rock auto, then you’ll have the old one to take apart and play with. Can’t tell you how many times I have answered this question for people, every one had been fixed with a new fan clutch.

 

[DuckLN]

Sticking anything in the fan of a running truck is a terrible idea and doesn’t mean much. First of all, look at the clutch and inspect for any signs of fluid leaks. If there are any, that’s the problem and you need a new clutch. Check for play also.

Just spend the $70 on an Aisin fan clutch from rock auto, then you’ll have the old one to take apart and play with. Can’t tell you how many times I have answered this question for people, every one had been fixed with a new fan clutch.

You haven’t addressed the question

 

[peacesells63]

You haven’t addressed the question

?

would you stick your hand in a running fan before you would check for leaks and play?

 

[AFei]

So basically summary the recommendations from @KliersLC , @JunkCrzr89 and @gregnash , I will perform the following test steps this hot afternoon:

1. When engine is COLD and OFF, try to spin the fan by hand. It should spin easily but only a little, like no more than 1.5 turns.
2. When engine is COLD, start the engine. Fan should roar at very beginning and then quiet down. I love this roaring sound BTW.
3. Fan speed should response corresponding to the throttle.
4. After the fan quiets down from the engine cold start, roll a paper stick by magazine or newspaper. Try to bush this paper stick into the fan, and it should be able to stop the fan, as the clutch should not have locked yet.
5. Do a test drive to bring the engine to operating temperature (assuming the coolant should be over 180 degree when the thermostat opens to allow coolant flowing into radiator).
6. Do the same test as step 4. This time, the paper stick should NOT be able to stop the fan, and it will just shred the end of paper stick., since the fan clutch should be fully engaged at this time.
   • CAUTION: DO NOT PUSH ANY PART OF YOUR BODY INTO THE FAN; DO NOT LET YOUR LONG HAIR GET INTO THE FAN .
7. Stop and park the car in a safe place, and then shut the engine off. Try to spin the fan by hand. This time it should be very hard to move it. Watch and don't touch any part of the engine or radiator. It can be very hot!

Just hope it can pass....

Just performed the tests yesterday, and all passed. The fan clutch worked exactly as the expectation. A side note: The clutch did lock up slightly after the coolant reached 185 degree.

Under the open air temperature at 100 degree, the coolant ran at about 188~195 degree on highway speed during the short test drive. Idle with AC on, the coolant temperature slowly climbed over 200.

With the new radiator, new thermostat, and working clutch, now I have to worry about what could be the next culprit of higher than average coolant temperature?

 

[AFei]

Sticking anything in the fan of a running truck is a terrible idea and doesn’t mean much. First of all, look at the clutch and inspect for any signs of fluid leaks. If there are any, that’s the problem and you need a new clutch. Check for play also.

Visual checking didn't see any fluid leaking. Not sure how to check the play, but the fan didn't wobble.

would you stick your hand in a running fan before you would check for leaks and play?

Agreed with you that it's not safe to stick hand in a running fan. However, with the paper stick rolled from newspaper, it could stop the fan from running before the clutch locked. Once the clutch locked, you could feel it immediately when the paper touched the flan blade as it just ran so fast and felt uncomfortably to keep pushing the paper.

 

[gregnash]

Ok so what are you seeing as temps now? I guess what I am failing to see is what is making you feel like the temps are higher than they should be? Normal operating temp should range up to about 220* if I remember correctly, especially in hot areas where you have slow crawls that may not be pulling adequate air across the radiator to cool the system. There could potentially still be bubbles in your system that may be stuck near or at the thermostat causing it to read incorrectly.

I have a ScanGauge connected to my truck and once warmed up I will see close to 200* on hill climbs up to Lake Tahoe (averaging about 50-55mph on the climb) in normal weather. If you are seeing your temps climb to 215 on a regular basis and staying there then I would see about maybe having your system flushed and new stuff added.

When you did the rad/t-stat/etc. replacement did you replace with Toyota OE stuff (or at least high quality ASIAN vehicle stuff)? When was the last time the TB/WP was done?

 

[peacesells63]

Just performed the tests yesterday, and all passed. The fan clutch worked exactly as the expectation. A side note: The clutch did lock up slightly after the coolant reached 185 degree.

Under the open air temperature at 100 degree, the coolant ran at about 188~195 degree on highway speed during the short test drive. Idle with AC on, the coolant temperature slowly climbed over 200.

With the new radiator, new thermostat, and working clutch, now I have to worry about what could be the next culprit of higher than average coolant temperature?

Any of those tests will only tell you if there is a complete (100%) failure of the clutch. I have only seen that once on a 100 series, and it was blaringly obvious by the grinding noise it was making. That fan would have shredded a phone book before stopping.

