I have a 1997 scab 4.6 I'm having trouble with my heat and temp it will warm up and when I'm on the throttle stay at the the running temp but when I let off or idle it drops down I changed my thermostat didn't change anything just trying to figure out what is wrong with it please let me know?

 

And sometimes it will go up over 215 and then drop back down

 

Are you sure all the air was purged from the cooling system? If you see an immediate change in temp coming off idle I think that could be a cause.

 

Yeah I got to looking at the anti freeze it hasn't been changed in a long time I think it's old and weak and that might be my problem

 

I'm pretty sure you're water pump has gone bad, I had this issue with over heating on highway and would drop with low rpms for a period of time , my coolant hadn't been changed in so long it was already brown n rusty which at this point is so acidic it eats away at the metal propellers on the water pump causing there to be no flow/pressure for the coolant to move completely through the system. As you can see mine was pretty bad, hope this helps

 

How hard was it to change the water pump?

 

you got to take the air intake off, fan , fan surround and the top hose for the radiator and the belt. 3 bolts on top 1 at the bottom might have to hit it with a rubber mallet to get it off make sure you have a good sized bucket coolent will go everywhere this is on a 2003 5.4 and my waterpump was $40 at autozone

 

Depends on your comfort level of digging in, it's a lot easier than what it sounds to be honest there's a thread on the forum somewhere that I used and a YouTube video that shows the process on a similar engine I think the video was done by a1autoparts only took me a few hours but that's because I changed my lower radiator hose and spent extra time flushing the block n radiator to clean all the old nasty coolant. Difficultly out of 1-5 with one being the easiest I'd say a 2.5 tops

 

Thanks a lot guys you really helped me out here!!