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New Fan Clutch Sound.

842 views 8 replies 4 participants last post by  mercron 
#1 · (Edited)
Hello.

The fan clutch failed and slipped badly that coolant temp reaches +100C on high way before it connects sometimes for just a little while then slips back again.

I replaced it with another OEM Behr one that comes with a yellow tag. Temps now stay 82-85C highway. The coolant t-stat is rated 82C.

Is the fan suppose to be audible on a highway at 3000 RPM, 30-35C ambient with A/C on? I tried going 4500 RPM and noticed temp starting to rise to +95C at 35C ambient, which I believe means the fan clutch safe slips at about the right RPM speeds (?).

Before replacement, it used to be completely disconnected and quiet until temp reaches like 95C even at +35C ambient, connects to cool until 85C then disconnects. When it disconnected, it got too quiet I could only hear the sound of the engine, as if there is no engine fan at all. Or is the fan clutch suppose to keep the temp more stable than that?

I was happy at the sound before the old fan clutch slipped so badly, but had doubts about the temps.

Thoughts?
 
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#2 ·
At highway speeds, the viscous fan should just be along for the ride. The purpose of the clutch is to allow the fan to " float" at speed and not be a parasitic drain on the motor. Before you replaced the clutch, did you do the fan test? What were your "in town" operating temps running before you replaced the clutch?
 
#3 ·
Parasitic at what speeds are you asking? I know the clutch tightens more at radiator's high temps (I think above 98C), but should the clutch slip at lower temps too or just at the safe slip RPM speed? Winter is coming and we will see 25C ambient and a little lower (if we're lucky, haha). Should the clutch loosen up and make no fan sound then?

I tested the old clutch myself. I waited for coolant temp to go ~100C and observed the fan with an open hood and it refused to increase speed at all as I revved the engine. I turned off the engine, on again after like a minute to make sure hot air from the radiator accumulates, and re-tested. This time the fan increased speed as I revved to ~2000 RPM but just momentarily and it slipped again. Coolant temp was +100C then. Same thing happened in a highway speed while coolant temp went +100C.

In town operating temps stay about 95C with the A/C on at ambient +40C most of the time and goes to almost 100C with heavy traffic and I start the aux fans at high speed then it easily goes down to 90C or less. Is this bad? (I installed a manual high speed fan switch, by the way). I'm perfectly fine with that, by the way. My problem was only on highways temp wise which now is solved, and got replaced with doubts about normal highways fan sound before the safe slip RPM limit.
 
#4 ·
Ah, I hope I didn't make big deal of it giving the subject more than it deserves.

The fan clutch is not stuck and I can move it with my hand, but there is torque to it. It does not freely spin nor pull the belt with it.
 
#6 ·
If your clutch is operating as it should, you should hear it cut out and in . . . usually in the 3000-3500rpm range
This clears half of my doubts. Does that mean the clutch never slips depending on temp alone; e.g. if ambient is 20C and coolant temp is 82C at lower RPM's? For the last year, I've been driving at highways not even touching the 3000 RPM mark. It would be nice to have quieter engine in the winter and lower gas consumption while coolant temp is still low and safe.
 
#7 · (Edited)
The fan clutch is operated by a bimetallic spring, allowing fluid to pass from one passage to another. If the spring does not get enough heat to flex, the fan will also not engage.

In other words, the clutch will only engage the fan when needed.

Some people on this board think they can outsmart a multibillion dollar engineering company by adding electric fans and/or removing the fan clutch altogether when the stock piece works just fine. Yes, all things wear out with time and that is when you replace them with a identical stock unit. Other than that, leave it alone.

What is often overlooked is lack of airflow hitting the fan clutch. Therefore, it is always good practice to pressure wash the condenser and radiator fins and remove, clean, and reinstall the aux fan shroud since it acts as a vacuum cleaner bag. In dusty climates, the should probably be done at least every couple of years. It makes a noticeable improvement

One more thing, a radiator with a cold center spot can also cause the fan clutch to not engage
 
#8 ·
Clutch driven fans give better air pressure anyway.

I guess things are fine then. I noticed that the engine fan does not sound as noisy at +120kmph and engine sound takes over. I think if the clutch was stuck or heavy more than factory ready settings, it would sounds so loud at that speed and engine torque would suffer, but it does not.
 
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