Fan Clutch

John,
I agree with your assessment of the lug nut situation. I too am running my old,
stock lug nuts with Alcoas. I was only using this example as an analogy, not to be
taken literally. My point is that the 5/16" studs on the water pump flange are too
short for the Hayden 2797 fan clutch. I might get by with using some red locktight but
there is no space for the lock washers that Hayden even supplies with the clutch. The
issue was that the fan could come off, not the Alcoas. I probably used a poor analogy
but I am wondering if anyone else has run into this with the Hayden 2797 clutch.

Phil Swanson

> Phil,
> It is NOT necessary to install the longer studs to use the Alcoa Wheels
> on the GMC. The original lug bolt length provides sufficient threads
> for 100 % strength when using Alcoa wheels. The pitch diameter for a
> 9/16 NF thread is 0.526". The GMC studs, Alcoa wheel and nut
> combination allows for 0.532" of thread, which is more that the pitch
> diameter of the stud. The longer stud does not provide more strength,
> it just has more threads exposed. The only reason that I would replace
> studs would be if they had been streached. You can check that by
> running a lug nut the entire length of the stud and you should be able
> to do it with your fingers without any resistance. Just be sure that the
> threads are clean.
>
> J.R.Wright
> 77 Eleganza II
>

> >
> > Scott, Not true, unless your set up is different than mine. I assembled my
> > fan to the 2797 outside the GMC shroud (on the workbench) and then removed the
> > four bolts mounting the rubber shroud, removed the band and spring and then
> > removed the lower r/h engine to shroud mounting bracket for clearance and the
> > assembly slid right in place (with some manipulating). However, I am having
> > trouble with the four mounting studs in the water pump flange being long enough
> > because the 2797 is much thicker than the stock clutch at the mounting flange
> > where it bolts to the water pump. Kind of like Alcoa wheels using stock studs
> > where no threads are showing past the nut. Don't want the fan flying off at high
> > speed so I am going to take the clutch back out and switch to longer bolts with
> > lock washers. The Hayden is not quite a "bolt up" in my GMC.
> > Haven't run it yet to see if I have the constant roar problem yet. Maybe we
> > got some bum dope on this being the best clutch, time will tell for me.
> >
> > Phil Swanson
> > 73 Canyonlands 23'
> >

> >
> > > (By the way, to install the
> > > 2797, you must assemble it to the fan inside of the fan shroud before you
> > > mount it to the water pump)
> > >
> > > > -----Original Message-----
> > > > From: owner-gmcmotorhome
> > > > [mailto:owner-gmcmotorhome]On Behalf Of Billy Massey
> > > > Sent: Thursday, April 15, 1999 6:16 PM
> > > > To: gmcmotorhome
> > > > Subject: GMC: Fan Clutch
> > > >
> > > >
> > > > I went be boppin' into the local auto parts store that handles Heydon
> > > > clutches and said I wanted a 2797. A girl said sure thing. She came back
> > > > with a nice looking blue box and I asked her how much she wanted for it.
> > > > She looked at a book and said $128.95. uhhhh, ain't that a bit much for a
> > > > dern fan clutch? I admit, it's been quite a while since I've bought one,
> > > > but that seems about twice too high.
> > > >
> > > > I called Gateway a minute ago and they want $98 for theirs. I forgot to
> > > > ask what brand they was peddeling.
> > > >
> > > > Am I livin in the past or what?
> > > >
> > > > bdub
> > > > '76 Palm Beach
> > > > In The Heart o Texas
> > > > www.web-access.net/~bmassey/
> > > > icq # 202333
> > > >
 
Easiest way to check for an operative fan is to use the procedure in the
repair manual. cover the front of the radiator, insert a thermometer
through one of the holes in the fan guard making sure it does not touch the
fan. Start the A/C and run the engine until the temp on the thermometer
gets to 150-190 degrees F. The fan should engage between these temps. If
it does not it is bad. Don't run the temp about 190 degrees. After the roar
starts, remove the radiator restriction and within a few minutes the temp
should return to normal and the roar should stop.

When the engine is cold you should not be able to spin the fan around more
than 5 times. there should be a slight drag on the fan as you spin it with
your finger.

