Hello everyone,

About 7 years ago I flushed out the green coolant in my 1991 Chevy
K1500 pickup with a 4.3 V6. The truck now has about 97,000 miles on
it. Normally, I would say stick with whatever coolant came from the
factory but the orange coolant seemed like a better choice at the
time. I liked the fact that it had a 5 year or 100,000 mile life, and
the container said that it was easier on water pumps. It was also
ethylene glycol based and seemed to be very similar to the green
coolant so I figured why not try it. After flushing the green coolant
out, I replaced it with the orange coolant (I think it was texaco) and
mixed with distilled water.

My water pump recently started leaking, I don't think it was the
orange coolant, just age. I have not had any other problems with the
cooling system, but I have recently heard some bad stories about the
orange coolant causing head gasket damage, intake gasket damage, and
water pump damage, on some vehicles. I've also heard stories about the
orange coolant "sludging up"  but I have not noticed that problem yet.
On the back of dexcool containers, it says the coolant is for use with
1994 or newer vehicles and that on some vehicles (mine was not listed)
if you did not change the coolant at least every 2 years, cooling
system damage could result.

I'm going to flush the system & replace the water pump, upper and
lower radiator hoses, thermostat, and radiator cap. Should I keep
using the orange coolant or go back to the green coolant ? I would
stay with the orange if I new it would not hurt anything, otherwise in
the absence of an answer, I am inclined to go back to the green stuff,
providing it won't do more harm than good.

I'm not sure why GM specifies 1994 or newer vehicles and I tend to
wonder what the difference would be between a 1994 4.3 V6 & a 1991 4.3
V6 ? Are the seals or metals used different ? That's about the only
think I could think of that would make a difference.

Is there anyone out there from a GM service department that knows the
answer ? I'm hoping a mechanic or GM tech may be able to answer this
question with a reasonable degree of certainty.

Thanks for your help.
John