Overheating Problem

["Christopher Ritchie" <critchie1@hotmail.com>]

Leif Pedersen wrote:

>If your '92 100 is set up the same as my '87 5ktq I would change the
>thermostat ASAP.  I had similar warnings, occasionally the indicator 
would
>flash due to low coolant (when the level should have been adequate), 
and
>the temperature had just started to run slightly higher then 
normal.  300
>miles from home, cruising at 70 mph, my engine started to ping 
lightly
>going up a hill.  No over temp warning, just slightly above normal 
coolant
>temperature.  Slowed down a little and pinging went away.  By the 
time I
>hit the next hill it was too late, coolant steaming out all over.  
Blown
>head gasket and cracked head.

>I wondered for a while on why I did not receive more of a warning.  
When I
>inspected the thermostat, it had failed shut!  With boiling water on 
the
>stove it did not open even a little bit.  First failure that I have 
ever
>had like that.  Without coolant circulating through the engine, I do 
not
>believe that I was reading the correct engine temperature on the 
gage.
>Everything seemed almost normal, but the engine was running a lot 
hotter
>then the gages were telling me.

 
The thermostat fails shut; the engine boils over; and,  the 
temperature gauge reads "just slightly above normal"???  No Auto-
Check warning???  
 
I have always wondered about the coolant temperature monitoring 
system in type 44 cars.  After warm-up, my temperature gauge ('88 
5KSQ) will vary between the 1/4 and 1/2 mark, depending on 
conditions.  When the gauge reaches the 1/2 mark, the fan will come 
on, lowering the gauge reading.  I understand that this is normal.  
But a thermostat is supposed to keep the temperature of the coolant 
in the block at a designated temperature.  Engines are designed to 
operate best at a specific temperature.  Where the gauge rises and 
falls, this leads me to believe that the temperature gauge is 
monitoring the coolant in the radiator and not the block.  This would 
also explain Leif Pedersen's experience.  Is this so?  Am I missing 
something?  This is nuts.  You would never know if your thermostat 
failed.      

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