GM-GMC: Coolant loss, head gasket leak, coolant loss

Question
I have a 1985 Chev Van C20.  I was getting water in the oil pan so I got some Barsleak and followed directions.  I no longer get water in the oil but I still lose coolant.  I cannot find a leak visually.  Sometimes it appears the exhaust is white like coolant is burning and has that overheating smell.  It runs a little rough and I cannot seem to smooth it out so I am thinking I have either a intake leak or possible possible cracked head/gasket leak.  It runs fine down the road with no problem.  The white exhaust is only on occasion like coolant has pooled up somewhere then burns.  Any ideas?  I appreciate your help as I am looking for anything short of pulling a head.  Thanks.

Answer
I think that you will wind up pulling one or both cylinder heads and, as a van owner myself, I know how bad that will be.

You did not specify your engine, but the GM 6.2 diesel is known to crack heads and suffer coolant loss as a result.

If you have a gas engine, you might pull the spark plugs and look for signs of rust.  Or, you might try disconnecting each spark plug wire, in turn, when the engine is running rough, to determine which cylinder is affected.

All engines are subject to this kind of problem if they overheat.  The only prevention is to make sure that they are never allowed to do so.  Cooling system maintenance and repair is essential to prevent costly damage.