Matt Mc_Carthy wrote in a message to Roy J. Tellason:

 MMC>> Well, you did say earlier that it runs hot without the shroud!

 RJT> Yeah.  Temp gauge runs up to between 1/3 and halfway when it's 
 RJT> been sitting there idling long enough.  Take it on the highway 
 RJT> and it gets way over there...

 MMC> That sounds backwards.  Are you sure you have a clean radiator and
 MMC> block core? ..............

Well,  when I was putting things together one of the things I did was to
take the two radiators to a local shop and ask for the best they could do
with them.  Unfortunately they couldn't do anything with the bigger one of
the two, so I ended up putting the smaller one in the truck.  The guy at
the local junkyward looked at that and told me I had about the smallest
radiator I could _have_ in a truck.  And as far as the rest of it goes, 
all hoses are new,  and my brother and I spent some time one day and
flushed the whole system out, completely,  did a real thorough job of it. 
I didn't have that stuff in there any 10 minutes like the label
recommended,  either,  I put it in and then drove over to his place,  about
an hour away.  Thermostat's new,  been replaced too in case the one I put
in there to begin with was bad.

This thing's geared real low at the rear (4.10?) and is also hauling around
a *lot* more metal than any lightweight,  it's a 3/4 ton truck.  And that's
not an overdrive transmission either,  so at highway speeds that motor is
working pretty hard.

 MMC>> cars were overheating.  This happened to coincide with the 
 MMC>> beginning of EPA requirements, and manufacturers "detuned" 
 MMC>> engines as a first step, which also resulted in higher engine 
 MMC>> temperatures.

 RJT> Which aspects of things had they changed there?  This motor came 
 RJT> out of a car which was a 1975 model year.  The truck is a 1978.

 MMC> Idle timing was set much "late" compared to earlier years of the 
 MMC> identical engine.  This increases engine heat considerably, and
 MMC> actually 'wastes' the heat being generated to produce the 
 MMC> horsepower.

I'm thinking that the timing on this might be a little far advanced,  that
maybe I oughta back it off some.

 MMC> Is that engine an inline 6?  What brand?

It's a V-8,  a 318 (mopar,  I don't drive much else).

 MMC>> Along with the higher temperatures, they began putting sealing 
 MMC>> strips at the rear of the hood, so the heat could no longer 
 MMC>> escape over the winshield as it did in older cars.

 RJT> I don't quite understand that,  there's a set of what looks like 
 RJT> vents across the bottom of the windshield,  but they sure don't 
 RJT> open into the engine compartment.  Dunno why they'd build things 
 RJT> that way.

 MMC> Those vents below the winshield are now the air intake vents for
 MMC> the passenger compartment.
 MMC> ............................

I don't remember offhand if there are any sealing strips,  though.  I *do*
remember those in my other truck (a Ford) and that they were falling off...

 RJT> This one's two parts,  if I remember right,  rivets in the center.

 MMC> See comments below!

 MMC>> At the same time, they changed to a smaller sized fan/water pump 
 MMC>> pulley (or a larger size crankshaft pulley), to speed up the fan.

 RJT> Now there's something I could probably fiddle with.  The whole 
 RJT> setup in this vehicle is a bit off,  there being this unused a/c 
 RJT> compressor sitting in there,  the dual belts,  and I'd have to 
 RJT> change all of that,  and the PS pump to get it to a non-A/C 
 RJT> setup.  So I just left it in there.
 MMC> .............................

 RJT> I'm not sure,  but I *think* that on this one the blades tend to 
 RJT> flatten out at higher speeds,  using less power.

 MMC> AND riveted on.  Those types were the major targets of the "flying
 MMC> fan blade" warnings that Charles brought up.  Some or many of 
 MMC> those had the rivet holes punched cold, causing hardening of the
 MMC> metal around the holes. With the flex tip added on, the rivet 
 MMC> holes would begin to crack from the continued flexing at the rivet
 MMC> points.

