before going to crazy with chemical tests, borrow or rent a cooling system tester.
pressurize the system to 18 pound, check it in 45 minutes and the pressure will be down.

then re-pressurize the system and go back and wiggle and pull on every hoses, not to mention the obvious TBH leaks, expansion tanks leaks there are at least a dozen and a half hose clamps that could be leaking.

 

Another spot to check is the bell housing.
I had a coolant leak on the rear of the head. It would drip onto and run down the bell housing (pass side) then drip onto the the hot cat. The coolant would evaporate before it had a chance to drip onto the ground.

 

sneaky!!!

 

Parked on pavement and there was nothing. Nothing obvious from underneath either. I bought some uv dye and need to find a coolant system tester at some point today. I think the bottom line is I have a blown hg.

 

just because you don't have water on the ground does not mean that you don't have an external leak. But hey if you think its head gasket go for it.

 

I definitely would not change the HG without proof they are blown.

 

I'm guessing it was an air pocket. If we are talking a 1/2 gallon of coolant disappearing over the weekend its going to be a pretty good leak. You would notice the puddle from that, and if it got into the cylinder I doubt it would run.

How did you bleed your cooling system last? I've found I get a lot more air out when I lift the front end a good amount..or drive up on a snowbank like I did last time.

Edit: I also use a 03-04 style upper radiator hose with the bleed screw at the joint.

 

You need to bleed the system a few times to eliminate the air pocket idea.

I had the same systems a long time ago and it ended up being an external HG leak. Had to do about 15 mins of pressurizing the system to get it to show up. You won't always get a puddle if it's burning off on some part of the exhaust.

But if it is external that is the best one to have. Just be happy it's not an internal leak.