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Unread 05-21-2013, 11:11 AM   #1
RowJ
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Fan Clutch Question

I can move it but no free spin from fan when shut down.
I understand this means slower warm ups but doesn't it also mean max cooling... all the time?

Would a properly functioning viscous fan clutch serve me better in solving my primary issue .........
overheating at interstate speeds on 85*+ days?
With A/C off, TJ runs to right of 0 in 210*.
With A/C on...just slowly climbs (to red line) or till I stop using.

RJ

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Unread 05-21-2013, 11:17 AM   #2
TheBoogieman
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"Locked in"?
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Unread 05-21-2013, 11:19 AM   #3
RowJ
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Locked in = Appears to be matching rpm w/ engine .... and rolled up newspaper on fan blades can't slow it any.
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Unread 05-21-2013, 11:24 AM   #4
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Quote:
Originally Posted by RowJ View Post
Locked in = Appears to be matching rpm w/ engine .... and rolled up newspaper on fan blades can't slow it any.
You can't spin it at all by hand with the engine cold?
To test whether or not your fan clutch needs to be replaced, simply spin your Jeep's fan by hand while the engine is cold and if it spins freely 5 rotations or more, it will need to be replaced.

When working properly, the fan clutch will react to the heat discharging from you radiator by spinning faster or slower depending on the cooling needs of your engine.
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Unread 05-21-2013, 11:29 AM   #5
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Assuming the passages in the block are not as they restrict the flow of coolant there are only three things that could make the engine over heat. Clogged up radiator, bad water pump or fan clutch. Start with the easiest. How does the inside of the radiator look? Remove cap and describe. Then with a warmed up engine running at around 1500 RPM can you see coolant flowing in the radiator with the cap removed? If the radiator looks clean and not plugged up and you can see coolant flowing freely with the radiator cap removed, then the fan clutch must be going out.
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Unread 05-21-2013, 11:34 AM   #6
Jonny Jeep
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If you think your fan may be a problem there is a test procedure in the cooling section of the FSM (linked in my sig if you don't have one). When the engine is cool you should be able to turn the fan but it shouldn't freewheel. If it is locked up it will be roaring when the engine is running, and it wouldn't cause overheating if it's locked up.
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Unread 05-21-2013, 12:15 PM   #7
RowJ
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Quote:
Originally Posted by TheBoogieman View Post
You can't spin it at all by hand with the engine cold?....
As mentioned, I can turn it, but no free spin at all after I release it.
Quote:
Originally Posted by Jonny Jeep View Post
..... If it is locked up it will be roaring when the engine is running, and it wouldn't cause overheating if it's locked up.
Not roaring. And Radiator, pump, T-stat, Cap, etc.... all were factory, and all were replaced 30 months ago.
My problem is not "no viscous action" it is too much, if anything.
But if it's working near right, why doesn't it "roar" and cool things down, when I get climbing to the red line??

RJ
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Unread 05-21-2013, 12:54 PM   #8
freeskier93
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Quote:
Originally Posted by Jonny Jeep View Post
If you think your fan may be a problem there is a test procedure in the cooling section of the FSM (linked in my sig if you don't have one). When the engine is cool you should be able to turn the fan but it shouldn't freewheel. If it is locked up it will be roaring when the engine is running, and it wouldn't cause overheating if it's locked up.
A locked up fan clutch could theoretically cause higher temps, especially if the rest of the cooling system is aging and maybe not as efficient. On the highway the fan should be free wheeling as the air being pushed through the radiator from moving is more than the fan could ever pull. If the fan is locked up then it is causing unnecessary load on the engine, and it's a rather large load.
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Unread 05-21-2013, 01:55 PM   #9
RowJ
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Originally Posted by freeskier93 View Post
A locked up fan clutch could theoretically cause higher temps..... On the highway.... the air being pushed through the radiator is more than the fan could ever pull. If the fan is locked up then it is causing unnecessary load on the engine, and it's a rather large load.
Wondered about that. Seemed possible but could not reason it out.
Not sure if your making reasonable assumtions, guessing or speaking from engineering background but .....
I'm frustrated enough that I'm buying a new fan clutch.

RJ
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Unread 05-21-2013, 03:21 PM   #10
TheBoogieman
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I got lucky when my fan clutch went bad.It squealed like a stuck pig.My XJ runs a little hot,but they have an electric fan as well as the other.My e fan wasn't cutting on to cool it.Jonny Jeep knows his stuff even if he spells his first name wrong.
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Unread 05-22-2013, 07:22 AM   #11
JBTJ
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Quote:
Originally Posted by RowJ View Post
Wondered about that.Seemed possible but could not reason it out.
Not sure if your making reasonable assumtions, guessing or speaking from engineering background but .....
I'm frustrated enough that I'm buying a new fan clutch.

If this line of storms ever moves on (the one that hit OKC area with tornados for the last three days), I'll test your hypothesis.
We had 3 " rain last week and 3" more between yesterday and today!
Guess I should just be thankful for no tornados near here!

RJ
What did you find out?
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Unread 05-22-2013, 08:26 AM   #12
RowJ
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Quote:
Originally Posted by JBTJ View Post
What did you find out?
Installed new fan clutch last night in my garage.
-On start up.... idle was much quieter than has been
-On road, warm up was definitely faster and engine made less noise.
-Throttle appeared to be more responsive (as in less engine drag)
The last is subjective so.......?

Ultimate test will be coolant temps this weekend - 200 mile RT on hwy (going to Bridgeport JB)
But appears obvious that my fan clutch was gradually locking up.
Situation snuck up on me so I did not notice more noise or drag.
Fan clutch would still pass the spin test but was much harder to rotate than the newer viscous clutch.

Appears 'FreeSkier' was correct in post #8, about a locked up fan = extra load on the engine.
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Unread 05-22-2013, 09:14 AM   #13
JBTJ
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Quote:
Originally Posted by RowJ View Post
Installed new fan clutch last night in my garage.
-On start up.... idle was much quieter than has been
-On road, warm up was definitely faster and engine made less noise.
-Throttle appeared to be more responsive (as in less engine drag)
The last is subjective so.......?

Ultimate test will be coolant temps this weekend - 200 mile RT on hwy (going to Bridgeport JB)
But appears obvious that my fan clutch was gradually locking up.
Situation snuck up on me so I did not notice more noise or drag.
Fan clutch would still pass the spin test but was much harder to rotate than the newer viscous clutch.

Appears 'FreeSkier' was correct in post #8, about a locked up fan = extra load on the engine.
Based on differences so far, I hope to see my over heating at hwy speeds greatly reduced.
Will report back after weekend.
Good, I'm glad you got it fixed. That was probably your problem. As I said earlier, it has to be one or more of the three items I mentioned.
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Unread 05-27-2013, 09:22 AM   #14
RowJ
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Follow up ........
200 miles trip w/ temps up to 88*.
Coolant settles in at just under 210* @ 60 mph.
With A/c on it climbs to right of 0 in 210, but does level off!!
Also gained 1.1 mpg over previous best trip mileage.
Got 16.1 mpg, driving 60 mph and top off, with a 5-7 kt headwind.

$40.00 for new fan clutch appears to have been a great investment!

RJ
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