This melting of the Plastic Manifold near the EGR tube is well known and a very common failure in these GM engines. California no longer allows the Plastic Gasket to be replaced with plastic. Aluminum replacement ONLY! GM has been aware of the problem for years and did nothing. The engine cylinders fill up with coolant and sometimes so much; the engine seizes! Even if the upper intake manifold(s) are replaced; the damage done is irreversible.

Update from Jan 16, 2012: I just replaced the upper intake manifold with plastic replacement kit I ordered online at Rockauto.com. I paid $76. I also ordered 6 new plugs, Bosch +4. I went online for actual videos of replacement process. I did not replace the EGR replacement tube, as I felt the old one was in there too tight and I did not want to create a "new" problem. I drained out all the coolant from the lower intake manifold with a plastic turkey baster. I cleaned it as best I could. I replaced only what came with the kit. It took a while for the car to kick in. White smoke billowed out everywhere. It took about 15 minutes to "flush" out all old remaining coolant from cylinders, etc. The Buick is running now. Engine light is off. I need to smog it and re-register it.

THE CARE RAN FINE ON THE WAY TO WORK 70 MILES AWAY. GOT IN IT AT THE END OF THE DAY AND DROVE IT ABOUT 15 MINUTES INTO MY 1 HR TRIP AND THE THING STARTED LUGGING LIKE IT WAS MISSING SO I DROVE IT A BIT LONGER AND THE HEATER WAS ON AND IT NO LONGER BLEW HEAT AND I COULD SMELL EALLY SWEET SO NO LONGER I GLANCED DOWN, THE TEMP GAUGE WAS RISING THEN II WOULD HERE A GURGGELING SOUND THE GAUGE WOULD GO DOWN THE ABOUT 10 MILES LATER THE SMELL WAS NASTY SO BUY THEN, THE GAUGE WAS PEGGED AND THE IDOIT LIGHT FINALLY CHIMED IN WELL NEEDLESS TO SAY IT GAVE UP THE GHOST AND I FINNALLY HAD TO PULL OVER SO LONG STORY SHORT I HAD IT TOWED TO THE TOWN I HAS IN AND FIXED IT IN 3 HOURS THE INTAKE WAS MELTED AROUND THE EGR STOVE PIPE SO I REPLACED THE LOWER INTAKE GASKET BECAUSE I HAD THE CAR DOWN AND APART.ALL IN ALL I HAD 111 IN THE TOWING BILL. 1 DAY OFF OF WORK TO FIX THE PROBLEM.150 IN THE REPLACEMENT INTAKE (UPPER) 1 GASKET SET AND 10 SMOKE BREAKS WELL ALL OF THIS LASTED 2 WEEKS AND THE ONE SATURDAY I DROVE TO MY BUDDY'S HOUSE TO CAR POOL TO WORK,WE GOT DONE AND ON START UP AFTER WORK THE 3800 SOUNDED LIKE A DURAMAX. THE DEX COOL HAD GOTTEN IN THE MOTOR AND THE BEARING HAD SPUN WELL NEEDLESS TO SAY I HAD TO REPLACE THE CAR WITH ANOTHER PISS POOR DESIGN ON THE GENERALS PART SHAME ON THE GENERAL

Coolant leakage from the plastic upper intake manifold [UIM] and the EGR Stovepipe causing the gasket to fail. This resulted in coolant leaking, with the unattended effort to repair, leaking into the lower intake manifold [LIM], and thus into the oil.

What bothers me most, is that the dealership Santa Monica Auto Group, when they affected a coolant flush and change, did not notice the considerable evidence of coolant leakage.

When checking your oil level, also check the area between the EGR and the intake manifold for any evidence of coolant leakage. I sense that it would should up there first.

Here's what happened, The car started consuming dexcool antifreeze, but none was noticed leaking external to the engine. The upper intake manifold made of plastic apparently warped, and/or a hole burned in near the EGR stove pipe, thus dumping antifreeze into the engine and hydrolocking the engine. Major problem, complete engine failure would not start or run. This car had been well maintained with both regular oil and coolant change's, the car has been adult drivein . Cost to repair $450.00 for just upper intake, add another $450 for the lower intake as well.