| Fan clutch brands to buy and avoid [message #130614] |
Fri, 17 June 2011 16:13  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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I have a GMC (Isuzu) W4 gas tilt cab truck at work with a rebuilt 2 year old SB Chevy TBI and a 2 year old radiator that runs hot above 55 MPH. You get normal fan roar at startup cold, so there is silicone juice in there, but the fan never seems to engage when needed. I think the bimetalic spring or valve is not working. I know these things are reboxed, but is there a certain store brand we should avoid or look for as found in the GMC Motorhome community. The discussions have been so long and heated that I can't face searching them all. (lazy me) Short answers are fine.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Fan clutch brands to buy and avoid [message #130616 is a reply to message #130614] |
Fri, 17 June 2011 16:43  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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John,
If the engine is running hot at 55 mph, your problem is not the fan clutch. The fan clutch is there to handle exceptions and not normal cooling. Exceptions would be things like idling in traffic with the AC on or hauling a lot of weight up a long grade. The clutched fan assists the cooling system exceed it designed heat exchange rate for short periods of time.
I'd be looking at things like incorrect radiator, obstructed radiator (both inside and outside), thermostat not opening fully, and ignition timing.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Fan clutch brands to buy and avoid [message #130619 is a reply to message #130614] |
Fri, 17 June 2011 17:06 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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| JohnL455 wrote on Fri, 17 June 2011 17:13 |
I have a GMC (Isuzu) W4 gas tilt cab truck at work with a rebuilt 2 year old SB Chevy TBI and a 2 year old radiator that runs hot above 55 MPH. You get normal fan roar at startup cold, so there is silicone juice in there, but the fan never seems to engage when needed. I think the bimetalic spring or valve is not working. I know these things are reboxed, but is there a certain store brand we should avoid or look for as found in the GMC Motorhome community. The discussions have been so long and heated that I can't face searching them all. (lazy me) Short answers are fine.
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Sir: I have found clutch fans that would roar at start up but would not engage at high temps. Is there any sign of dirty leakage at the bearing? I`m not trying to start a fan war, but I have had good success with the Auto Zone fans. They usually show 3, standard, heavy duty and severe duty. I use the heavy duty on the GMC and I pull a trailer. This is what works for me.
C. Boyd
76 Crestmont
East Tennessee
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| Re: Fan clutch brands to buy and avoid [message #130623 is a reply to message #130614] |
Fri, 17 June 2011 17:12 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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It used to cycle at road speed on a warm day but no more, that's why I'm suspecting the clutch. I do know what you are saying that at road speed that the clutch is not needed. However in trucks where the road load is high they will cycle on and off I have found. The radiator is still shiny black and tubes still clean. (the only shiny thing on the truck) The rubber service caps on the unused ports were leaking so we had a 'poor man's coolant exchange' in the last month till I found the leaks. It's at 50% mix and the shrouds and obstructions check all look good. Initial Timing could be retarded, but the computer takes it from there, though it doesn't drive or sound like the timing is late. Up to 55 it sits on the stat and then above that climbs and the clutch never engages.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Fan clutch brands to buy and avoid [message #130625 is a reply to message #130614] |
Fri, 17 June 2011 17:16 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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No leaks and loud roar on start up. So I think the thermal switch is gummed up. I sprayed some WD-40 on the bimetalic for laughs. I'll go Auto Zone if we replace it. Thanks much.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Fan clutch brands to buy and avoid [message #130628 is a reply to message #130619] |
Fri, 17 June 2011 17:30 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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John,
Take a mirror and flashlight and look at the coil for dirt covering the coil.
That silicon oil attracts lot of dirt and will insulate it.
Tale brake cleaner and spray off the dirt.
