Right answer, but the reason given is a common
misconception. The more flow in a system, the more
heat transfer will occur. However, with too high a
flow rate (that is, beyond the design's intent) there
will be high fluid velocities and poor distribution
of the coolant, and there will be hot spots. This will
happen in the distribution header of a radiator, and
is why a good radiator should be sized for low
velocities in the header (large area relative to the
tubes so that the ratio of velocity pressure to total
pressure is low).
--- Bruce Lowry <egnorant@flash.net> wrote:
> My guess would be the gutted thermostat. Water may
> be sailing through the system
> too fast to absorb the heat properly. When it sits
> it soaks up the heat and acts
> up. Learned this from an old mechanic who was a bit
> crazy but he was a great
> mechanic.
> Bruce Lowry
>
> KGROWLER@aol.com wrote:
>
> > My '79 1500 Midget has had problems lately with
> sudden overheating and
> > burping coolant into the overflow tank.
> >
> > Background - About 98000 miles on the car.
> Radiator was recored 2 years ago.
> > Water pump and fan clutch replaced last year.
> Running with a gutted
> > thermostat in place. It runs on the hot side in
> hot weather and I have at
> > times had to use the heater system for auxilary
> cooling when driving at
> > Interstate speeds. It runs hotter at higher
> running speeds, will usually drop
> > back down at lower speeds.
> >
> > The problem - I have had 3 sudden overheating
> situations in the last two
> > months. The first time it happened was on the way
> home from Twist's after the
> > car was shut off for a few minutes at a gas stop.
> We had gone about 150 miles
> > with no problem, then after the brief shutdown to
> gas up, it immediately
> > climbed into the red as I reentered the
> Interstate. The other odd
> > circumstance was that the heater fan was on when
> the temp started to climb,
> > but the air from the heater outlet was blowing
> cool air, not the very hot
> > air I would expect from an overheating engine. I
> pulled off as soon as I
> > could. The only sign of heating was a small amount
> of oil bubbling under one
> > side of the valve cover and there was about 1 pint
> of antifreeze blown into
> > the overflow tank. After about 45 minutes, the
> temp gauge was down
> > considerably and we wnt the rest of the way home
> on surface streets with no
> > problem. The second time it happened I had not
> stopped or shut down the car,
> > it just started climbing while we were about 30
> miles into a 40 mile trip on
> > a 50 degree evening. Since then I have refilled
> the system with the front
> > raised thinking it was an airlock but still had it
> happen again last weekend.
> > I was heading for RoadAmerica when it did it for
> the 3rd time. It was only
> > 50 degrees out, the car was running fine when I
> stopped to reclip a couple
> > Tenax fasteners on the top. I shut down the car
> for 30 seconds to jump out
> > and fasten the top. When I restarted and took off
> again, the temp gauge
> > immediately climbed to the red. Letting it sit for
> 1/2 hour got the temp down
> > to 1/3 of the way up the scale and I turned around
> and drove back home with
> > no further problems.
> >
> > Any ideas? The cool air from the heater outlet
> when it happens throws me. I
> > am about to pull the engine for a 100K rebuild but
> the spare engine is still
> > not ready. I'd like to drive the car to the NAMGBR
> AGM in St.Paul in two
> > weeks but not if I don't figure out what is going
> on here.
> >
> > Kim Tonry
> > Downers Grove, Illinois, USA
>
>
=====
Ron Soave
"You Are What You Remember"
1960 Bugeye
1972 BGT
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