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Jim Grant's Tech Tips
'92 Dodge Caravan, Overheating Problems
Q:
I own a ‘92 Dodge
Caravan, 3.3l V6. It overheated on my daughter, and she drove it perhaps
5 miles with the check gauge light on. I found a hole in one old hose
and replaced it (the one entering the block just below the water pump,
the hard one to get at. ). After refilling with just water, the engine
runs at normal temp for about 10 minutes, then immediately goes very hot.
I noticed that the interior heater did not put out warm air. I checked
the water lever and found that after it had cooled down it had lost considerable
water, but not externally. The oil seems to be waterless, so I am wondering
where the water could be going. I do hear a boiling sound from the engine
about 20 minutes after engine cutoff, but that seems to be in the vicinity
of the overflow tank. It’s a mystery to me. I also have noticed that
the air cooler fan does not operate when the water is over normal temperature.
What would you suggest?... John Richard
A:
I’d
say your daughter went a little too far with the warning light on. At
this point you have described, almost perfectly, the symptoms of a failed
head gasket or cracked cylinder head. This condition allows air pockets
to form in the cooling system from the combustion process and coolant
to escape via the exhaust. If you snap the throttle just right I’m
sure you’ll get a good cloud of white smoke from the exhaust. There
are a couple of ways to prove this failure. There is a chemical that reacts
(changes color) to the presence of CO2 in the cooling system. CO2 just
happens to be a by-product of the combustion process in an engine. If
a reaction occurs the engine has to be disassembled. Both cylinder heads
should be removed and inspected for gasket failure or head damage and
serviced as needed.
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