Hayden clutch function question

Caddis · **Posted:** Mon Aug 06, 2012 11:59 am

For those of you with the Hayden 2905 fan. How much does it seem to run with average driving?
I just installed it yesterday along with a replacement OEM thermostat, and it seems to me that the fan is running almost constantly, from the moment I've started it up cold a couple of times. I know when it's not engaged there will always be a little air movement from the fan, but it sure seems like it's really pushing all the time. Is this normal or do the t-stat and fan just need to "work out the kinks"?

papaindigo · **Posted:** Mon Aug 06, 2012 12:16 pm

I'm currently running, relatively recently, the Hayden with the 11 blade nylon fan. Before that I ran Kap's fixed fan for about 1200 miles. Before that I had the stock metal fan and fan clutch. In reverse order:
1. I don't know if the stock metal fan ever engaged on my current or former 05. The former's temp gauge never got abover vertical. My current one did but that was before I had the temp gauge correctly flashed. Bottom line I don't think this fan ever "engaged". It did spin all the time but I don't really recall how much.
2. the fixed fan spun wide open, same as a clutch fan engaged, and can best be described, with the hood open, moving a vast amount of air at high speed.
3. the Hayden with nylon fan spins fast enough that I cannot see the individual blades but when not engaged (neutral) it's not moving much air, compaired to 2 above think a light draft vs a howling gale.

A clutched fan will spin constantly but how fast is going to depend on the friction that's inherient in the assembly and possibly the weight of the fan. I did attempt to manually, no gauge, compare the friction between the OEM clutch and the Hayden and there was not a significant difference.

Bottom line is constant spin is fine. See above comment on air movement at normal spin in "neutral" vs locked up.

Caddis · **Posted:** Mon Aug 06, 2012 12:23 pm

Hmmm, so maybe since it's going to be a little hotter here this afternoon, I should go drive around with the AC cranked up and see if I can warm the engine up a little more and determine if the clutch engages then and creates more air flow than what I'm experiencing right now.

ChooChooman74 · **Posted:** Mon Aug 06, 2012 12:36 pm

When that fan is engaged fully, you will hear it. I have only heard mine a few times since installing it. Big test is next weekend when I go camping.

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Rabert · **Posted:** Mon Aug 06, 2012 1:21 pm

With the weather here in the Fort worth, TX area I can tell you I hear it after taking off from a stop sign then it fades away. I do not hear it so much going up a hill or prolonged idle. It seems that as long as air is moving across the radiator I do not hear it. I have the Hayden clutch with metal fan and a relatively new Thermostat. But, since installing it I have yet to see the needle even get close to the vertical position, stays just to the left even in the 100+ weather we are having, with the AC blowing/up hill/down hill/forwards/backwards.

naturist · **Posted:** Mon Aug 06, 2012 7:17 pm

I haven't noticed it running unless I am towing and climbing a big hill in hot weather, just like the stock clutch is supposed to do.

On the other hand, it is supposed to engage at 170˚F, which is 20˚ cooler than the thermostat is supposed to hold the engine, so I imagine that simply sitting in the engine bay, bolted to a 190˚ engine block on a hot day could indeed engage it if there wasn't much/any cooling air blowing through the radiator. Say sitting idling at the light.

As others have noted, when the stock fan engages, you can indeed hear it.

papaindigo · **Posted:** Mon Aug 06, 2012 8:07 pm

naturist - I'll try to clarify a bit. The fan clutch (OEM or Hayden) engages based on a bimetal coil on the front of the clutch that is sensitive to air temp off the radiator which should be about 30F or so below engine temp or per the Hayden site "Engages at about 170° radiator air temperature (about 30° lower than coolant temperature)."

This means the Hayden clutch engages at an engine temp on the order of 200F or a bit higher which is at the very beginning of an overheat cycle. The OEM clutch engages somewhat higher IIRC something like 220F+.