>There's sure been a lot of info posted on this subject. Thanks Jim B.,
>Duane S., and Clarke S.
>
>I maintain a detailed listing of preferred parts for our particular coach
>to reduce the possibility of getting the wrong parts installed after a
>failure on the road, and have some question marks for "fan clutch".
>
>OK. Let's see if I have this straight..........
>
>Since I don't hear a roar when starting cold, and have never heard it when
>pulling grades (10,000') at full temperature, my fan clutch is not working
>and should be replaced (even if I've never overheated).
>
>On my '76 455, the Hayden part # for an OEM replacement clutch is 2705, and
>the # for a heavy duty one is 2747 (but it might "roar" more). Considering
>my lack of experience at over heating, I'm not even considering the 2797.
>
>Since I don't run hot, I'm inclined to have the 2705 installed (don't
>particularly want to hear any unnecessary noise). All this, of course,
>assumes I have a pump with a 5/8" shaft. Are the numbers different for
>pumps with 3/4" shafts?
>
>Sorry to stretch this thread so far (g), but want to get it right.
>
>TIA,
>
> ___________
>Dave (& Dege), '76 Royale /_][__] [_] | "SR JAMES"
> Santa Barbara, CA *-O------OO--*
>
>
>
>
Tom & Marg Warner
Vernon Center NY
1976 palmbeach
 
OK. I got it!

As long as I can still go up I15 to Las Vegas (100+) and over I70's
Loveland pass (10K'+) to Denver without overheating, that is, under 3/4 on
the gage using an upgraded NAPA temp. sender, I'm going to leave it alone.

But when and if I have an overheating problem, I'll suspect the fan clutch
and have a Hayden 2705 or NAPA 771303 installed. And if that don't work,
I'll risk the "roar" and have the Hayden 2747 installed.

Meanwhile, I'll have it flushed, pressure tested & recharged with 50/50 mix
every 24 months or 25K, which ever comes first.

Thanks Gary. (Did they get that wreck pulled of your beautiful beach yet?)

Paranoia again at bay,

___________
Dave (& Dege), '76 Royale /_][__] [_] | "SR JAMES"
Santa Barbara, CA *-O------OO--*
 
Thanks Mark, Tom, Rick & Duane.

I do have the NAPA 6469 temp sender, so I'm pretty sure It's staying cool.
But I guess instead of waiting to need it, it'd be smarter to deal with it
now. The next time I have any mechanical work done, I'll have it tested per
the procedure Tom outlined (Oops. I should have read the book before I
asked.), and replaced if it's no good.

I was prepared to have either a Hayden 2705, NAPA 771303 or Delco 14-4208
(which sound like they may be identical) installed, or if really brave, the
Hayden 2747. But then, remembering that I should check the books before
hand, I dug out the GMCMI Parts Interchange Index to confirm part numbers.
Guess what? More confusion. It lists the following;

Engine, Fan Clutch, 455 Engine
GMC 22050648 [this probably means GM, not GMC]
Ford E1TZHA616A [Ford ?]
Imperial 1215049
Murray 271303
NAPA 271303
NAPA 271301

Engine, Fan Clutch, 455 Engine - No Roar [separate category ?]
Hayden 15-4298
GM 1259772

Note that none of the numbers I am considering are listed, including the
heavier duty Hayden 2797 that Duane recommended. Is this one of those
times when there's more than one right answer? Are all these "acceptable"
choices, but not necesssarily ideal? It's really hard to believe there is
so much cunfusing information out there.

Now here's a really worth while challenge for this amazing GMCnet; Using
the GMCMI Parts Interchange Index as the start, and the awsome experience
of you netters, develope an updated "consensus" listing, and publish it
here as well as submit it to GMCMI for revision of their book. At the very
least, we should be able to searate the "preferred" from the "will work in
an emergency".

Can we keep this thread going long enough to provide a reasonable amount of
confidence for those concerned with this function or our GMC's?

TIA

___________
Dave (& Dege), '76 Royale /_][__] [_] | "SR JAMES"
Santa Barbara, CA *-O------OO--*
 
>... 2797 NEVER stopped "roaring", and the 2747
>"roared" continuously until I reached 45 MPH....
>All I want is the same fan clutch as my original.
>It hardly ever came on.

Its reasonably easy to adjust the thermostat on the fan clutch. To adjust
mine I use a dremmel tool cut-off wheel to make additional slots in the
bracket that holds the fixed end of the thermostat. You can then move the
fixed end of the thermostat from slot to slot until you get the best
tradeoff between noise and cooling response. It can even be adjusted after
the clutch is installed. I used a paper clip to reach in and grab the fixed
end of the thermostat and move it from slot to slot.

