DeTomaso Mailing List: May 99, Message #76

Dan,

Thermodynamically, it shouldn't matter except that the air flow may be
better top or bottom (don't know which, but I'd guess the bottom) but
that's a second order effect anyway. Practically, you want it consistent
with the thermostats. Also, since you can't switch it at the engine end,
and the radiator end "up tubes" are really sized to fit one way (right tube
to top, left to bottom at least on my car), seems like there isn't any real
choice. From a bleading standpoint, it might be better to have the input on
top so the air goes right to the vent.

The early cars (mine) had a vertical baffle (front/back flow) and one
thermostat. The water from the engine went throuth the left tube to the
bottom radiator tube (which I think connected to the front of the radiator)
and hit that thermostat after going through the radiator (I think, and it
makes sense). 

The later cars had a horizontal baffle. There is a high temp and a low temp
thermostat. The way I believe it is supposed to work is the high thermo
senses the incoming water and is slightly above the engine thermo temp. The
low thermo senses the return water (measuring how much cooling has been
done). When the out temp gets too high (158 deg), the second fan comes on.
HOWEVER, PPC's (Lary Stock's) online parts catalog (www.panteraparts.com)
calls out just the oposite. It calls out 158 deg Primary Fan (Upper) and
185 det Secondary Fan (Lower). But then the diagram clearly shows the
engine output (from the tank) going in the left tube and up to the radiator
in "19 Pipe lower radiator front". That would be connected to the 185 deg
thermo. Some may argue, but I would call this the primary, since once at
temperature it will almost always be on, but the outlet temp will often be
40 or more deg cooler.

So, I would say put it back. Don't try to switch your thermostats, there's
a good chance you'll snap off one of the studs and you'll be in real
trouble. I'm not sure how you got the pipes to fit and it must look a
little strange. 

The improvement you saw must have been from something else because your
lower (185 deg) thermostat and fan should now be off most of the time - the
engine temp would have to be 215 to 230 to turn it on which should have
made things worse. Of course, if your is running hotter than that, both
fans would be on all the time and it shouldn't have made any difference. Of
course, your car SHOULD be running at around 180 - 190 if you have a good
radiator and (after market) fans.

Anyone know any different??

Richard Barkley