WELL thanks everyone for your advice, but this story does not have a happy ending. While tracking down the source of the oil leak, I found a fairly large hole punched in the valve cover from inside the engine. My buddy took a look and found cylinder 2 has no compression, all the other cylinders are fine. The hole is right next to cylinder number 2, so obviously something catastrophic has happened.

I'll be pulling the valve cover off later this week to see what, precisely has happened. I'm not entirely sure what worst-case is for this, I imagine a crate motor is a few thousand bucks. Maybe a rocker arm just slipped off a stud or something, I'm not entirely sure how it looks under there.

 

A common problem is that cylinder #2 drops a valve seat, it is almost always #2. Then the cam follower falls out.

How many miles? Did it ever overheat?

Keep us posted.

 

It has run hot enough to sound the temperature alert chime once that I know of. It does lose some coolant at the thermostat cover, I can't figure out what's up with that, replaced it three times already.

How bad is "dropping a valve seat" and all that?

 

It depends...

You'll be pulling the head. The valve seat may have cracked allowing it to come out but any overheat can do it as well.

There might be some piston damage but it may not be enough to worry about.

Replace the seat and the valve if necessary. Replace the cam follower, hopefully the cam is OK.

Take some pics if you can.

 

Doesn't it always...

Here's the hole in the valve cover. I don't have much else to offer at the moment. I'll be removing the valve cover this evening or tomorrow evening, as time permits.

 

You might get lucky and it's just the follower.

 

Yeah, I'm actually not TOO worried. Even though we're expecting some downtime with the truck at this point, she's still got something to drive to work and back. I've never pulled a head, but I love working on cars, so I'm honestly looking forwards to it just a little bit.

My mechanic friend thinks it's the rocker arm, so we'll see.

 

If the rocker arm had popped out, shouldn't I still have compression? There's no compression in that cylinder.

 

Well, too bad it wasn't an easy fix but sounds like you'll have fun wrenching on it.

I assume you mean the radiator cap above? The thermostat sits underneath on the 4.7L. If you've replaced the cap and it still leaks at the neck, there may be a crack or wear, preventing a seal. JB weld can sometimes get you by but a replacement may be in order.

Edit... just remembered that the upper radiator hose is where the "neck" is located and not on the actual radiator. Not near my truck to see right now, but maybe you can just replace the T-junction/filler neck?

 

it leaks around the thermostat housing on the bottom passenger side of the engine. No idea why, the surface is perfectly flat, clean, and new housing and thermostat always leaks. I must be doing something horribly wrong. Maybe over-tightening it.