Setting aside the discussion of weak or failed OEM fan clutches the fact that the Hayden engages early in a potential overheat cycle means it stops that cycle right at the start in contrast to a functional OEM fan clutch which cuts in later and has to play "catch up", so to speak, to stop over heating. In an engine overheat situation it's always better to stop temp rise early than it is to catch temp rise later and try to both stop the rise and reduce the temp.

warp2diesel · **Posted:** Mon Aug 06, 2012 9:59 pm

papaindigo wrote:

naturist - I'll try to clarify a bit. The fan clutch (OEM or Hayden) engages based on a bimetal coil on the front of the clutch that is sensitive to air temp off the radiator which should be about 30F or so below engine temp or per the Hayden site "Engages at about 170° radiator air temperature (about 30° lower than coolant temperature)."

This means the Hayden clutch engages at an engine temp on the order of 200F or a bit higher which is at the very beginning of an overheat cycle. The OEM clutch engages somewhat higher IIRC something like 220F+.

Setting aside the discussion of weak or failed OEM fan clutches the fact that the Hayden engages early in a potential overheat cycle means it stops that cycle right at the start in contrast to a functional OEM fan clutch which cuts in later and has to play "catch up", so to speak, to stop over heating. In an engine overheat situation it's always better to stop temp rise early than it is to catch temp rise later and try to both stop the rise and reduce the temp.

Yup, lots better than blowing a head gasket or cracking a head.

A Parent Bore Cast Iron Head/Block Diesel engine can be designed to operate at 275F by switching to propylene glycol with all of the water boiled out of it. The engine efficiency does go up. If you want to try the trick, find an old Mercedes 300D and go for it, they have worked out. Our CRDs have wet sleeves and aluminum heads, therefore doing the 275F/propylene glycol gig with the CRD is playing Russian Roulette with a fully loaded revolver.
Since I do not Gamble, especially with loaded firearms or my engine, the Severe Duty Hayden Fan Clutch and Mopar 11 blade nylon fan is the safest bet. Besides there is nothing more satisfying than having you wife not complain about the AC being wimpy when it is hot out.

joelukex4 · **Joined:** Thu Sep 29, 2011 4:54 pm **Posts:** 386

New to this subject but I have had no issue with my '05 whether towing or not.

Question I have is why no one talks about the auxiliary fan and what its function is?

papaindigo · **Posted:** Wed Aug 08, 2012 8:21 am

There really is no auxillary fan. Many/most vehicles nowdays have 2 fans the serve 2 different primary purposes:
1. main engine cooling fan located between the front of the engine and the back of the radiator or, to put it another way, behind all that "stuff" behind the grill. That fan, which back in the olden days used to be a fixed fan that ran all the time at a speed directly related to engine rpm, is generally either clutched (like that on the CRD) with the clutch set to engage based on radiator temp or electric with a termostat triggered by coolant temp somewhere in the system. The only "benefit" to the latter 2 fan setups is 1) they only make noise when engaged/running and 2) they make the mpg folks happy as by not running they boost mpg a bit and don't use a few hp. FYI IMHO the clutch fan is the better of the two as it runs more or less at idle all the time due to clutch friction hence it provides a bit of air flow over the radiator at all times.
2. AC fan that is typically 2 speed and located just behind the grill in front of all that "stuff". The primary purpose of this fan is to move air across the AC condensor when engine/vehicle speed are not enough for the condensor to function properly. To put it another way this fan's purpose is to boost AC performance under certain operating conditions.

Obviously any fan the moves air past the condensor and radiator "helps" both systems. In the real world the main engine cooling fan and vehicle speed do most of the work so that with Kap's fixed fan or even the Hayden and 11 blade nylon fan more air is moving thru that "stuff" hence there is less need for the AC fan and the AC works better due to more and cooler air flow. I won't say the AC fan does nothing for engine cooling as it obviously does something but it's only incidental and not much.

The above is somewhat simplistic as things are complicated by heat in one system impacting cooling ability in another system in all that "stuff" and the fact that the tranny cooler is built into one of those systems (in the CRD it's in the bottom of the AC condensor IIRC while in other vehicles it's in the bottom of the radiator). I'm not particularly fond of cooling radiators being "stacked" in the same air flow and don't know why that's done as opposed to side by side thicker units. Of course with the CRD what's stacked is AC condensor, radiator, and intercooler.

Hayden clutch function question

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