I have a '99 F-150 which has some type of coolant leak. It seems to develop from the upper radiator hose (still in good shape) or into the reservoir where the hose goes into. I have also found coolant on top of my #4 COP. Now.. I was wondering if maybe there is a small hole in the back side of the radiator since the hose is good and it might be spraying back towards the #4 (causing a misfire at times). I was thinking of adding bars-leak to the radiator (I'm getting desparate) and was wondering if there would be any side effects by adding this gunk to the degas bottle. Any advice would be helpful.

Thanks in advance!

 

As far as the leak above the #4 plug, Check the heater hoses. These are a known problem for leaking. Replace the POS ford hose clamps with the screw style clamps.
You can also go and rent a Coolant Pressure Tester from an Autozone. Pump it up to 16psi and you should be able to pin point the leaks.

 

Hey, my dad's truck, also a 99 f150, had the exact same problem, but the coil pack for the number 4 cylinder shorted out from the coolant, and the cylinder stopped fireing. We took it in and had a new coil pack installed and the hose was replaced. So if your cylinder is misfireing, there is a good chance it may stop due to a short in the coil pack. Try to fix the leak, other than that your on your own. All i know it it idles really rough running on only 7 cylinders, and boggs down when you hit the gas. It may sound fine running at a certain speed but it won't when idleing.