| Re: [GMCnet] Fan clutch follies [message #272345 is a reply to message #272294] |
Thu, 19 February 2015 17:58   |
powwerjon
Messages: 849
Registered: March 2013
Karma:
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Senior Member |
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Armand,
I have read your paper on the cooling issues you experienced and your observations were similar to conclusions that GMC discovered on their commercial motorhome chassis in the 70,s that air flow control is the Key to the problems of cooling. GM added the air control baffles to the GMC commercial motorhome chassis and commercial ”P” model chassis and on the GMC classic motorhome when they went to the 403 engine at TZE167V101285 for the motorhome, TZE337V101287 for the 23’ TransMode and TZE367V101312. Our first GMC the 77 Eleganza II 403 had the air control panels factory installed and it was about 40 coaches past the changeover. Our fan clutch was never that obnoxious in noise except when it failed and I did use the Hayden 2797 clutch as a replacement at that time. Fan Clutches have been a reoccurring theme since almost the beginning. They would come on and people reported that it sounded like the transmission downshifted. With many many articles in GMC motorhome marketplace and in the GMCMI Newsletter. I did add a front air dam spoiler of my design back in 2001 to direct more air into the radiator air path and to use the negative pressure after the spoiler under the coach to help extract hot air our of the engine compartment. It is the same one that is now sold by Jim K and works as advertised. As has been found by you and others the current selection of available fan clutches is not as good and/or reliable as they were 10 or more years ago.
http://www.gmcmhphotos.com/photos/general-pictures/p57278-engine-cooling-gm.html
Now to the present configuration on our stretch coach. Coach weight loaded aprox. 14700 lbs and pulling a 3800 lbs towed. For the last 2300 miles I have been running the John B. 10 blade nylon fan using the same 9222747 that you are using and the same unit that was used when running the 7 blade. When it is engaged It is difficult to hear the fan run as it is much quieter than the 7 blade metal fan, but you can hear it cycle as for it engaging over 45 I don’t hear it. IMHO I think the balanced even number of nylon fan blades will reduce the failure rate of the fan clutches along with less load on the impeller shaft of the pump. I have one of the AC Delco Heavy Duty Fan Clutch, like Jim K. sells, that I got from Rock Auto a few years ago that I want to test with this new fan when I get home. That way I will have almost 5K miles on the 10 blade fan and will be able to compare the 2.
Temperature gauge observations:
In the our first coach the 1977 the other items in the cooling loop were a 180 Robert Shaw 180 deg thermostat, the radiator has been recored with the HD core and I was using the newer temp sender that made the temp gauge mean something. The coolant would come up to temp, (180) and sit there all day long. If we were in hills or mountains then it would elevate just a little bit and you could hear the fan clutch engage slightly, and then shut off again.
The stretch has a very large air scoop under the bumper to direct air into the radiator but does not yet have the side and divider panels. I plan on adding the air direction baffles similar to Ken H. addition in the spring when I get home. It runs 190 deg thermostat and the temp stays locked at 190 except when when we are climbing in the mountains out west where it might move up a few degrees. I have a Mac Dash with all the gauges ( analog ) and the good sender here also.
This has always been a topic of great discussion for many years with many possible and different solutions.
J.R. Wright
30' Buskirk Stretch
Michigan
On Location in Tucson
> On Feb 19, 2015, at 6:19 AM, Armand Minnie wrote:
>
> JR, do you mean that you have not experienced the fan turning on at highway speeds? I have heard from many people about the same problem and still
> have the same opinion: the fan should not be turning on at 60 mph. If it does there is some issue that needs to be fixed. I am using an Autozone
> Torqflo 922747 which I think is a medium-duty clutch on the standard fan. I can tell when the clutch is engaged but it does not make much noise and it
> does not engage so that I can hear it once I get over about 45 mph.
> --
> Armand Minnie
> Marana, AZ
> '76 Eleganza II TZE166V103202
> http://www.minniebiz.com
> http://www.gmcws.org
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