If you want to do a more scientific test on the fan, clutch send me a pm with your number and I will give you a call. It takes 3-4 hours, you’ll need 2 digital thermometers, a stove, a pan of water, a laptop with excel, and a big fan or portable swamp cooler. Also, you will have to remove the fan clutch at least once.

Over 200 is not necessarily hot. Did you recently get an obd2 scanner? I got obsessed with temps when I first got one, went through the cooling system on 2 trucks afterwards with no change.

Are you seeing these temps with ac on or off? The temps fluctuate a lot on these trucks, and really any vehicle in the summer for that matter. If you are seeing temps above 215 in 100 degree weather with the ac off, I’d be worried. 200-215 is normal. Once you get to 220, start to worry a little bit.

Next time it’s 115, let to idle in the driveway for 30 mins with the ac on outside air high and see what it balances out at. If it gets to 220, order a new fan clutch.

All signs you have posted so far = weak fan clutch

 

[AFei]

When you did the rad/t-stat/etc. replacement did you replace with Toyota OE stuff (or at least high quality ASIAN vehicle stuff)? When was the last time the TB/WP was done?

TB/WP was done with Aisin parts 2 years ago at 199K. Denso radiator installed last month. Toyota t-stat installed 2 days ago (old none-oe one was about 30K miles old).

I just started watching the coolant temperature recently, after the radiator popped out the top seal on my trip to MD. Comparing to my other MDX, I noticed the LX tended to run at about 10~15 degree higher coolant temperature under similar weather, which concerned me . I saw those close to 220 temperature during 110+ degree days, maybe that's why. Did see 220+ several times but it was under 115+ degree with AC on 4L climbing a steep slope.

Any of those tests will only tell you if there is a complete (100%) failure of the clutch

All signs you have posted so far = weak fan clutch

I believe you are right and all these tests could only conclude a working but may not fully functioning (therefore weak) clutch.

Guess I will keep close watching of the cooling performance during the July 4th long weekend trip, and would most likely replace the clutch after that.

If you want to do a more scientific test on the fan, clutch send me a pm with your number and I will give you a call. It takes 3-4 hours, you’ll need 2 digital thermometers, a stove, a pan of water, a laptop with excel, and a big fan or portable swamp cooler. Also, you will have to remove the fan clutch at least once.

Sounds like a fun scientific experiment. Since the clutch has to be removed, I will probably just replace it with new one and leave the test to my daughter

 

[KliersLC]

So, I just noticed that are in Phoenix. That changes things a little. There is a lot of time and effort in the 80 series forums regarding modifying the fan clutch in order to cool the trucks down. This involves filling the clutch with a higher viscosity fluid, or buying one that has already been modified. I'll dig around and see if they have modified one for the 100.

 

[peacesells63]

TB/WP was done with Aisin parts 2 years ago at 199K. Denso radiator installed last month. Toyota t-stat installed 2 days ago (old none-oe one was about 30K miles old).

I just started watching the coolant temperature recently, after the radiator popped out the top seal on my trip to MD. Comparing to my other MDX, I noticed the LX tended to run at about 10~15 degree higher coolant temperature under similar weather, which concerned me . I saw those close to 220 temperature during 110+ degree days, maybe that's why. Did see 220+ several times but it was under 115+ degree with AC on 4L climbing a steep slope.




I believe you are right and all these tests could only conclude a working but may not fully functioning (therefore weak) clutch.

Guess I will keep close watching of the cooling performance during the July 4th long weekend trip, and would most likely replace the clutch after that.


Sounds like a fun scientific experiment. Since the clutch has to be removed, I will probably just replace it with new one and leave the test to my daughter

With that info, pretty safe to safe to say its a fan clutch.

Last guy I helped out kept having to stop on a trail when it was about 95 out because the truck was boiling over. He already paid something like $1700 to bell lexus for a radiator, tstat, cooling flush, hoses and water pump. 3 separate trips to the dealer, and the fan clutch fixed his issue. he was hitting 235 when it would boil over, and said youd never know there was a problem any other time.

Yep, its definitely a process, but I was verifying a few 80 series black hub (obsolete) fan clutches were good, so it was worth it.

 

[peacesells63]

So, I just noticed that are in Phoenix. That changes things a little. There is a lot of time and effort in the 80 series forums regarding modifying the fan clutch in order to cool the trucks down. This involves filling the clutch with a higher viscosity fluid, or buying one that has already been modified. I'll dig around and see if they have modified one for the 100.

I'm sure someone mods 100 series, but IMO its not necessary on the 100 like it is the 80. The cooling system is way larger and radiator has much more surface area than the 80 series, so the stock fan oil works much better than the stock oil in a blue hub 80 series fan. 80 series is a fairly fine line between the fan engaging on the highway and running hot on the trail.