Update: I developed an air leak in the tractor on Saturday. Any air leak is usually sufficient cause to shut the truck down. Risks, however, are taken. My air leak was serious enough, but only leaked when I stepped on the brakes. Not serious enough to cause the air valves to pop. I was running about 80-90 psi most of the time, not the usual or proper 120-125 psi. PSI dropped to 60 when the brakes were engaged, which is dangerous territory. So I proceeded on to Calgary and made delivery. Consulting with my shop foreman, who cautioned me on such risk-taking, I returned to Great Falls, MT. A Mack Truck service center was found, problem discovered, parts to be ordered. Diagnosis: two brake chambers. I, however, am stuck in GF and am headed to the hotel until the repairs are complete… probably tomorrow or Wednesday. Next shave likely tomorrow morning from the Comfort Inns and Suites.