Mine has been doing this from day 1 more than 2 years and 28k miles ago. The way to tell is drive it, park it over night and next morning squeeze the upper radiator hose and see if its heavily pressurized and open the reservoir cap. Does it hiss when you open it the next day? In order to mitigate the problem and extend the life of the head as much as possible, I put a lower pressure reservoir cap off a 190e (forgot the pressure rating) and a colder thermostat (71c I think) and and switched to electric cooling fans ONLY which are turned ON at 82c. Its never gone to 100c and only very rarely climbs about 90c in extreme load /heat situations.

You can probably keep driving it for a long while if its not consuming coolant or mixing oil/coolant but eventually you will have to do something about it. Start hunting for a #17 and up cyl head and put it on your long term projects lists. I have the #17 head waiting in the garage. One of these days I'm going to get to it. Its running so well on the #14 head right now I really don't want to mess with success. 202k miles and counting.

Oh on the cost of the head... they seem to have gotten more expensive lately after people realized they're in demand. I paid $700 2 years ago for my #17 completely with everything (cam, lifters, injectors, headbolts etc). Its still sitting in the shipping box in my garage. I've seen people asking $1000+ for a bare head lately. Highway robbery.

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CENSORED due to not family friendly words