1999 Olds 88 water in oil pan, runs rough - any simple fix?

My 1999 Olds 88 was running fine then the temp starting going up yesterday but never reached the red zone. I stopped the car, put in some water and checked the oil level and all seemed to be ok. But then I noticed that after I got home and checked the water level again - more water was needed. After putting in a couple gallons of water, I checked the oil dipstick and saw that the oil level had gone up an inch or so!

It also is running rough but I do not notice any pressure when removing the radiator cap - which I have been told is a sign of a blown head gasket. The water level stays level until the engine is running at which time you can watch the water level drop as long as the engine is on.

I would like to fix the problem without having to rebuild the entire engine but do not know if that is possible at this point. I was just cleaning the car up to sell it and that is why I don't want to dump too much money into it.

The car has 95k miles and someone told me that the plastic intake manifold might be the cause of this problem - HELP - I have no idea what could be the problem which is why I am posting this thread.

Yeah, it is the plastic upper intake plenum. Go to napa and buy it, because the orginal wasn't reinforced and the new one is. The orginal had a design flaw and it warps at the intake side and antifreeze starts leaking, if it lasted 95k you did pretty good on the orginal. You better fix that a.s.a.p because you don't want antifreeze going into your oil it will f***up your engine. Change oil too, put orginal dex cool antifreeze in and to boot you should run some rislone through also to clean the engine. The job isn't too hard, if you got a couple of hours.

I would first do a pressure test to be sure what is wrong,if you go ahead and do the intake manifold and there is a head gasket gone you will have done the job for nothing,have it tested to be sure.

I wouldn't put dexcool back in though... Flush the coolant system and then replace the Dexcool with the regular green coolant.

I wouldn't put dexcool back in though... Flush the coolant system and then replace the Dexcool with the regular green coolant.
Ok if they can be sure all the red is out, an intermix can cause problems.

Wasn't there a lengthy thread on dexcool vs green stuff not too long ago? lemme see if I can find it...

wow...I did a search and came up with several threads about dexcool...

http://www.automotiveforums.com/vbulletin/search.php?searchid=1509552

Yeah, but their is nothing wrong with dexcool, I think you should use what came with the car orginally. I also know prestone makes green antifreeze that can mix with any color, so I guess it dosen't make a difference.