Re: water pressure guage?
OK -- enough already. Air is not "bled out of the system". Just like the speedometer, water pressure, wherever you tap into the system, compresses air in the tube feeding the gauge. There is no escape for this air. If there was, water would come out and your feet would get wet. The air trapped and compressed in the tube causes the Bourdon tube in the gauge to unwind moving the dial. There is no water or air flow in the system. Only slight compression of air due to the water pressure.
As for where to tap into the engine, it varies by engine and cooling system design. On some the tell tale works just fine. In the grand scheme of things the telltale is just a pinhole leak in the cooling system compared to the wide open flow of cooling water through the exhaust. On other engines, you do need to tap into the water jacket or some other spot where pressures is greatest. The simplest way to test this is to "T" into the telltale. If it works great. If not, find a new spot.
