I just checked my coolant tank and found what looks like pea soup inside. Wtf! My F350 runs like a champ and it doesn't overheat. Should I flush the coolant? I'm worried its something more serious. Please help...... Any advice?
Sorry to hear this, and yes, it is serious. It sounds like the engine oil cooler has ruptured allowing oil to transfer into the coolant (due to the pressure differential of the oil and coolant systems). Oil is lighter than water (coolant) so it floats on top and settle's out in the degas bottle.
You have two options for repair:
1) remove and replace the existing OEM oil cooler. Upside: lower cost (~$350 for new cooler + gaskets, labor, misc. materials, etc. Downside: re-occuring oil cooler failurs are common, and either rupture or plugging (more common that rupture) is likely to reoccur in the future.
2) Upgrade to a Bulletproof Diesel air to oil cooler. Upside: one time fix; permanently separates oil and coolant systems; wont plug-up due to cooling system debris. Downside: cost; varies from ~$1,700 to $2,200 plus gaskets, labor, misc materials, etc.
I see you are San Jose. Left Coast Diesel (Concord & Livermore) or Devil Mountain Diesel (Concord) and are very familiar with 6.0Ls.