Just finished an engine-out HG job and did everything as documented using OEM HGs and seals, etc. Upon first start, we soon noticed engine was beginning to overheat and overflow bottle filling up. My suspicion would be air in system and/or faulty thermostat.
After bleeding system we couldn't fix it so quit for the night. Next day I extracted fluids for inspection and it all looked good. I decided to run without a thermostat. First test run car reached proper temp after a 15 minute warmup and I ran about 10 miles with perfect temp, coolant overflow bottle level, and no air bubbles. Conclusion: HG job is good and car is running great, must be bad t-stat. I then did a boil test with that t-stat and it appears to be OK, although I was hoping to find it bad.
My question is how open should a fully open t-stat be? Mine tested at about 1/4 inch between the mating plates when fully open. Is that enough or should it be more? T-stats sticking is just not something I ever think is real. I figure they are either good or bad. Thoughts? Thanks !!