GT5OH <goldandjewels@gmail.com> wrote in news:1184887011.843213.203590
@x40g2000prg.googlegroups.com:

Air pockets in the system, perhaps?

Time for a new rad?

Buy a Mister Gasket 190degree stat and try this first.Maybe rad needs
unplugged?

Here are the a few things that can cause overheating that come to mind:

1)  Air in the cooling system.  This is more probably after draining the
system and refilling.  Usually driving will work out the bubble.

2)  A bad water pump.  Typically there will be a leak present but not
always.  With a bad water pump the car will usually overheat under all
driving conditions.

3)  A bad clutch on the fan.  This will usually cause overheating in
stop and go driving but not during highway driving.  At high speeds the
there will be sufficient air moving through the radiator to cool the
coolant.

4)  A clogged radiator.  This will usually cause overheating under all
driving conditions, especially stop and go driving.  Sometimes you can
feel the return side of the radiator and find it abnormally cool.  Also,
an infrared laser thermometer can show hot and cool spots through the
radiator that indicates inconsistent cooling and thus a clog.

5)  One last thing that comes to mind isn't a good one, a blown head
gasket.  If this is the case most times you will find oil in the coolant
or coolant in the oil.  Not always though.  The leak can be small and
only occurring under combustion at high pressure.  In this case the
combustion gases get into the coolant, heating it and causing air
pockets.  There are paper strips some shops use to detect the presence
of hydrocarbons in the coolant.  They are very sensitive and can tell
you a head gasket leak is present when there are no other symptoms.

There is a trick you can use to help diagnose if it is a clogged
radiator or clutch fan.  When it overheats turn the interior heat on
high and the blower fan on high.  If this drops the temperature some
then I put my money on the clutch or the radiator.  Then if it doesn't
overheat at highway speeds I say its the radiator.

I have used the heater blasting at full speed in the summer more than
once to limp home without boiling over.  It is amazing how much this
will help cool the engine.

Also, make sure the reservoir is filled to the full mark.  Check it, and
top it off if necessary, until it stabilizes.

Hope this helps.

Just a couple thoughts.  I'm also just a mid-level hobbyist, so
someone else might have better input...
First, I'd wonder about the thermostat.  They do wear out and
eventually fail, and that would cause your problem.  If you have a
Chilton / Haynes book, you CAN replace a thermostat yourself.  On this
motor, they're a pain in the !#@%^# to get to, with some hoses in the
way, but if you could replace your radiator hoses, you can do this.
Next, anytime the coolant system is 'compromised' ie loses coolant,
takes in air; you have to 'burp' it, or purge the air. Basically, if /
when coolant leaked, air took it's place.  When you refilled the
radiator, an air bubble was 'stuck' somewhere and the net effect is
that you're low on coolant, even after topping it off.  Also, when you
tested it, realize that driving on the road, presumably with the A/C
on puts more load on the engine and also generates more heat. To
'burp' it, make sure it's parked completely level, or even with the
nose slightly high, so the radiator cap is the highest point on the
system - air will work its way to a high point. Turn it on, put the
heat on high, and let it run.  Check every 3 - 5 minutes, and top off
the coolant when the level drops.  I usually do this over about a half
hour.
Other thoughts would be the fan clutch (I've had them go bad on two
Fox-body 5.0's), or transmission trouble, if it's an automatic
(although that's a long shot).