I have a 94 f150 5.0. My temperature gauge fluctuates. When I am idleing the temp will climb to about 1/4, then when I get on it it will drop is this normal. I just replaced the thermostat today. And there is a gurgling noise from under the dash or the floor board. It sounds like liquid moving around. Is that normal.

 

You will probably need to check and add coolant a couple more times. Take the cap off and let it idle until stat opens....also turn on heater....and keep adding coolant until it is full. Shouldn't gurgle...that is air in the system, but it is normal for the gauge to move up and down with tstat opening and closing.

 

Do you have manual trans? That sound might be your fluid splashing around, mine sounds loud as my insulation under my shift boot is gone.

Is your coolant level remaining the same?

 

It is an automatic transmission I thought that might be what it was but I wasn't sure. The coolant level has not been staying the same but I just replace the thermostat so it's not quite full yet. and I can't find any leaks but I don't have any symptoms of a blown head gasket. I was told it could be a leak behind the water pump on a small hose that is really hard to get to I haven't looked there yet

 

I would think if your water pump or hose coming from, was leaking, you would see water dripping.
Try (while engine is cool) parking front end uphill and remove rad. cap and start engine, while getting up to normal operating temp just keep adding coolant. That should what they call burp the system and get all the air out.