Over heating problem

[MacDiesel]

i have a 98 cobra and it has a wierd over heating problem. when i hop in it and start driving the temp gauge stays on cold until i drive for about 5 or 10 minutes, and then it goes up gradually all the way to the farthest point of the normal. then it goes back to where it should be. i could drive for an hour and the gauge never moves again. it only does it when i first get in it from a cold start. i changed the thermostat and coolant thinking that the thermostat was just sticking, but obviously wasn't it. does anyone have any ideas?

 

[EightyFoFiveOh]

Does it have ducts that direct air from over the exhaust manifold into the intake on cold starts? If so, it may be that they aren't closing when they're supposed to and blowing hot air in the motor after its already warm.

Just a thought...

 

[Railroad]

Does it have ducts that direct air from over the exhaust manifold into the intake on cold starts? If so, it may be that they aren't closing when they're supposed to and blowing hot air in the motor after its already warm.

Just a thought...

WHAT !!!!!

It's just the thermostat. You may want to drill a small hole in the flange
and orient it toward the top. Some stats already have this hole.
In my F150 the gauge goes up and down a couple of times before
the coolant temp is consistant.

 

[EightyFoFiveOh]

---If what Railroad says DOESNT work...it may be a radiator hose collapsing, the laminate inside the hose can collapse and restrict flow without any signs on the outside at all.