Cooling fan clutch mods to engage earlier?
 

I have been searching, but I cannot seem to find a thread somone had about modding the thermal fan clutch to make it come on earlier. Mine gets pretty hot before it engages. Fan and clutch are both new. It does not overheat mind you, but the gauge climbs fairly high when idling in 100* heat. "MA" area for you gauge letter readers. :) Normally runs at the "O-R" on freeway. I am a little worried about what will happen when I repair the AC and start sitting at those long lights. Thanks.

dont have a clue get rid of the clutch fan and get a flex fan and maybe a 4-core radiator

I also have a new thermal clutch fan. When idling it does not come on until 205-210F. When driving it usually comes on at 200F.(engine coolant temps)

The fan clutch is controlled by the bimetallic spring visible on the front. When it gets hot enough it "locks" then fan pulling air through the radiator. When it cools it "unlocks" and pulls little air. It also makes less noise and less drag giving better gas milage.

So you can:
1) replace the bimetallic spring with one that expands at a lower heat range. You'd probably have to hit the junk yard and test a few dozen springs to see if any do. Good luck. If you find the right spring let me know.
2) Get a non-thermal fan clutch. It will be noisy and perhaps lower your gas mileage slightly. It should be less noisy and have less drag than a solid(non-clutch) fan.

Please note that the stock fan moves much more air than any eletric fan I've seen. I would not change to electric.

I notice that the spring rests on a little pin. I wonder if you can alter the temp setting by putting a small shim on the pin, thereby changing the start point of the spring?? Or maybe I just need to stretch the spring a little. I know there was a thread here someplace that talked about this alteration.

When you hook up the a/c, the extra heat generated by the condensor will make the clutch engage sooner. I wouldn't worry about it too much. It's doing what it was designed to do.

I altered my fan clutch to come on earlier. You may have seen the post on a recent thread someone had about retrofitting a clutch fan on a truck that had a fixed fan.

If you have a standard fan clutch(non heavy duty), then the outside of the spring is held in place by a piece of sheet metal with a little slot in it. I simply used a dremel and cut a new slot. I cut the new slot so that there is only about 1/32" between the slots. This seems thin, but it is enough metal to hold the spring as there doesn't seem to be much force on the spring itself. This new slot it cut towards the direction of the spiral(towards the center).

Just with that much of a change, the fan now comes on after I get off the freeway after a fast run, even with without the AC on. With the AC on(I only use it when it is pretty hot out), it engages much of the time around town, but will disengage on the freeway.

Before the change, it would get almost to the top of the normal range, a little too hot for me. It runs around R most of the time but will get on the M if it is hot out. What's nice is that if you don't like the change, you simply put the spring back in the original slot.

Good Luck.

Thanks everyone! Gotta go with my motto, "If it aint broke fix it till it is"! I hate seeing it get toward the top before the fan cools her off. '79 Indy, you basically uncoiled the spring by 1/32, correct? Thanks again.

Oh man you guys are my kinda people! :)

79Indy, got a Hayden fan clutch that I "dremeled" just like you described.

And TJ460 I'm with you, if you wait til it's broke, that's called "poor maintenance" or something like that. :)

We are having the same symtoms, it ain't over heating just the gauge is climbing higher than it used to is all. Can't use the A/C in town, not that I usually do anyway, but want it to work right, might be a symtom of something wrong?

Last year changed from a 3 core to 4 core radiator.

Just got done changing out the water pump, the old one was weeping out the back, and bought a new "Flow Kooler" (dumb name huh?) that's got 12 fins on the impellor and their backing plate they advertize too. It definately does something better, but not sure yet if it can do what "we" want.

Summit sells two models of Flow Kooler and after looking at the flow Kooler website realized the slightly more expensive one with a "letter suffix" is the one with the 12 fin impellor the other is a plain 6 fin with their piece of galvanized sheet metal. Make your own if that's all you want IMO.

Alvin in AZ (first post here:)

I am running the Edelbrock water pump on a 400. I don't know if they are something special because I got it in a trade for some other stuff. It is just what I happened to have when my old pump started looking shakey. Seems to work fine though.