Hi Joe, are you certain that your manifold is the problem and is not sealing? Have the cylinder heads been taken off the car?
Ok, if the heads were not removed prior to this problem I would suspect that possibly either the wrong intake manifold gaskets were used or they were put on backwards. There are a couple of different gaskets available. If the heads were removed and resurfaced then you may have a problem with the mating surfaces lining up. Either way it looks like it will have to come apart again. Let me know what you find.
We purchased the gaskets from mercedes. We put the side with the red sealant that comes on the gasket down towards the cylinder head just like the mercedes service manager told us to do. There was actually a picture on the gasket package to show which way to put them on. I just can't figure what could be leaking. I don't know what removing them again is going to do until I know where The leak is coming from
When you originally removed the intake did you drain the coolant? Is it possible that coolant ran ino the cylinders and simply needs to burn off or have you given it enough time for that to happen already? If you're burning coolant you should be able to look at the plugs and see which cylinder it is or look at the top of the pistons. I'd also expect a misfire. You shouldn't need sealant on the gaskets. Just inspect your surfaces really well. It shouldn't matter much hot or cold when you pressurize the system. Let me know what you find.
A coolant leak from the intake manifold into an intake port would not necessarily build up pressure in the cooling system. I would take the car for a good test drive and watch the temperature and see if the smoking diminishes before you get too deep into it. It can take awhile to burn coolant out of the exhaust system. Keep me posted.