while replacing the upper plenum . . . (1998 GP GT)

[worb4me]

Does it make the most sense to just go and do the lim gasket also? Nobody really wants to go in their twice if they want trouble free miles out of the car. Of course you could use that logic to say do the head gaskets also, but the 3800 has iron heads and *rarely* needs hg's replaced. Or so they say.

 

 I'm assuming the plastic plenum is going to need replacing w/almost 128k on the car. There are leakage issues, haven't put much effort spotting exactly where the oil and coolant is leaking from as of yet. But for 78$ what's the big deal.

 

I'm assuming that the lim gaskets are crap as in many other engines of this era. I _will_ have to do the valve cover gaskets, I can already tell that's one of the problems, so therefore should I just go whole hog, buy a complete gaskets set (w/the not needed head set included), being the vc set is 40 bucks, and the "complete" set is 125$, or less w/discounts?

 

 Now once I actually finish the wheel bearing and that damned coolant elbow, I will drive it, get it heated up, and see what's the exact problem/s. I'm just trying to plan for the inevitable knowing the way these issues come up.

 

is  the Felpro HS9917 PT-3 the best set available? Head gaskets need to be steel, I guess it were nice if the LIM gaskets were too. If there is a better set (or individual gaskets) please advise.

[Psych0matt]

If you're going to be in there and think it might need it eventually anyway, might as well do it while you're there. I had to do the lower intake on my 92 shortly after I bought it because it was leaking, and that's most of the reason why I haven't done my intake swap, simply because I don't want to terret down again after already having fixed it.

[Imp558]

They aren't something that the L36 is really known for, I mean they do go bad but it's not like as common as the UIM cracking. But realistically they can be had for $15. from Rockauto so it makes sense to replace while you're in there. The spark plugs would likely need replaced if you had a UIM crack and fill cylinders with water but that's not the case with yours. No amount of cleaning worked on mine so I guessed it was something to do with the ceramic being saturated with coolant.

 

I've had oil leaking from the oil pan gasket, both front and rear seals and valve covers, just have to get in there with a pressure washer and clean really good so you can watch it. Dollar Store "Scrubbing Bubbles" type bathroom cleaner makes really good engine cleaner for that, let it sit all over everything for about 10 minutes before rinsing.

[jman093]

I don't bother with the LIM. I have done dozens of upper intakes, but never in my life done a LIM on an L36. If it's actually leaking....sure, but they just don't leak that often. In the last couple years, I have just started plugging the damn coolant passages in the LIM. It's all just such a terrible design. Even if you use one of the revised upper intake manifold kits, it will start leaking again someday just like the original. The throttle body heater passages aren't needed whatsoever, so they get plugged and fixed for good. Cooler intake air temps anyways.

[digitaloutsider]

The LIMs need to be done if they are factory.. they are junk.  There's a reason why GM made a revised set....

[White93z34]

Yeah, GM didn't redesign the gaskets some 3 times for no reason. May as well do Lower intake and valve cover gaskets in addition to the upper plenum. Do it once and never worry about it again.