Hi guys, new here. I have a 98 f-150 SC 4x4 4.6 romeo. It just started missing about a mile from home and cel was flashing. I checked the codes, misfire cyl 6+7. When pulled the plugs, there was anti freeze in the plug holes and halfway up the boot. I since pulled the intake and I'm hoping I found the problem.The 2 long bolts around the thermostat were wet with it looks like anti freeze and oil. Do these bolts need sealant on the threads when installing, and is this a common problem with these motors? This is my first modular motor, and its been an education so far. Thanks for any help you can give me!

 

did you check if it wasnt a heater hose leaking?

 

yes, It looks like it could be the intake gasket. But I'm not sure yet. Yesterday, I tried to do a leakdown test to check the head gasket, a waste of time. The intake valve on #6 cyl wouldn't seat, so air just kept leaking out of it. I decided to pull the heads and replace the head gaskets, and do a valve job.

 

Intake manifold gasket or the thermostat housing like you said. Head gasket is below the plug well, therefor cannot leak into the plug well itself. Heater hoses would not leak on that side. 6 and 7 are on the drivers side, second and 3rd back.

 

What do you think about the intake valve not seating? I've read that the valve seats on these heads sometimes move out of their bore. That makes sense if it was overheated, but it wasn't.The temp gauge was at normal. My buddy is tryin to talk me into buyin a used head, get the motor back together, and get rid of it. What do you think? Thanx