2008 ford ranger 4x4 with the 4.0l v6 just had the thermostat housing replaced with the metal upgrade last week and today on my way home from work the temp gauge went up into the red so I pulled over immediately then checked under the hood no leaks oil looked okay no white smoke from exhaust heard gurgling from near the upper radiator hose. Let cool down to half way and limped the 5 min drive home over 45 mins pulling over when it reached close to red. Could it be air or bad thermostat??

 

You most likely have air in the cooling system. Check the radiator level when it is cool.

 

Update: Idled it with the rad cap off till it got to operating temp this morning. then as soon as i start driving it like within a minute the temp gauge started to climb up so i stopped and pulled over back at home. could I have gotten a faulty part they used a metal replacement but idk which brand

 

since you did not do the work yourself it's always a guess as to the quality of the parts and the skill of the mechanic. I'd guess a bad/cheap/incorrect thermostat or air in the coolant system that needs to be burped

 

A well known member here has suggested filling the 4.0 via a heater hose.
There must be something to that.

How does one release the clamped hoses from the heater core nipples?
Is it just a suitable screwdriver worked into the crimped part?

 

Or park facing uphill, so any air can find its way to the radiator cap.

 

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