OK any ideas on this. I replaced the thermostat, flushed the radiator and have the same problem. it can idle just fine but it gets hot driving less than 15 minutes There are no visible leaks.
First question: are the cooling fans coming on?
If not, have a mechanic check:
Clean the fuse and relay contacts even if they seem OK
In short, there are a whole chain of components that must all be working properly in order to turn the fans on. Any one of them not working can cause the fans not to turn on.
If fans are coming on, then other possibilities are:
Bad water pump (vanes eroded)
Leaking head gasket
Just because you flushed the radiator doesn’t mean it isn’t plugged.
Usually when going down the road the radiator fan doesn’t need to come on, especially if it is cold outside where the OP resides, which seems likely. My first suspect is either there is air in the cooling system or you need a new radiator cap. It may be loosing pressure due to a faulty cap. I’d replace it with a new one, see if that fixes the problem. After that re-bleed the air from the cooling system. Still a no go? Then a pressure test of the cooling system is in order. If that passes, a visit to the local radiator shop where they can run an assortment of other tests and will likely determine the cause straight away. You may just need a new radiator. But I’m guessing all you need is a new radiator cap.
This could be an indication of a breached head gasket.
With the engine cold remove the pressure cap from the coolant reservior. Start the engine and while it’s idling watch the coolant in the reservior. If bubbles start to form in the coolant that’s an indication of a breached head gasket. Now have someone bring the RPM’s up. if the bubbles form at a faster rate, that’s a blown head gasket.
I have had a few instances of the water pump pulley getting really slick so the belt slips, I sand the shiny metal with 80 or 60 grit sandpaper.
Found out it’s a warped head.