Step 2. Remove the bronze frame from the housing and bellows by twisting the frame counterclockwise. The stem is held with a 1/4-20 thread at about 4-5 revolutions. The pressure of the spring will push it off, so anticipate it.
Step 3. Verify the bellows chamber is intact, and free from leaks. First remove the solder seal at the base of the thermostat and empty any remaining alcohol from inside the housing. Suggest using a small plastic measuring cup (Photo 4). 1.5 - 2.0 ounces may come out. Perform a leak down test using a jig of your choosing. In this example a PVC pipe fitting with a rubber seal, and a piece of scrap wood are held using a bar clamp (Photo 5). The PVC end cap is modified with a barb nipple, air hose and a valve to permit small amounts of air to be applied and sealed. A wooden dowel is placed into the threaded base to use as a gauge and a simple red mark is applied (Photo 6). Start by applying small amounts of compressed air (5-10 psi) and monitor the progress of the wood dowel. Fortunately for us, this unit passed the lead down test no further disassembly was required. Unfortunately for our readers, we will not be taking everything apart and won't be able to show you in detail how repairs might be made.
Photo 4 — The soldered seal is removed (or drilled) and any alcohol is drained into a graduated cup. Expect at least one ounce.
Photo 5 — Leak down test jig using PVC Pipe, a wooden dowel, a scrap piece of wood at the top and a bar clamp.
Photo 6 — Close up view of the leak down test wooden dowel. The red mark is the indicator on whether the bellows is not holding pressure.