Caveats:

1) This does void the warranty on the fan clutch so be sure your clutch
actually works before modifying it.

2) Be sure that you know how well your temp gauge is working. The original
temp gauges where calibrated to show a half scale reading when the engine
is overheating (makes no sense to me!). The NAPA TS-6469 temp sender will
fix this (per previous posts).

When the fan clutch is working correctly the fan should make noise on hot
days or under heavy loads. Yes, it is annoying but thats what keeps the
engine cool...

My experience it that the thermostats on these fan clutches are not all
that great. If you adjust it to work well on hot days its tends to be too
aggressive on cooler days. If you adjust it so its quiet on cool days then
it tends to lag on hotter days.

Dave
73 Sequoia
 
Dave
>From what I can gather, you're the only guy who has been able to
keep track of, and sort out, the Fan clutch dialogue. I see you did a
great job on the 455; did you keep notes for the 403 (mine), and do
you have The Definitive Summary !!

Thanks
Mike Beaton........confused in NS
 
Dave, thanks for the idea about moving the anchor point of the thermostatic
spring. You or someone else commented on this about a month or two ago, but
when I looked at the Hayden, there were either one or two sets of "ears" to
hold the spring at either 360* or 180* intervals. It wasn't obvious how I
could add other anchor points, because the one or two "ears" were the only
metal close enough to the center of the clutch to reach the end of the
spring. (That sounds like Greek to me and I just wrote it)

Anyway, I still have not given the Hayden #2705 a test-run, so I don't know
if I still have a problem or not. So much has been written about this, I
will report back.

Thanks for the help.

Scott Shean
78 Royale
Baton Rouge, LA

> -----Original Message-----
> From: owner-gmcmotorhome
> [mailto:owner-gmcmotorhome]On Behalf Of Dave
> Sent: Monday, April 19, 1999 8:24 AM
> To: gmcmotorhome
> Subject: Re: GMC: Fan Clutch
>
>

> >... 2797 NEVER stopped "roaring", and the 2747
> >"roared" continuously until I reached 45 MPH....
> >All I want is the same fan clutch as my original.
> >It hardly ever came on.
>
> Its reasonably easy to adjust the thermostat on the fan clutch. To adjust
> mine I use a dremmel tool cut-off wheel to make additional slots in the
> bracket that holds the fixed end of the thermostat. You can then move the
> fixed end of the thermostat from slot to slot until you get the best
> tradeoff between noise and cooling response. It can even be adjusted after
> the clutch is installed. I used a paper clip to reach in and grab
> the fixed
> end of the thermostat and move it from slot to slot.
>
> Caveats:
>
> 1) This does void the warranty on the fan clutch so be sure your clutch
> actually works before modifying it.
>
> 2) Be sure that you know how well your temp gauge is working. The original
> temp gauges where calibrated to show a half scale reading when the engine
> is overheating (makes no sense to me!). The NAPA TS-6469 temp sender will
> fix this (per previous posts).
>
> When the fan clutch is working correctly the fan should make noise on hot
> days or under heavy loads. Yes, it is annoying but thats what keeps the
> engine cool...
>
> My experience it that the thermostats on these fan clutches are not all
> that great. If you adjust it to work well on hot days its tends to be too
> aggressive on cooler days. If you adjust it so its quiet on cool days then
> it tends to lag on hotter days.
>
> Dave
> 73 Sequoia
>
>
 
>Dave
>>From what I can gather, you're the only guy who has been able to
>keep track of, and sort out, the Fan clutch dialogue. I see you did a
>great job on the 455; did you keep notes for the 403 (mine), and do
>you have The Definitive Summary !!
>
>Thanks
>Mike Beaton........confused in NS

For sure no definitive summary.

But I gotta tell ya, I'm more than a little concerned that ther's so damned
many supposedly good part numbers. I sure hope I find out that most of then
are made by the same mfg., and fall into the "preferred" category, but
seriously doubt it.

