I have a 2000 F150 with the 5.4L. At around 68k miles I developed a coolant leak in the cylinder head directly under the thermostat. Ford replaced it and made me pay 25% ... fast forward ahead to 110k miles and It has done it again. I have read at least 2 old threads here that indicate the same problem.
The inside of the water jackets had corroded(worn) away until it finally broke through the outside was as a pinhole. the inside of the head was completely corroded out. I havent called ford but this cant be acceptable. This is a definate flaw.
If you have had similar problems ... post here so we can see how many and what ford has done about it .... i will post back here after I call the regeonal office to see what they will do about it!!!

 

I also had a pin hole in my cylinder head of my 4.6. A little jbweld and it has held for about a year and a half and 30,000 miles so far so good, I have 95000 miles on it now.

 

It has not happened yo mine. but I have the 4.6 and an extra grounding strap running from the Negative battery terminal to a bolt on the ehgine front cover. Your situation sounds like electrolysis to me. read the following. http://members.shaw.ca/autocheck/electrolosis.htm
Although this will not fix your current problem it may keep it from reoccuring. The current fix would be to have the hole welded shut.

Regards

Jean Marc Chartier

 

I have a 99 f150 4x4 with a 5 inch lift 33s and flowmasters
I had i pinhole leak also in the head what i did was i driled it and then i taped it so far so good i have 12000k on it

 

I put JBweld on it and it lasted 20k miles .... guess I can only jbweld it again.
Sucks though because i am always worrying about when it is going to start leaking again on a trip. I am amazed that this cant be a commom problems ... what would be the chances I got two defective heads?

 

How often do you flush the coolant? I think it sounds like electrolyses too.....

 

at least once a year

 

Well, that blows my theory........ I do mine on 18 month intervals.....

Mitch

 

Just wanted to refresh this posting. After posting this i talked to ford with no avail. So i JB welded the hole shut. That lasted about 20 thousand miles twice. I am now at 166k and did a better patch job with aluminum bolts and jbweld.

I was just curious how many people have seen this problem?