I did the job and replaced upper and lower with genuine GM lower gasket and used the kit from an auto store for the other gaskets (WOW they sure are expensive). I'm getting the same trouble codes as before and have noticed the coolant level going down a little at a time. One day (around 45 degrees) I waited 20-30 minutes after shutting down the truck and the pressure in the coolant system had not subsided. Would that be an indication that there isn't a pressure leak at the manifold gasket? How can I check where the coolant is going (none on ground-must be losing it in the engine)? Is the head gasket a culptrit?

Two places to check if none is on the ground. Check your oil. If it looks a little milky you may have some in there. To see what it would look like, take a little oil and a little coolant, put them in a bottle and shake them up together. This will give you an indication what to look for. Also run a compression check. If coolant is leaking into a cylinder it will show up as higher compression and will blow out moisture after the gage is released. The way I found this out was that I had a set of heads done and the business that did them did not tell me that they had to replace a valve seat. We ran a compression check on all cylinders. Just at 110-120/cylinder except #4. It showed up at 140lb. Released the gage and water vapo blowed out. Pulled the heads again and sure enough it was leaking through a valve seat. Not enough to show any coolant drop but enough to show up on the compression check. After asking the guys the redid the heads....."oh yea, we forgot to mention we redid a valve seat":banghead: :cuss: So I would check either way and more or less depend on a compression check. Because if it is leaking into a cylinder, the water vapor will keep the oil steamed cleaned off of the cylinder walls and then you ARE asking for trouble. If it is leaking into the crankcase it will eventually screw up the bearings then you are looking at a total rebuild. But that's just my $.02 worth. Good luck.

Kevin