2002 XLT 4.6L misfires and leaking coolant

[vhfreak]

I've got an early build (08/01) 2002 Limited with the 4.6L V8 engine. I changed all the plugs about a month ago or so, and a week or so later, got a misfire code on cylinder #8 . Checked the coil and the plug, both of which were fine, but the boot was pretty nasty, so I cleaned it up and reinstalled, and it behaved pretty well for a couple of weeks.

In the meantime I've been trying to figure out why the boot was so nasty looking, and I'm thinking it's getting coolant in there, which would definitely cause a misfire, and from what I read, this model year likes to develop a leak in the neighborhood of the intake manifold to help facilitate that. That would also explain me occasionally smelling coolant of late.

I did fill the coolant reservoir up to the fill line about two weeks ago just to have a baseline, and checked it again today, and it had clearly lost a couple inches worth of coolant. So yaaaay.

I've read a bit about it, and it seems this is probably either (a) the manifold is cracked and leaking, (b) the manifold gasket is leaking, or (c) the thermostat is leaking.

My questions are as follows:

1. Is there a good way to determine whether it's (a), (b), or (c) prior to pulling the manifold? I would hate to buy a manifold and tear it down to find out it was the gasket. I'd also hate to tear it down to replace the gasket and find out it was the manifold, and I don't have one handy. There's so much junk riding above the manifold anyway, that it's not even terribly clear where the leak is coming from. Any advice on doing a proper diagnosis?

2. How can I tell if my truck has the crappy plastic manifold? I can see aluminum running across the front, but I'm not sure if that's indicative of anything or not.

3. If it turns out to be the blasted manifold, do we feel pretty good about the Dorman replacement? We're in the 130K range, and I really don't want to drop $$$ on an OEM if the Dorman is generally accepted to be a good replacement. I've seen a few random individuals who are vocal about it not being as good, but then most of the reviews on it are pretty good at the same time.

Any advice anyone could give would be appreciated. I'm far from a mechanic, but I'm pretty good at following directions when it comes to replacing stuff like this. I just don't trust myself when it comes to the diagnosis.

Thanks!

 

[vhfreak]

This morning before heading to work, I refilled the coolant overflow container back up to the fill line and then when I got to work (a ten minute ride away), popped the hood and took a good look.

I could definitely see coolant around the thermostat area and working its way back in the neighborhood of the #5- #8 plugs, though it did not appear to be leaking from the top of the manifold where the thermostat attaches. I could see it at the bottom of the aluminum part the thermostat is bolted to.

Also, was able to see the OEM part # of the manifold itself, which was 1L2E-9424-FA. Don't know if that helps tell if it's one of the bad manifold parts or the less bad manifold parts.

 

[lincolnshibuya]

the intake manifold coolant leak is a known issue, in my case I could see coolant going down in the engine valley and eventually leaving marks near the bellhousing at the rear of the engine. I've replaced mine with Dorman and still going strong. At 140k miles my COPs started to misfire (3 out of 8) and I recently replaced all of them before they kill my cats.

all gen3 explorers has plastic intake manifold, my 98 lincoln continental has metal version of it.

https://www.facebook.com/media/set/?set=a.360434580691366.78120.110528882348605&type=3

 

[rocco123]

Dorman replacement on a 4.6 works fine. don't let Dormans info fool you. The plastic channel where gasket / sealing ring sits gets all crumbled.