1
Our subject vehicle is a stock and largely original ’86 GT with less
than 100,000 miles. It’s been a while since the cooling system was
inspected and serviced. Considering the age of this car and that
5.0s tend to run hot, it’s the perfect opportunity to tackle this project.
With the help of technician Geoff Vassell at DaSilva Racing, we got
to work.
3
As rubber ages it becomes less flexible, breaking down and
eventually cracking. Look for signs of swelling at the ends of each
hose. If you see this and the hose feels soft when you squeeze it,
it has likely collapsed internally and needs to be replaced. Even if
the hoses are still in reasonably good shape, it’s cheap insurance
to replace them.
5
2
Before you start, it’s a good idea to take stock of what needs to be
replaced. Inspect the upper and lower radiator hoses, as well as
the thermostat bypass hose and the heater hoses that run from the
back of the block to the heater core. It’s not uncommon to find the
heater core has been bypassed, almost always because of internal
corrosion circulating in the coolant. This is an indicator that other
aspects of the car have been neglected, too.
4
V-8 and V-6 engines have a single serpentine belt. Small cracks
running parallel to the ribs on the inside are normal wear. If there’s
anything more, or if there’s damage to the outside, the belt needs
to be replaced. If you’ve owned the car for 10 years and haven’t
changed the belt, it’s due, even if the Mustang hasn’t been driven
much. Four-cylinder cars, including turbos, use conventional fan
belts, though the same rules of thumb for inspection apply.
Our cooling system appeared to be in good working order, though the
antifreeze was several years old. Over time, antifreeze loses its boiling
properties and corrosion inhibitors. For the typical 50/50 water/ethylene
glycol mix, it’s a good idea to flush and refill at least every three to four
years to prevent internal corrosion and lime-scale buildup. Some owners in
hotter climates, or drag racers, run a 70/30 mix or even pure water topped
with an additive like Redline’s Water Wetter. If you run water and live in a
cold climate, remember that frozen coolant can crack the block or heads.
Issue 7 FOX Mustang Magazine 35