This one stumps me. I've always had kind of a marginal problem with the
engine overheating in the GT6 (surprise!!) so I thought, before heading up
to San Bernardino for the Route 66 show in a few weeks, in the hottest time
of the year, I would clean, back flush, and refill the system. Being
rather HOT this week (almost setting a few records, with highs over 100),
and seeing the temp gauge within an 1/8 of an inch from the red, when I
drove it last week, I figured it couldn't hurt.
A little background first. Rebuilt from the ground up in 1989. Engine
completely rebuilt, but not hot tanked. Radiator core replaced with high
efficiency one, excellent job, even tried Water Wetter, with very little
antifreeze (didn't notice any appreciable change). Working 180 deg.
thermostat. Stock type oil cooler installed, timing correct for engine,
currently at 12 deg before, with working vacuum advance. Doesn't knock or
ping using regular 87 octane. Runs great, stock 8 blade plastic fan (don't
want to replace with electric), with proper shroud in front of radiator.
Has run hot at idle ever since I've had the car. Only runs hot at speed
when it's very hot outside (over 90 deg), so I figure it's an airflow
problem at best, since it always ran hot only at idle or low speed
conditions. I bought Prestone's Super Flush, and following the directions
drained the system, refilled (with Super Flush and water) and ran the
engine. The directions state to run at temp for 10 min. I figured since
it was around 95 deg outside it would warm up pretty quickly and this
wouldn't take too long. Started it and ran it for a good half hour. NEVER
got anywhere near overheating. Just registered slightly over the half way
mark when I shut it down. I have not drained the flushing agent out yet,
just ran the initial flush through the engine, and haven't even refilled to
ensure that all the air is out of the system. Now I realize that under load
that the engine will generate much more heat, that has to be dissipated,
but If what I saw with this is true, then this car should never run as hot
as it does. It should cool down at idle which it never has, unless it's
cold outside. What am I missing here? You could never idle the car for
more than 15 minutes without it almost boiling over on a day like this,
even with the heater on (been there done that) - I can't believe that the
Super Flush is the cure, as I haven't drained it out yet-I wish it would
always run this cool-why would just Idling in the drive way not cause an
overheating condition, but after running on the road, and then letting it
idle it would overheat? By the way, it would not register hot while
running on the road, until after you slowed down at a light and sat for a
while, then it would slowly creep up unless you got moving again. It's got
me stumped-
Barry Schwartz (San Diego) bschwart@pacbell.net
72 V6 Spitfire (daily driver)
70 GT6+ (when I don't drive the Spit)
70 Spitfire
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