Hello. Have a 91 hatch obd1 b20b. No leaks, flow is good, block was flushed. Waterpump works. Thermostat opens and closes. Fans work. Block tested for combustion leaks, its negative. The catch is If its sit in drive way it wont overheat, until..i drive it then engine overheats. It will go to half then will slowly spike up to H if i let it. Then i would have to turn it off to cool down.. compression test are equal all around 160 psi on all 4. No milky oil or dirty coolant. Dont see level dropping either, no smoke out of tailpipe. it will still overheat.
Suspecting a headgasket but trying find solid evidence.. any input would help thanks for reading