Gosh, this sounds a lot like the problem I had with my old 84. I'm
guessing you have an air bubble in your cooling system...could be a sign
of head problems, it was for me, so keep an eye out. I'm sure others on
the list will have a much better, more detailed explanation.

Good luck, John.

Steve and Jo Ann Wacker
San Marcos, Ca.
90 Carat
86 Syncro