I have had my 2004 Suzuki xl7 ex3 for 8 years with little problems. I put a radiator on it three years ago because I was in a fender bender and got a slow leak. (crack on top)

I also had a pulley idle issue. 

Last wedit over heated as I was pulling into a parking spot and of course I got towed We filled the fluids and ran idle and checked but no incidences. So I went on a short trip and it did it again right after I pulled into a parking spot.

There are two similarities I noticed. In both caes I was incidentally driving on third gear by mistake,  and shifted to drive during motion. (I've done this before) and two I think I accelerated. These were directly prior to the temp gauge needle elevating.

Also at least on second incidence inspection my resvoir tube was disconnected. (did it explode off or was it just loose in there have no clue)

My ac is not working  for most of  7 years and I quit trying to fix it 

There is no leaks I can find. There is no white smoke.  The oil is clear. There is a squealing serpentine belt which I wondered if the  "infamous pulley idler was acting up again" ..   Could that cause a pump issue? 

Well after the second overheat, tried to get home after cooling and reconnecting the reservoir tube,  the reservoir was of course full of hot water lol  and again towed sat.  

In eight years I haven't changed the rad cap or thermostat, so guess I'm starting there and do a coolant flush clean and sealant while I'm at it

Also you mention bars leaks repair sealant and steel seal. which one is better for me?

Nothing bad about the oil, will also do an oil change...

Trying to get this car stable may need a few tests by a mechanic. Haven't run it hot  for more than a minute in all cases.

I can't afford a newer car. this is paid for and all I can do. How to diagnose this issue, eradicate it and keep the car not getting ripped off by a mechanic is my goal. 

I really have enjoyed this car.

please help.