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Suburban Fan Clutch

ChevyMan on Mon June 15, 2009 9:14 PM User is offline

Year: 1985
Make: GMC
Model: Suburban
Engine Size: 350
Refrigerant Type: R134a
Country of Origin: United States

Hello, all. I wrote about this truck earlier. Anyway, I have a quick question. I read about a recomendation to lock up the fan clutch on a Toyota truck (I think that was the vehicle). Anyway, I determined that the aftermarket fan clutch on my sSuburban was not locking up as it should. I drilled a hole through it and installed a 1/4-20 bolt. This has the effect of locking the clutch solid. Do you think that there would be anything wrong with doing this? I thought about it throughing off the balance, but only the head of the bolt and the nut on the other side would have any effect, as the part of the bolt that is inside the clutch is filling the void created by drilling the hole. But, I had to remove to of the fins on the clutch to make the mod, so it kinda evens out. I am not worried about that. It is not hot enough today, only about 70 degrees, to really tell how it is going to work, but I know it is cooling better that it was.

Just to recap, here is what has been done to the truck:

1. Completely dissasemble the system
2. Flush everything but the compressor
3. Drain the old oil from the compressor (there was not to be found)
4. Add 8 oz new oil, half to the compressor half to the new accumulator
5. Install new accumulator
6. Install new blue orifice
7. Install new condenser (updated type, not true PF but has more and smaller diameter tubes and fins)
8. Recharged with 48 oz R134a.
9. Modded the fan clutch


I got 35 degrees from the dash vents today.

Anything else I should do?

fonebone on Tue June 16, 2009 2:03 AM User is offline

Hi ChevyMan; Any unbalance would be difficult to detect without a good balance rig. Sure, you're probably slightly out , and all that would really do is slightly(depending on how much out it is) hasten the water pump bearing wear. Remember, clutch fans are not rated much past 3500 rpm before they de- clutch. Now that you have the clutch locked, DO NOT over rev the engine or you will explode that fan!!! Think twice before you dump the pedal to the floor trying to pass someone. When the hot spell is over, take out that bolt and let it go back to stock. Hope this helps

ChevyMan on Tue June 16, 2009 9:51 AM User is offline

I hadn't thought about the fan not being rated for full engine RPM. I will have to get another clutch, as drilling the hole let out the "magic oil" that makes the thing work. Also, it was not working right anyway. I just remember that in years past, and not so past (late 80s S-10), there were direct drive fans. I also read about putting some lock washers in a Toyota fan clutch to make it solid. I guess those can be taken apart. Oh well. It really does seem to cool down faster, but I can't say for sure as it was too cold outside to compare. When it gets back up closer to 90 outside, I'll get more pressure readings.

Does anyone know who makes the best fan clutch? Maybe ditch the mechanical fan altogether and salvage a dual electric fan setup from a Lincoln? What would you guys do?

Cussboy on Tue June 16, 2009 2:41 PM User is offline

The board sponsor is likely to recommend a factory fan clutch. I have used Hayden fan clutches on my import truck, was lifetime guaranteed back in 1995 when I bought it. Mine came from Pep Boys.

fonebone on Wed June 17, 2009 1:44 AM User is offline

Hi ChevyMan; I have tried many, and have settled on Flex-A-Lite as THE best. Summit Racing has them. (Hope no one minds the plug)Good price, roars like a jet engine till cruise speed, and drops those vent temps as far down as they can go. Please try one, it is just the ticket if you want to stay with a factory style setup.

Edited: Wed June 17, 2009 at 12:34 PM by fonebone

ChevyMan on Wed June 17, 2009 11:45 PM User is offline

Thanks for the tip on the fan clutch. I will look into it. That locked up clutch really drags down the HP. I am really considering a Windstar, Tarus, or Mark VIII electric fan. According to other sites these are the most popular for swaps and probably the best electric fans you can get, either OEM or aftermarket.

fonebone on Thu June 18, 2009 1:10 AM User is offline

Remember, though, when you install large electric fans, you will draw a high, probably 20 +, amps to run them. That puts a real drag on the alternator and horsepower to run it. The clutch fan will run all the time, the electrics will be as needed. Consider both. The fans will only blow through the area they cover, the clutch fan will pull through every square inch of area on the condenser with shroud properly installed and sealed around the edges. Between the two, the clutch fan wins for max CFM, lower vent temps in the vehicle. Remember also, that electric fans blowing into the condenser do little to help lower temps in the radiator, which is working like mad to dissipate the heat from the engine and the extra heat coming at it from the hot condenser. Underhood temps spike on a really hot day, and a good roaring clutch fan helps a lot to cool things down in the engine compartment. Higher underhood temps lessen the life of hoses, plastic fittings, electrical components, etc. When it's BLAZING hot, I don't car how much horsepower it costs, I want to be COOL

Edited: Fri June 19, 2009 at 8:29 PM by fonebone

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