Hi everyone,
I need some help here... its a long story but aren't they all?

Truck is a 2003 Expedition with the 5.4L
Truck started idling rough every now and then but would smooth out after a while, then it would come back at stoplights sometimes... figured it was a cop but it never threw a code. Finally threw a code, showed a cylinder 4 misfire. Didn't have my multimeter to test it so i just switched the cops from cylinder 1 and 4. Code went away, never came back. Still had issue of running rough.

2 months later were driving from Phoenix to Flagstaff, got a low oil/high temp light. pulled over and it was low on coolant (we never saw or suspected a leak). Poured in 1 gallon of the correct motorcraft coolant. (mixed it 50/50).Truck was fine after that, drove home. Got home after the two hour drive, we let it cool down and poured another 1/2 gal of coolant in it.

I was worried about where the heck the coolant went but didn't worry too much since the truck was fine.

A week later, wife called and said heater didn't work (well it did but it was erratic and the temperature started jumping around. I replaced the t-stat just in case and figured I would do a coolant flush. I figured the heater core and/or radiator was plugged . Got some flush, drained radiator, put two bottles of flush in, filled rest with water... drove it around watching the temperature carefully... and it did GREAT... temp went up once and then settled in very nicely AND the heater worked just fine.

Got back home and was going to drain it and finish the flush when it started idling badly again but much worse... felt like cylinder wasn't firing but there was NO CODE. Was late so I didn't do much more... woke up had to get some milk... on the way to the store I noticed there was a lot of white smoke coming from the tailpipe... damn... I immediately figured blown head gasket.

So...
This is where it is at... it probably got hot but as soon as the light came one, we drove maybe one more mile and then shut it down... to me that doesn't seem long enough to blow a heat gasket (especially these 5.4L ones).
There is the white milky substance under the oil cap (but none on the dipstick).
I haven't done anything else or checked anything else out because I am not excited to tackle it right now.

I have replaced head gaskets on honda 4cyl,chevy 350's but never one of these... I know I can do it but I know that it is going to be a PITA.

Can it be anything else? Intake coolant leak? Any ideas or suggestions if I dive into it soon?

Thanks in advance.

 

If it was an intake coolant leak, it would probably be external. You need to do a pressure test on the cooling system to find the leak. Sounds like a head gasket to me.