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4 bolt fan clutch solutions with a 195 degree t-stat

GM Guy

GM Guy

Manual Trans. 2WD Enthusiast
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Location
NW Kansas and SC Idaho
Hey all,

The long term game plan is to save up and install a year 2000 water pump and Leroy's new fan clutch system, but currently, I want to make the existing 4 bolt low flow 95 OEM system work for a bit longer, and with numerous trucks, it can be moved to another rig when I put the better setup on this one.

So, I ask you folks, for this sub part setup, what would be the best route? I am curious as to see if the Kennedy diesel special application fan clutch will ever kick out with the 195 degree t-stat. It is the AC Delco one that Leroy sells.

If it wont kick out, what clutch should I go with?

Any input appreciated, thanks!
 
The fan clutch doesn't read engien temp, it works off of the air temp going through the radiator. So once the stat closes, the radiator cools off, and it will kick off regardless. With that being said, I would just run a severe duty HAYDEN or something like that if it was mine.
 
Thought on GM OE grade from Rock auto? Surely as good as Hayden?

I am ordering for a 98 so I can mount the newer better fan options (9 blade steel or d-max fan) and I can have GM OE grade for 88 bucks, or Hayden for 112.
 
Dont worry Leroy, I am going big or not at all for the final version, year 2000 spin-on with Leroy's clutch on the long distance pullers.

But I need a short term solution ATM, and it will be swapped over to one of the lesser rigs (the bucket truck likely) once I upgrade.

Knowing what the test program is, I am confident any issue will be found if there ever was one. :) you gotta "leak" some photos, keep us all excited! :)
 
They are not on or off. The more heat on the metal wound spring the more fluid transfers locking up more, like a sliding scale, the have a max percentage of lock up- not 100%.
The severe duty has a steeper ramp up to lock up sooner, and gets a higher total lock up percentage.
Going from the stock Delco to the Hayden helped me fight the heat a little longer, and cool down a couple minutes earlier.
I REALLY want a on/off 100% lockup.

If you want a better fan than the 9 blade, the stock '95 hummer fan is (19.5") smaller and bolts up to the Hayden. Fanclutch for pickups.
Fan part number 4735-42599-103
 
OK, final dumb question. as long as its a Hayden with the same part number, there is no Severe Duty and non-Severe Duty, all of them should be Severe Duty, correct? Reason I ask is that one seller on ebay is 10 bucks cheaper than everyone else, but does not say anything about Severe Duty, but its a Hayden with the same number.
 
GM Guy said:
Hey all,

The long term game plan is to save up and install a year 2000 water pump and Leroy's new fan clutch system, but currently, I want to make the existing 4 bolt low flow 95 OEM system work for a bit longer, and with numerous trucks, it can be moved to another rig when I put the better setup on this one.

So, I ask you folks, for this sub part setup, what would be the best route? I am curious as to see if the Kennedy diesel special application fan clutch will ever kick out with the 195 degree t-stat. It is the AC Delco one that Leroy sells.

If it wont kick out, what clutch should I go with?

Any input appreciated, thanks!
Click to expand...

I do not know why this rumor exists. Perhaps someone somewhere had a problem where the bearings in the clutch locked up or something. I am here to tell you this is a rumor. The KD clutch kicks off.

Long time ago MGW suggested the reason GM raised the fan clutch turn on temp was noise complaints.

Regardless I run the Kennedy Diesel Low temp fan clutch and I have run it for 6 years. (ordered a new one last year as the 5 year lifetime was reached.)

Yes, the KD fan kicks off with a 195 degree T-Stat. I have run both temps in Patch. The 195 just gives me a higher ECT spike. I have run the 19" steel and the Duramax fan. In fact I am back to the 19" steel fan as a engine mount has sagged causing the Duramax fan to start rubbing the shroud. Since the Yank Converter install I find the 195 and KD clutch is a bad combo as I can spike over 210 going on ramp to freeway speeds. (Sustained high RPM plus converter heat add up quick.)

I have run the GM3 turbo along with both the HX40II and ATT. Make a difference in less cooling need with a bigger turbo, but, the KD worked very well with all 3.

Yes, The Hayden is ok. But it's just not as good as the KD clutch specific to the peak ECT spike before it turns on. Modding the damn spring is not easy and risks the clutch not shutting off. It's a narrow window controlling the valve via a spring. For $175 the Sale Price of the KD clutch - just spend the $75.00 extra and be done with it. Sure others have modded their clutch to temps unknown - I have failed on gas engine clutches and instead wound up raising the idle for AC in the ECM.

There are a few places I see a need for a better fan clutch system. Overcoming the delay of heating the thermal spring from the hot radiator and RPM dependent delay getting the clutch locked up is one area to reduce ECT spikes. Higher RPM the faster the clutch will lockup - so I have seen places with high throttle in lockup OD where the temp spikes with a trailer on a grade in over 100 degree weather. Dropping to 3rd would reduce the max temp of the spike.
 
Question:

On the stock 95 with 6 bolts holding the fan on, and a 97-early 99 clutch with 4 bolts holding the fan on, are the bolts the same, or do I need to get 4 97+ bolts?
 
Fan to clutch bolts are the same. You get 2 leftover bolts when you are done.
 
good deal.

@WarWagon, you are heck of a salesman, got the KD clutch in this past week. Got the new GM/ Delco 9 blade steel fan off ebay a few weeks ago. Way over budget, but oh well. :)

This will surely do me till Leroy's clutch is ready for market, then I will run one of those and move this setup to my 2wd 95. on this 95 K2500, it has the stock clutch with a poly fan on it, I assume the hummer fan? it will go on my good 93 spec clutch that currently resides in the 2wd 95, and that setup will then go into the 95 bucket truck.

Its a game of musical clutches on the 95 rigs... :)
 
Just a query about the spring mod.
Instead of bending the tip - could you not just unwind the spring to the point of changing the bend radius to set a higher temp engage and overwind it to re-set the radius of thd bend for a lower temp engagement? Im on my second brand new Hayden severe duty in my hummer and it still rdfuses to engage and cool down. If I run a strap around the clutch to bypass the coupling its noisy but cools like a superstar.
 
The spring is only adjusted by 1/8" maximum. Unwinding the coil is going to move far more than that. If the coil is not linear tension it will want to flex wherever you create a crease or bend and will not allow proper engage / disengagement.

If you install yet another new fanclutch, i would suggest running it stock and ensure operation before messing with it- something funky seems to be going on. Maybe do a kennedy so your not havng to mess with it?


Maybe a partial blockage in airflow through radiator not allowing the hot air to flow evenly on the face of the clutch?

Thats a wacky one having 2 bad in a row.

May I ask why not change over to the balanced flow waterpump instead of pouring more money into the system we know was designed wrong?
 
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