Hylomar universal blue failed to seal oil?

[Martin WParticipant @martinw]

I assume that the 2BA thread you are referring to is the cap head bolt at the bottom left in your picture. If this assumption is correct the threaded part of the cap head would not be exposed to any oil in the gearbox. If so then the leak past this cap head might well be due to a failure of the gasket between the flat face of the gearbox and the cover allowing oil to seep through to the unthreaded shank of the 2BA screw and show up as a leak around this cap head bolt. It is relatively simple to confirm if the tapped section is blind or open to the inside of the gearbox. Remove the cap head bolt the fill the gearbox with oil, if it runs out then the threaded section is not blind, if no oil appears then leave it for a few hours or longer and check again and if no oil leaks then it is a fair chance that it is a blind hole.

The Hylomar data sheet states, and I quote: "Hylomar Universal Blue can be used to seal joint faces or threaded parts." While the data sheet specifies surface smoothness limitations for the three grades it does not give any gap filling limitations for threaded parts.

Hope this is of some use to you.

Martin

PS

If the threaded portion of the hole is blind then wrapping the threaded sect with PTFE will not be effective.

Edited By Martin W on 24/06/2020 10:38:45

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Martin W on 24/06/2020 00:39:33:

If it is still of interest the data sheet/instructions for the 3 grades of Hylomar Universal Blue can be found here.

.

Very useful, Martin … Thanks

MichaelG

[J HancockParticipant @jhancock95746]

NEVER ,EVER use the wrong blue Hylomar on a petrol line.

.Unless you like removing blue torpedoes from the line for years to come.

[Martin WParticipant @martinw]

EDIT TO MY PREVIOUS POST

I assume that the 2BA thread you are referring to is the cap head bolt at the bottom left in your picture. If so then I would expect this to screw into a blind hole in the case of the gearbox. If this assumption is correct the threaded part of the cap head would not be exposed to any oil in the gearbox. If so then the leak past this cap head might well be due to a failure of the gasket between the flat face of the gearbox and the cover allowing oil to seep through to the unthreaded shank of the 2BA screw and show up as a leak around this cap head bolt. It is relatively simple to confirm if the tapped section is blind or open to the inside of the gearbox. Remove the cap head bolt the fill the gearbox with oil, if it runs out then the threaded section is not blind, if no oil appears then leave it for a few hours or longer and check again and if no oil leaks then it is a fair chance that it is a blind hole.

The Hylomar data sheet states, and I quote: "Hylomar Universal Blue can be used to seal joint faces or threaded parts." While the data sheet specifies surface smoothness limitations for the three grades it does not give any gap filling limitations for threaded parts.

Hope this is of some use to you.

Martin

PS

If the threaded portion of the hole is blind then wrapping the threaded sect with PTFE will not be effective.

Edited By Martin W on 24/06/2020 10:38:45

Should have included the sentence highlighted in italics.

OOPS Bad day at the office

[Martin WParticipant @martinw]

A quick and dirty way that may fix the leak is to fit either a copper or fibre washer under the head of the bolt having coated all parts with Hylomar and assemble while still wet. If this doesn't work clean up parts and try assembly dry. The advantage is that you already have the Hylomar and if neither option works all you have lost is the cost of a small washer.

Martin

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