Have replaced radiator cap. 1 qt. of Coolant disappears after 100 miles. Temperature guage indicates overheated condition, but no biol over occurs. No coolant leaks can be seen.
You Are Probably Leaking Coolant Inside The Engine.
You can’t see it leaking because it is leaking into the combustion chambers, turning into steam and going out the tailpipe.
You may need new head gaskets. I wouldn’t drive it any more until this is verified and repaired. Additional damage could result.
CSA
Sounds like you may have a leaking head gasket. Don’t guess, however, because there are tests to verify this condition. Get it checked out to be sure. Overheating of the engine can cause even more problems.
From what you state these are signs of a bad head gasket I’m sorry to say. Have a block check done to see if exhaust gases are getting into the coolant. They may be and that is causing the overheating.