I have a 2009 F-150 with the 4.6 liter. Truck currently has 220,000 miles. I started having a coolant leak that appeared it was coming from between the engine and transmission. Based on this forum and others, it sounded like a sure sign of the intake manifold gasket being bad. Upon inspection, it looked more like the thermostat housing was leaking and coolant was being blown back towards the rear of the engine. And only the driver side of the of the motor was wet with coolant. However, after removing the bolts to the thermostat housing, I noticed the shafts and the threads were extremely rusty and corroded, and they were very difficult to remove. This is making me think that maybe the intake manifold gasket is in fact bad and I should bite the bullet and replace it. Looking for input before digging in further on this one. Thanks in advance.

 

Those manifolds are known to bust right behind the alternator if its the all plastic one. There's also a coolant pipe in the valley below the manifold that's known to leak.

 

That’s exactly what I’m anticipating being the cause. Going to go ahead and tear it down to the intake manifold and start ordering parts.

 

Think I found my leak.

 

Looks like I’ll be replacing the intake itself as well.

 

The replacement should have an aluminum front runner, the part that usually busts on the plastic manifolds. Well the Ford replacement does, couldn't say on aftermarket parts.

 

Currently cleaning/prepping the mounting surfaces. How clean do they need to be and what are the best techniques for prepping these without causing any damage?

 

How clean? Think finely machined surface for best results, you're mating a soft squishy o ring between metal and polymer. There's a little leeway but not much.

This is what we used at the dealer. Works great and won't damage the aluminum decks. 1 disk should be enough, you may want more for other projects in varying grit. You'll also need the quick change adapter to use it with a drill.