98 Lumina intake or head Gasket

I have a 98 lumina 3.1 I replaced the themostat and water pump. Everything was woking fine with heater working. today I cant get no heat and is running a little high on temp until the thermo kicks in. I noticed what could be coolant with the oil not alot but I can see notice it. Now what gasket could of went south. intake or head. or both. Kinda of sucks because everything was working fine yesterday just like it should. Have a Save new year.

if your lower intake gasket went out, air (when engine is cooling) and oil could enter the coolant and the air reacts with dexcool to create sludge which then could clog your heater core. are you still running dexcool and do you see any sludge in your coolant reservoir?

see http://www.steelseal.com , or blue devil.

Well I plan on starting the intake gasket next week. The heater blows plenty of hot air when I have the coolant level where it needs to be. I for sure have a coolant leak that is going on. car runs fine other than the coolant leak. Milky and and way to much mixture when I check the oil dip stick. My only question is how can you tell if its a LMG or head gasket that is bad. Gary

Well I plan on starting the intake gasket next week. The heater blows plenty of hot air when I have the coolant level where it needs to be. I for sure have a coolant leak that is going on. car runs fine other than the coolant leak. Milky and and way to much mixture when I check the oil dip stick. My only question is how can you tell if its a LMG or head gasket that is bad. Gary
i had the same thing hapen on my 96 the intake gasket is made of hard plastic it was cracked and the more i ran it the more water got in the oil i thought it was the head gasket till i took it down replaced intake gasket that was craked in the conner and it runs fine

If i were u, I'd pull the lower intake manifold and check the gasket. You should be able to see if it has deteriozed enough to leak instead of just a tore up gasket from the removal of the lim. IF the gasket's look good then go for the head gasket's and check the head's for warpage. If warped, get them resurfaced. That's what i would do. C-ya Scott

definitely get the steel LIM gasket, felpro sells both plastic and steel but i'd avoid plastic again... along with dexcool - just doesn't do too well when you get air in the coolant passages

i forget which, i think the instructions with felpro head bolts (or maybe headgasket), they tell you to follow their instructions, not OEM factory manual instructions... something like 80ft/lb + 90 degrees

have someone mark off a diagram of the head bolts so you dont miss a 80ft/lb torque or miss a 90 degree turn, i forgot at one point where i was, so threw out a head gasket and set of bolts :(

Just completed mine, 90% probability it's the LIM gasket. I've read on one of the forums that you can check for head gasket by checking the sparks, if the spark head is not milky, it's not the heads. Here are some links I found, they will be useful to you:
http://hubpages.com/hub/Chevy-31-Liter-Engine-Leaking-Intake-Manifold-Gasket-and-Warped-Heads
http://www.garagejournal.com/forum/showthread.php?t=60677&showall=1
http://www.autoforumz.com/99-Lumina-Intake-gasket-replacement-procedures-ftopict229025.html
http://www.freeautoanswers.com/intakemanifold.html
http://www.garagejournal.com/forum/showthread.php?t=39862
http://www.zrxoa.org/forums/showthread.php?t=245429
http://www.w-body.com/showthread.php/8442-O-Ring-(Oil-Pump-Drive-Seal)-Fix-(Pictures)/page3