 MMC> I'm sure they've solved that problem now, but you've got older 
 MMC> equipment that falls within that time frame when all the warnings
 MMC> were issued.  I would recommend checking for any signs of cracks,
 MMC> such as rust from a loose rivet or a crack, using a good light and
 MMC> mirror every few years.

Well,  the last time I had that stuff apart was when I put a new water pump
in there,  last summer?  The old one was an interesting thing to see,  as
much of the impeller was just *gone*.

 MMC>> Then came the fan clutch, some thermal controlled, and some RPM
 MMC>> controlled.  A good idea, BUT!  It ended up with too much 
 MMC>> spinning weight on the two puny bearings built-into the water 
 MMC>> pump, and a LOT of premature water pump failures, which if not 
 MMC>> recognized by the owner (seldom) often resulted in the entire 
 MMC>> water pump shaft failure.

 RJT> Those setups were built into the water pump?  I've never had one 
 RJT> of those,  and was of the impression that it was in the fan hub...

 MMC> They ARE in the fan hub, but bolted onto the very END of the 
 MMC> water pump shaft which IS the inner race of the water pump ball 
 MMC> bearing. In effect, they are adding a bunch of weight extended to 
 MMC> the TIP END of the water pump bearing, which it was never 
 MMC> designed to handle.
 MMC> .....................

Ok.

 MMC>> "nearly ideal" as they could now slow the water pump
to reduce 
 MMC>> cavitation wear on the impeller, reduce the load on the water 
 MMC>> pump bearings, and at the same time increase the speed the fan 
 MMC>> even more to get the needed airflow.

 RJT> Dunno if it was "cavitation wear" or not,  but when I changed out 
 RJT> the pump last time around there wasn't much of the impeller 
 RJT> left!  There were nontrivial portions of that sucker that were 
 RJT> just *gone*.

 MMC> That could have been a combination of cavitation and corrosion. 
 MMC> Cavitation wear usually shows up as pinhole bubbles on the back 
 MMC> surface of the blades, and it 'grows' until there is no blade 
 MMC> left.

 MMC> Wear from dirt and rust particles will show up on the front side
 MMC> of the blades. 

 MMC> A combination of BOTH eats blades pretty fast!   :-((

I guess.

 MMC>> Of course, ALL of this could have been solved by installing a 
 MMC>> larger or thicker radiator.  The last "big" car I
owned had the 
 MMC>> hugh shroud, a seven-bladed fan with stainless steel 'blades' 
 MMC>> riveted on, and a thermal controlled fan clutch.

 RJT> Every time I've mentioned the idea of switching to that sort of 
 RJT> a fan people have talked me out of it,  saying that I'd end up 
 RJT> with more trouble than it was worth.

 MMC> VERY TRUE!  Avoid it!   :-))

The consensus holds,  then.  :-)

 MMC>> I noted that the radiator had three rows of water tubes, but the 
 MMC>> tanks had positions for five rows of tubes, two of which were 
 MMC>> never used.

 RJT> I've noticed that about some of them too,  what a waste!

 MMC>> If the radiator would have been built to use all five rows of 
 MMC>> tubes, I probably could have gotten rid of the shroud, clutch, 
 MMC>> and reverted to the simpler four or five-bladed fan at a slower 
 MMC>> speed.

 RJT> Didn't you have an option for a different radiator in there?

 MMC> Probably was such an option, but I always wondered why the FULL
 MMC> radiator wasn't used in the first place.  THAT car was no
 MMC> 'cheapie', and the sticker price to do that when it was assembled
 MMC> probably wouldn't have been $10 different. 

Heh.  Manufacturing economies...

A new,  heavy-duty radiator and fan shroud is on my list of what that truck
needs.  So's a little body work (rot over the rear wheels),  and I need
that done and to work on the parking brake (frozen cable) before it'll pass
inspection again,  and it needs painted.  Then I start worrying about the
interior,  and prettying it up a bit.  But that comes after I'm back
employed again.  And of course when the weather is conducive to working on
the darn thing,  which we're headed _out_ of.

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