'99 3.8 Intake Manifold: Second Repair.

[12Ounce]

BACKGROUND: A few years back, when my '99 had approx 60k mi, the DPFE sensor had to be replaced. At 90k mi, the infamous P0171 & P0174 also showed up. The conventional wisdom of the day was "replace all gaskets and seals on upper and lower intake manifolds, and replace the LH valve cover".
CONDITIONS FOUND: There was a little fresh oil on top of the "spacer". The lower intake manifold, including the IMRC butterflies, was a gooey mess. Was this condition worsened by the earlier EGR problem? Very difficult to clean. The EGR jets were all fouled ... a couple were completely plugged.
ACTIONS TAKEN: Cleaning done and recommended replacements/repairs made. NOTE: The improved "green" isolator bolts were not then available. Taking note of how the "upper" was actually a loosely assembled clipped together two-piece part, I decided to use some sensor-safe RTV to better support the inside piece. In fact, the "upper" inside part was RTV'd to the "spacer" .. around the six air horn connectors. This experiment may have had an unintended/unexpected good impact.

CURRENTLY: The '99 now has 160k miles and is beginning to pre-knock under load. No codes yet. I decide to do the intake manifold repairs again with the new green isolator bolts, and also replace the long overdue plugs and serpertine belt.
CONDITIONS FOUND: Much more oil found on the "spacer" ... perhaps a few ounces. However, the "lower" was surprisingly clean. No goo. The IMRC butterflys almost as clean as when I earlier left them. Almost NOTHING in the EGR jets ... not enough to dirty a pipe cleaner. Apparently the applied RTV successfully sealed the "spacer" away from the "lower", preventing the oil from leaking down onto the intake manifold runners and causing the gooey residue. ???
ACTIONS TAKEN: All ribbed o-rings and isolator bolts replaced. All bolts torqued (10Nm) in two-step sequence per Haynes manual. All old RTV peeled away from the six air horn connections and connections re-RTV'd. Don't know for sure if the RTV was important, but why take chances. (I wish I knew how to insert a digital image here. ???). New double-platinum plugs and belt. Winney runs great again! The plugs were probably causing the pre-knock, but I'm glad to get rid of old black isolator bolts ... though I didn't see any seal loss... they would have eventually caused a problem.

TIP OF THE DAY: Do not leave Haynes manual outside overnight if rain is expected.

[DRW1000]

I know it's just me but I don't understand where you put the RTV..

Since you still had a lot of oil in the intake after replacing the valve cover It would seem that the redesigned valve cover did little good except increase the profits at FORD.

[12Ounce]

Yeah, like I say ... I wish I knew how to insert a photo in these postings.

The "upper" sits atop the "spacer" ... and six, some what rectangular, "upper" air horn spouts fit inside six "spacer" receivers ... male to female loose slip fit ... its not a very tight fit, certainly not liquid tight. That's where the RTV goes ... to make these six connections liquid tight.

I think the new valve cover may be improved. In fact, I did not mention that the PCV valve is clean and nearly dry. And what I can see inside the valve cover PCV hole is spotless...So I believe there now may be less oil sent into the intake manifold, but now ALL of it is now getting captured atop the spacer ... none goes downstairs onto the IMRC area like before ... due to the RTV'd connections.

Just my theory.