One of the most common parts missing on used engines is the sight glass tube, probably because they are easily broken if
precautions are not taken to protect them. Replacing the tube is actually quite simple.
How To Change a Sight Glass Tube
Step 1: Determine the length of tube required.
Step 2: Prepare tube for insertion.
Step 3: Insert the tube.
If you are using a 1" long tube locate the gaskets even with the ends of the tube, place the tube between the ends and snug up the jam nuts, do not over tighten.
If you are using a 1 1/8" long tube slide the bottom gasket about 1/4" from end of tube, locate the top gasket 1/16 of an inch from the end. Drop the tube into the bottom fitting and raise it until the top gasket meets the fitting, snug the top jam nut. Holding the tube carefully slide jam nut and gasket down and snug up jam nut, do not over tighten.
Replacing a Sight Glass Unit
When installing the unit it is advised to use a product such as Loctite 565 to seal the threads.
Thread bottom elbow into bushing on boiler so that port is facing up. Prepare sight glass tube as per instruction at top of page, insert tube into port and let it drop down far enough to be able to thread top elbow into bushing so port faces down. Center the tube and snug up jam nuts, do not over tighten.