Where are the glow plugs on an 03 f350 with the 6.0 diesel?

To add further to Simon J P's excellent answer, 2003 model years use what is called a glow plug "buss bar". The second illustration on page 11 of the link below clearly illustrates its location. Bear in mind that if the cylinder in question is on the passenger side bank, you may need to undo engine mount(s) and/or loosen the heater box in order to enable removal of the buss bar without damage. Cylinders #5 and #7 are VERY difficult to access. Once the buss bar is removed, you'll need a deep 10mm socket and a short extension to access and remove the glow plug, through the rocker arm bridge.

Furthermore, 2003 model years use a unique EGR cooler (exclusive to 2003 model years) that are FAR LESS prone to EGR cooler failures, unlike 2004 to 2007 model years. Here is the 6.0L bible for you to download and save to your computer. Hope this helps.

http://www.forddoctorsdts.com/publications/ctb1/20...

Look on the bottom end of your cylinder heads located just below the valve covers. There is a harness with 4 individual connections for the glow plugs. If the harness was never updated then there will be a straight plastic bar with the harness contained inside of it. Are you sure that the engine hydro locked with fuel? Which cylinders? If it is the Rh bank be sure that it is not coolant. They are prone to this due to a faulty egr cooler.

Ford 6.0 Bible

they screw into the head. they pre-heat the combustion chamber, so the tip rests inside the combustion chamber.