So, assuming you don't have the GMCMI interchange index, it says that the
following clutches work for the 403 engine; Murray 271306, NAPA 271306, GM
22050648 & NAPA 271301. Interestingly, according to the index, the 1st 2
part numbers will also work on the 455, but the last 2 won't. Also, there
are no Hayden parts listed as usable for your 403, and while there several
numbers listed as "no roar" for the 455, there aren't any such listings for
the 403. I guess you're gonna be roarin', huh? (g)

Unfortunately, I only kept the opinions related to the 455, but others on
GMCnet will likely provide several more recomendations.

I think our only choice is to give weight to the suggestions based on the
perceived credibility of the contributor.

HTH

___________
Dave (& Dege), '76 Royale /_][__] [_] | "SR JAMES"
Santa Barbara, CA *-O------OO--*
 
Just couldn't resist (hope there isn't a related post later in the digest);

Now we have another part number to consider.

Joan Paullin has weighed in with yet another success story.

This time it's a Delco 15-4644.

Seems like dang near any clutch will do!

Maybe we'll only go down hill :-)

___________
Dave (& Dege), '76 Royale /_][__] [_] | "SR JAMES"
Santa Barbara, CA *-O------OO--*
 
>.... were either one or two sets of "ears" to
>hold the spring at either 360* or 180* intervals. It wasn't obvious how I
>could add other anchor points, because the one or two "ears" were the only
>metal close enough to the center of the clutch to reach the end of the
>spring.

I cut additional slots in the metal tab that already has the bimetallic
coil spring attached. This will give you a few degrees adjustment in either
direction. Do not adjust the coil 180 degrees by attaching it to the
opposite side. This will keep the clutch always engaged or never engaged
(depending on which way you turn the spring). The amount of adjustment
needed to change the temperature is very small. I cut four new slots in
mine, two on each side of the existing one.

I wanted to make my clutch a bit more aggressive. I do most of my traveling
in the hot summer months when the outside temps are 90+ degrees. So I chose
to put up with a little more fan noise in order to get cooler engine
operating temps. In the end I moved the spring one notch and that did the
trick. Unfortunately I cant remember if that was CW or CCW and the GMC is
not here so I cant look at it to tell you.

But, like I said before, there is a tradeoff between noise and cooling.
This adjustment is just right on hot days. Keeps the engine temps rock
solid up to nearly 100 degrees outside air temp. But on cooler days you
still hear the fan running to about 70 degrees outside air temp. Below 70
its mostly quiet. I don't think the fan is needed much below 80 or so
unless you are pulling a load or going up a grade. But since I do a lot of
hot weather driving I am willing to put up with the extra noise on cool
days to keep things nice and cool under the hood on hot days.

Dave
73 Sequoia
 
Just a thought, but IF you have installed both the auxiliary fan assisted
tranny cooler AND the fan assisted engine oil cooler and are dumping large
amounts of THAT heat by secondary means, shouldn't this make the concerns
about the fan clutch less relevant?
Dick 75 PB in Atlanta

> >.... were either one or two sets of "ears" to
> >hold the spring at either 360* or 180* intervals. It wasn't obvious how I
> >could add other anchor points, because the one or two "ears" were the only
> >metal close enough to the center of the clutch to reach the end of the
> >spring.
>
>I cut additional slots in the metal tab that already has the bimetallic
>coil spring attached. This will give you a few degrees adjustment in either
>direction. Do not adjust the coil 180 degrees by attaching it to the
>opposite side. This will keep the clutch always engaged or never engaged
>(depending on which way you turn the spring). The amount of adjustment
>needed to change the temperature is very small. I cut four new slots in
>mine, two on each side of the existing one.
>
>I wanted to make my clutch a bit more aggressive. I do most of my traveling
>in the hot summer months when the outside temps are 90+ degrees. So I chose
>to put up with a little more fan noise in order to get cooler engine
>operating temps. In the end I moved the spring one notch and that did the
>trick. Unfortunately I cant remember if that was CW or CCW and the GMC is
>not here so I cant look at it to tell you.
>
>But, like I said before, there is a tradeoff between noise and cooling.
>This adjustment is just right on hot days. Keeps the engine temps rock
>solid up to nearly 100 degrees outside air temp. But on cooler days you
>still hear the fan running to about 70 degrees outside air temp. Below 70
>its mostly quiet. I don't think the fan is needed much below 80 or so
>unless you are pulling a load or going up a grade. But since I do a lot of
>hot weather driving I am willing to put up with the extra noise on cool
>days to keep things nice and cool under the hood on hot days.
>
>Dave
>73 Sequoia
>
>
 
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