Beside the point, but the '84 and '85 2.5 was never a closed system. The pre-91 Renix 4.0 (and 2.5?) had the closed system.
I had the problem you are having with my 2.5 bought new in '85 that I had for ~20 years. I don't recall temps early on but in later years it was pretty much impossible to get the temp out of the blue area on the gauge with the OEM setup.
I finally replaced the mechanical fan with a single Flex-a-lite electric fan and controller. (I wouldn't think you would need a dual fan setup.) Always had a 195* stat and 16# cap. This helped get temps up to a reasonable figure but I'm in a much warmer climate than you to start with.
Thought I would throw this out. Perhaps some other thoughts later.
I will add that I never, ever had a problem burping the system or any need to go to any special lengths to do so. Also, when the heater control valve rusted up, I replaced it but agree with just removing the thing.
I had the problem you are having with my 2.5 bought new in '85 that I had for ~20 years. I don't recall temps early on but in later years it was pretty much impossible to get the temp out of the blue area on the gauge with the OEM setup.
I finally replaced the mechanical fan with a single Flex-a-lite electric fan and controller. (I wouldn't think you would need a dual fan setup.) Always had a 195* stat and 16# cap. This helped get temps up to a reasonable figure but I'm in a much warmer climate than you to start with.
Thought I would throw this out. Perhaps some other thoughts later.
I will add that I never, ever had a problem burping the system or any need to go to any special lengths to do so. Also, when the heater control valve rusted up, I replaced it but agree with just removing the thing.