2001 F150 5.4L SCREW. History: approx. 140k intake gasket went and I was out of state so had to pay a shop $500. Afterwards wife could always smell coolant. At 166K truck began missing badly so I changed the plugs out. At that time I didn't notice anything wrong with any of the plugs except there was corrosion on COP contacts. I cleaned that off and applied dielectric to the metal. The truck ran great. Now after 1000 miles truck starts running badly again. Decided to change out plugs again and found #4 with at least 1.5 inches of oil or burnt antifreeze in it(in the hole, not the chamber).Also the #4 boot was sloppy on the plug. I put the new plugs and coils on #'s 1~4 and took for test ride. Ran great. It doesn't appear to loose enough fluid to hit the ground (wife is still smelling fluid). Should I just dump in a can of stop leak and pull #4 boot for inspection every 500 miles? Or pull off the intake manifold to try and find the leak. (I am planning on selling the truck either way) Thanks for the help.

 

You most likely have a very small hole in one of the 2 heater hoses that run above that hole. Replace them. Good luck!

 

I'll check it out. Thank you for the reply.

 

Not a chance, they're all good. It's coming from inside the hole. I guess if the head doesn't have any seals involved there it must be a hairline crack in the head.

 

the head gasket is well below the plug well line. The heater hose leak was common. And not as easy to spot as you would think. Most likely would be just a pin hole and wouldnt leak at all times. You would need to run it, make sure it is at operating temps to try and find the leak. Not saying you dont have a crack in the head, but that would be an odd spot for one. Check the cheaper areas with a fine tooth comb before you go and pull the heads. Also, double check the torque on the intake manifold bolts... as specific as they are to torque down, wouldnt surprise me if they have loosened up since it was done recently. There is a water passage/jacket through the head into the intake manifold right behind the number 4 cyl.

 

The isnt another way for water to get there. Replace them.

 

Replace the hoses, if for no other reason than peace of mind, you might be surprised. $500 is cheap for a head gasket job...The heater hoses are even cheaper!

 

Most likely its the intake gasket leaking. Could be porosity in the cyl head casting and during the machining process the porosity cavity was compromised allowing a passage for coolant to migrate into the sparkplug hole. Seen it before but it is usually an infant failure happening during the first 3000 miles of driving. With 140,000 miles a highly doubt this is the problem but just letting you know it is possible. I"m still thinking intake gasket leaking coolant...most likely cause after a coolant hose.