GARY PAGE
10-03-2003, 17:54
Fan Clutch Modification
I recently purchased a new hevey duty Heydon fan clutch for my 95 3500 6.5 in an effort to reduce operating temps. The truck has the 97 cooling mods with dual 180 therms; but ran the stock 6.5 fan and clutch. I always run 185 when empty; but under load on grades with my 5th wheel I was running up 230 and the fan would come on and take the temp down to 205 or so and the cut off and then it would go back up. It was like the fan was not coming on soon enough and was no better than my original clutch. I decided to work on the thing and figured out which way the spring moved under heat using my lighter and decided to modify the unit. First I operated on my old one. I noted the pocket where the tang of the spring helix fits into the clutch hub has about 0.125 inch of slop within the pocket which would allow me to change the engage point of the clutch. In stock position the tang is centered in the pocket. The spring is glued in the pocket with silicone, which offers some thermal resistance to the hub as well. In short I removed the silicone and moved the spring tang in the hub socket counter clockwise 0.125 inch from stock position, it took some grinding with a die grinder on the hib pocket. I then re-attached the tang using JB weld. The JB weld has a lower thermal resistance than the silicone so the spring will conduct heat from the hub, thus react quicker. Both of these modifications produced the desired affect and my max temp last week end was 210 on a 3 mile 6% grade pulling 8500 LB and most of the time it was 190 or less. It runs much cooler and I can here the fan coming in earlier. It took me about 1 hour to make the modification and it works great so far. It probably not as good as the Kennedy clutch hub; but I assure it going in the right direction and much better than the stock set-up for and hour of my time and a tube of JB weld! Me so happy!!!
I recently purchased a new hevey duty Heydon fan clutch for my 95 3500 6.5 in an effort to reduce operating temps. The truck has the 97 cooling mods with dual 180 therms; but ran the stock 6.5 fan and clutch. I always run 185 when empty; but under load on grades with my 5th wheel I was running up 230 and the fan would come on and take the temp down to 205 or so and the cut off and then it would go back up. It was like the fan was not coming on soon enough and was no better than my original clutch. I decided to work on the thing and figured out which way the spring moved under heat using my lighter and decided to modify the unit. First I operated on my old one. I noted the pocket where the tang of the spring helix fits into the clutch hub has about 0.125 inch of slop within the pocket which would allow me to change the engage point of the clutch. In stock position the tang is centered in the pocket. The spring is glued in the pocket with silicone, which offers some thermal resistance to the hub as well. In short I removed the silicone and moved the spring tang in the hub socket counter clockwise 0.125 inch from stock position, it took some grinding with a die grinder on the hib pocket. I then re-attached the tang using JB weld. The JB weld has a lower thermal resistance than the silicone so the spring will conduct heat from the hub, thus react quicker. Both of these modifications produced the desired affect and my max temp last week end was 210 on a 3 mile 6% grade pulling 8500 LB and most of the time it was 190 or less. It runs much cooler and I can here the fan coming in earlier. It took me about 1 hour to make the modification and it works great so far. It probably not as good as the Kennedy clutch hub; but I assure it going in the right direction and much better than the stock set-up for and hour of my time and a tube of JB weld! Me so happy!!!