How can I seal this oil sight glass?

[choochoo_balooParticipant @choochoo_baloo]

As I slowly win the battle to seal all leaks on my Senior M1, I've now spotted a slow leak on the bottom of the power feed gearbox sight glass.

• I assume the knurled chrome ring holds the glass?
• That brass tube is a press fit into the cast iron bore?
• Why does the brass tube have the diamterriclaly opposite notches on teh inside edge?

In which case will a small wipe of Hylomar sealant around chrome ring thread, first left separated to evaporate, do the trick? Any other suggestions please?

Thanks in advance.

NB The greased Flexoid gasket I made to replace the dry cork, seems to hold well.

[choochoo_balooParticipant @choochoo_baloo]

[not done it yetParticipant @notdoneityet]

The brass ring has diametrically opposite slots/notches for a reason. They are for a wide screwdriver?  That might answer your second question?

What it needs, to stop the leak, rather depends on where the oil is leaking from.

Edited By not done it yet on 31/05/2020 14:22:07

[choochoo_balooParticipant @choochoo_baloo]

Posted by not done it yet on 31/05/2020 14:21:24:

What it needs, to stop the leak, rather depends on where the oil is leaking from.

Edited By not done it yet on 31/05/2020 14:22:07

I forgot to mention: there was a obvious oil fill along bottom glass/chrome ring interface – suggests this joint is leaking, running along oustide and then down main gearbox.

So how do I get at it without cracking the glass disc?

Edited By choochoo_baloo on 31/05/2020 14:31:54

[KWILParticipant @kwil]

It would appear that the sight glass assembly is in two main parts, the chrome ring complete with glass and the brass fitting that merely pulls the fitting into/onto the outer face.

Remove the brass ring and the whole may come away. Clean, seal to outer face and retighten the retaining brass ring?

Do not have Senior mill, but that is what it looks like to me.

[Howard LewisParticipant @howardlewis46836]

If all else fails, is there enough thread engagement to allow placing a thin,(say 1.5 mm section ) 'O' ring between the glass and the main casting tom provide a seal?

Or does the Chrome plated ring screw onto the brass sleeve?

Howard

[mechman48Participant @mechman48]

Howard beat me to it, how about a small section 'O' ring that fits in the chrome ring to seal the glass junction of the brass body at the end of the thread, if you get my drift.

George.

[IgnatzParticipant @ignatz]

If all else fails, another option would be to reassemble the sight glass assembly using one of the "Form-A-Gasket" formulas offered by Permatex. These mixtures will fill and form a flexible gasketing that is oil and temperature resistant… and best of all, will come away easily if future disassembly is required.

Permatex products

[Kiwi BlokeParticipant @kiwibloke62605]

I think you'll find that the brass piece is externally threaded, and screws into the CI body of the gearbox. The 'slots' are there for a driver ( best made, with a pilot to fit the bore ). The chromed ring probably therefore screws onto an extension of the threads, trapping the glass between the two. Be careful when attacking the chromed part – it's likely to be brass, so easily marred.

Hylomar is a good sealant, if subsequent disassembly is required, but pretty much any low-strength oil-resisting sealant will do here. Loctite 567 Hydraulic Sealant (assuming the number is current) is a great sealant for drain plugs and any union which relies on the threads for sealing. It sets, but is easy to undo. I wouldn't use it on the chromed ring, however – that needs to be easily undone.

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