On Fri, Jun 17, 2011 at 3:06 PM, Charles Boyd <covered-wagon@comcast.net> wrote:
>
>
> JohnL455 wrote on Fri, 17 June 2011 17:13
>> I have a GMC (Isuzu) W4 gas tilt cab truck at work with a rebuilt 2 year old SB Chevy TBI and a 2 year old radiator that runs hot above 55 MPH. You get normal fan roar at startup cold, so there is silicone juice in there, but the fan never seems to engage when needed. I think the bimetalic spring or valve is not working. I know these things are reboxed, but is there a certain store brand we should avoid or look for as found in the GMC Motorhome community. The discussions have been so long and heated that I can't face searching them all. (lazy me) Short answers are fine.
>
>
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> Sir: I have found clutch fans that would roar at start up but would not engage at high temps. Is there any sign of dirty leakage at the bearing? I`m not trying to start a fan war, but I have had good success with the Auto Zone fans. They usually show 3, standard, heavy duty and severe duty. I use the heavy duty on the GMC and I pull a trailer. This is what works for me.
> --
> C. Boyd
> 76 Crestmont by Midas
> East Tennessee
> _______________________________________________
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Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
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Jim Kanomata
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| Re: Fan clutch brands to buy and avoid [message #131389 is a reply to message #130614] |
Tue, 21 June 2011 21:59 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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I took Jim K's advice and today made an Rube Goldberg tool to clean the bimetalic spring without removing the shroud and clutch. Took a can of Zep Aerosolve spray degreaser and put a nozzel on it that would take the straw. Then I extended the straw with some 1/8" heat shrink for about 18" (unshrunk). With a helper to operate the can I could reach in between the blades and blast the spring which was gummed up with 18 years of road gunk clean. The inspection mirror showed a clean spring area. I haven't tested it yet but we shall see if it works now. 'Fix it in a can' is my favorite fix.... if it works. I'll report back. If you think about it if there is juat a slight weeping of fluid there, the shear volume of air going past there is huge over the years the road grunge can really build up and attract to the spring.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Fan clutch brands to buy and avoid [message #131894 is a reply to message #130614] |
Fri, 24 June 2011 20:10 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Well.... reporting back on the GMC W4 350 TBI truck, the "fix the fan clutch by cleaning the bimetalic spring" seems to have worked. I didn't drive it but our semi driver had to take the little GMC to Michigan to pickup what would not fit in the semi after a big Ford show we did there. I explained to him what I had done with spraying Zep Aerosolve on the thermal spring to wash off all the years of gunk on there. This truck was loaded way too heavy and he said the temp gauge ('on the stat' is at 1/2 on this truck) would start going up over half and then he would hear the fan kick in and it would come back down to half. He said he tryed to make it overheat and no luck. So I am proclaiming it fixed! Thanks to Jim K for the proding to try cleaning the spring before replacing the clutch. I thought that might work but his reinforcement cemented the theory. Worth a try if yours 1)still has it's silicone fluid, 2)works as it should at cold start up and then unlocks as it should, but 3)then never comes on when overheating, then this might fix it. John.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Fan clutch brands to buy and avoid [message #131896 is a reply to message #130623] |
Fri, 24 June 2011 20:40 |
rvanwin
Messages: 325
Registered: April 2007
Location: Battlefield, MO
Karma: 6
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Senior Member |
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| JohnL455 wrote on Fri, 17 June 2011 17:12 |
Initial Timing could be retarded, but the computer takes it from there, though it doesn't drive or sound like the timing is late. Up to 55 it sits on the stat and then above that climbs and the clutch never engages.
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Sounds like you have your problem solved so you probably are not running with Spark Advance (SA) retarded. However, I wanted to explain the timing with a computer controlled distributor. However, You indicated that initial timing might be retarded but that the computer takes over. It is true that the computer takes over but if the initial timing is retarded from what is set in the Initial SA Parameter in the ECM, then the engine will run that amount of retard across all rpm and MAP ranges. Initial timing needs to be set correctly so that what the computer commands for SA is accurate.
Randy & Margie
'77 Eleganza II '403'
Battlefield, MO
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