1999 Ford ranger overheat issue

What is your question?

Changed everything on 199 Ford ranger as far as cooling goes . Runs fine on startup w/ AC on. Drive it down the road,runs fine,but the first time I slow just a little ,temp start to rise toward hot. The only way to get it to start running co heol is to accelerate up to 70 or 80 mph or shift to neutral and rev for about 10 seconds. No water leaks visible. Does I have air in my cooling system. If so is this causing my problem.

What makes this problem better or worse?

When hot

How long has your 1999 Ford Ranger had this problem?

Few months