04 Nov 2003, 12:05, Roy J. Tellason (1:270/615), wrote to Matt Mc_Carthy:

Hi Roy.

 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...

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

 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.

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

Is that engine an inline 6?  What brand?

 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.

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

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

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 
 MMC>> 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.
.............................

 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.

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

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

 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 
 RJT> hub...

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

 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 
 RJT> out 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*.

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

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

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

 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.

VERY TRUE!  Avoid it!   :-))

 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?

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


     Good luck...  M.

--- Msged/386 TE 06 (pre)