Phil wrote:
You probably have an internal coolant leak inside your engine. The
coolant is escaping into the combustion chamber or crankcase through
cracks in the cylinder head or block, or through a leaky head gasket.

In rare instances, coolant may also leak into the automatic transmission
fluid cooler if one is located inside the radiator. But usually when
automatic transmission fluid leaks into the coolant it means the line is
leaking.

Pressure testing the cooling system is necessary to diagnose an internal
leak. A cylinder leak-down test can tell a mechanic if the coolant leak
is in the combustion chamber. But to pinpoint an internal leak, it is
usually necessary to remove the head(s) from the engine. The head may
then be pressure tested and/or checked for cracks using special
equipment.

Minor internal leaks can sometimes be temporarily sealed by adding a
sealer to the cooling system. But large leaks or ones that do not
respond to a sealer will have to be fixed.

If the problem is a cracked head or block, repairs may or may not be
possible depending on the nature of the crack. Cracks in aluminum can
often be repaired by welding while those in cast iron can be fixed by
pinning the damaged area. But some cracks may be so bad that they are
beyond repair or in a location that makes repair impossible. In such
cases, the head or block must be replaced.

If a leaky head gasket is the culprit, replacing the gasket may only
temporarily cure the problem if the head or block is warped. The mating
surfaces on both the head and block should be checked for flatness and
resurfaced if necessary to restore flatness for a proper seal.

Hope this shed some light for you.

--
Regards
Dan.
00 VX SS 273 Rwkw of unforced mumbo.
All throttle no bottle.