I too have a 1998 Pontiac Transport and just had to have the intake manifold gasket replaced due to its failure. This vehicle has 115,000 miles and runs strong. I also have a 1998 Chevrolet Silverado and had to replace the intake manifold gasket on it. Several other people I know have had similar problems. I wonder if it doesn't have something to due with the type of coolant they are using. Have owned other GM products that used the old style coolant and never had any of these types of problems. Any thoughts?
Coolant could be the answer. Extended life has lower pH, green is more like acid. I had the tranny fixed 2 times and blown head gasket. Now main shaft bearing turned (garbage engine) Bad car!
I realize this comment is coming on about four years after your post, but as I too have a 1998 Trans Sport Montana, I can tell you, from educating myself from these posts, that the problem with the coolant leaking into the oil results from the coolant Dex-cool, which should be changed far more often than what the owner's manual indicates.
My Pontiac's temperature gauge constantly goes into the red and beyond now, and no heat comes from the heater, and I expect it to blow any day. A fitting end for a delightful van with a multitude of problems!
Today, Mar 5, 2009, My Transport just jumped timing. Six months ago we replaced the head and new intake gaskets etc, two years ago it was the water pump, intake gasket, & transmission. Now this, so now I am to the point where I have more invested in it than it is worth!
I also have a 98 Pontiac Transport. To this day my husband hates this vehicle. It has been a pain from every angle. In Jan 2008 I had the intake manifold gasket replaced. And now in July of 2009 I am being told that air is leaking in the engine causing it to overheat. What a joke, I would not recommend fixing a Transport at all. Replace it and find something worthwhile to drive.
Apparently there are service bulletins out from GM that warn of intake manifold and head gasket failures. There are new gaskets out that compensate for the issues.
I too had the problem of "air getting into the system" and was told it just needs to work out.. be bled.. etc.. What the wonderful mechanics didn't know is that the air comes from head gasket failure.. typically on cylinders 3 and 6. Just refilling the coolant will result in engine failure, over heating and severe damage to the aluminum heads and bearings.
Trade it in for something better, or be willing to pay a couple of grand for them to be fixed.
I realize some of you have had problems, but I haven't had any of your problems. The Trans Sport is excellent in the snow. It runs great. I bought it with 80,000 miles, and it currently has 160,000 miles. I would not trade it for the world. I've had Buick Centuries, a Honda Civic and two Neons. Those cars were in need of serious repairs before they hit 80,000. The worst I've had to repair was called maintenance by the mechanic. As long as you maintain the car, you will have a happy and cheap life with the car. I've spent many times more on gas than the purchase price and repairs put together.
My step daughter's Trans Sport broke down in the middle of an intersection. We tried restarting it; it would only sputter and stall. I changed the fuel filter, checked fuel pressure and checked spark plugs; there plenty of spark. Now I suspect it's the timing chain, and your comment about jumping the timing chain reiterates my suspicion. I am not looking forward to this...