2001 E-150 4.2L Cooling Problem

Temp gauge pegs out and light comes on all of a sudden - it does this intermittently, but I swear it is not actually running hot. Even after driving it 10+ miles with the gauge pegged and the light on (I had no choice), CHT cutout never kicked in, no steam, etc. - just didn't appear to be running hot (you can usually tell).

I was initially thinking I had an air pocket or something, because I recently changed the bottom radiator hose, but now I'm leaning towards the sending unit or thermostat.

Coolant level is normal, no oil in coolant or vice versa.

I haven't had the van long, and it has new heads, so I'm assuming it ran hot before. Thus I'm a little paranoid about this.

It wasn't doing this before I replaced the bottom radiator hose (at least I never noticed it if it was).

Anyone ever see this problem before?

Now I'm back to thinking air in the system.

I drove it twice today. One for about 25 miles each way, and once for about 10 miles each way.

On the first trip, no problem on the outbound, but the needle pegged and light came on on the return trip - though it didn;t seem to be running hot.

On the second trip, just the opposite - needle pegged and light on on the way there, but no problem on the way back.

get it up to temp then take the rad cap turn it back to the first notch and let it up a little so it lets air go to the overflow tank dont let it out too much or you will have hot coolant all over you.

had similar problem with an old SUV

ya, ford engines can be tough to bleed sometimes. take the cap off of the reserve bottle, start the engine and let it run until the thermostat opens. then rev engine over 1500 and let the rpm drop do this repeatedly till coolant stops shooting out of the reserve bottle, refill bottle,close cap, and go drive vehicle. if the temp pegs again, down shift vehicle at higher speed and let full decel in each gear. this should force the air into the reserve bottle. return and recheck level.
hope this works. if not, get a vacula(think thats the name) and you might also have other problems. a t-stat is only about 10 bucks, try that too. much cheaper than an engine.