GM-GMC: White smoke all the time and coolant loss, cylinder head gaskets, coolant loss

Question
How would I check to see if its either one or would a mechanic absolutely have to do it? Facing the engine the right side block has blue sealent that looks fresh(less than 6 months maybe) under the head or along side the gap where the head meets block. AS IS STATE What now and around how much?-------------------------
Followup To
Question -
Hello I have just in the past three weeks purchased from a local dealer a 1988 GMC Sierra 1500. 350 V8 5.7L. I have white smoke on start up and the whole time it runs. Have to keep checking coolant and adding a little every other day. Smells like oil burning but someone told me it could be antifreeze leaking into the heads. What do you think and what should I do? D.S.
Answer -
Adding coolant is not normal.  The white smoke confirms that you have coolant getting into the cylinders due to a bad head gasket (or maybe both head gaskets) and/or warped or cracked cylinder heads.

Your truck was very likely overheated by the previous owner and then traded when the coolant consumption began.  I would complain to the dealership where you purchased it.  You should have some type of purchase warranty unless your state permits vehicles to be sold "as is."

Answer
The blue sealant may be under the top cover, called a rocker arm cover.  It is used there to prevent oil leaks from the raocer arms on top of the valves.

If the sealant is actually between the block and cylinder head (near where the spark plugs go in) there is a serious problem with the head or block being flat and level.  No sealant is supposed to be used on cylinder head gaskets.

A mechanic will have to perform the tests becuase it requires specialized equipment.  Repair costs would likely be several hundred dollars.

You may wish to try a product called "Bar's Leaks" for radiator and cooling system leaks.  This product, made of ginger root and crushed walnut shells, was specified for Cadillacs when the first front wheel drive versions appeared in the mid-1980s.  I have used it to seal coolant leaks on diesel engine cylinder head studs.  If it works for you, it could save you a lot of money.