Crankcase/gearbox gasket: hermetite or what?

[mogmog2]

Will be reassembling my MS gearbox onto the MD2B tomorrow. This joint holds the engine oil in, it would seem (IE it's in the bilge now...).

I have bought some flexoid gasket paper for this.

I have read around on good practice. Many on here espouse the use of grease, some hermetite and some nothing. In the olden days I used hermetite or hylomar because that's what my father did but I can't remember any rules on this.

Unsurprisingly after 30+ years, my hermetite went hard and I threw it out not that long ago. So, should I use grease, nothing or hermetite (or equivalent)?
Many thanks.

 

[PaulRainbow]

I would use grease on both sides.

 

[VicS]

There is no suggestion in the workshop manual that any gasket cement should be used http://www.boatinfo.no/lib/volvo/manuals/ms-msb.html#/0

Personally I'd probably apply a very light coating of grease, but that could be wrong!

 

[elton]

I'd use Silicone RTV, as I've always used on motorcycle engines and gearboxes.

 

[PaulRainbow]

I'd use Silicone RTV, as I've always used on motorcycle engines and gearboxes.

Why use instant gasket, on a gasket

 

[Heckler]

Why use instant gasket, on a gasket

Indeed, but when I was rebuilding Rolls Royce diesels the factory recommendation was to use Hylomar NOT that horrible instant gasket sh, one of their products, on one side of the gasket. However, If the faces of the joint are good then grease on both sides is good.
Stu

 

[pagoda]

Indeed, but when I was rebuilding Rolls Royce diesels the factory recommendation was to use Hylomar NOT that horrible instant gasket sh, one of their products, on one side of the gasket. However, If the faces of the joint are good then grease on both sides is good.
Stu

tend to agree- Hylomar even when the 2 faces are clean. Not much - just enough to smear/dampen the gasket, then assemble. I would try to even out the tightening on a diagonal basis. I know it is not a cylinder head, but it's good practice and easy to achieve.

 

[mogmog2]

I'd use Silicone RTV, as I've always used on motorcycle engines and gearboxes.

Motorbike gubbins are right in front of you - rather easier to get to than the gearbox on a Centaur. I'm running with the traditional route on this one. Also Loctite state "do not apply heavy service loads for 7 days!". I'm bolting this on & firing her up!

 

[mogmog2]

tend to agree- Hylomar even when the 2 faces are clean. Not much - just enough to smear/dampen the gasket, then assemble. I would try to even out the tightening on a diagonal basis. I know it is not a cylinder head, but it's good practice and easy to achieve.

I always tighten diagonally. Only four bolts in this one though thankfully.
It would appear that the jury is split so I'll probably be ok either way.
General question for the pro-greasers: in your view is hylomar just another thing to buy and has no general advantage? Are there any applications where you would use it?
I was going to go with grease until the pro-hylomar chaps turned up! Old habits die hard and I feel a bit of an urge to use hylomar but the other part of me sides with the viewpoint that it is superfluous.

 

[elton]

Why use instant gasket, on a gasket

Because, when splitting casings the old gasket would often tear. Hard to explain unless seen. But the instant gasket would bridge the gap of the tear, and complete the seal.

 

[PaulRainbow]

Because, when splitting casings the old gasket would often tear. Hard to explain unless seen. But the instant gasket would bridge the gap of the tear, and complete the seal.

I know what you mean, but the grease stops the gasket tearing too, it's part of the point of using it.

 

[mogmog2]

I know what you mean, but the grease stops the gasket tearing too, it's part of the point of using it.

I understand that grease stops the gasket tearing on dismantling, but ideally a new gasket should be used each time? I've also done time scraping away gasket+sealant from flanges so can see why one would want to avoid that. I've also had to scrape RTV sealant away from both sides of a thing and that's not a whole lot better. In fact there was something silicone-like on the flange which needed a razor to remove.

Given the ease of making and low cost of this gasket and the aggro caused by any small amount of failure (oil dripping into the bilge), I want the best, not most convenient option: Grease stops it sticking, does it do anything else?
Hylomar presumably adds improved gap-filling to the seal (better), but makes it stick when dismantling.

If Hylomar gives any seal advantage, surely that's worth having, even at the cost of effort manana?

 

[RichardS]

Because, when splitting casings the old gasket would often tear. Hard to explain unless seen. But the instant gasket would bridge the gap of the tear, and complete the seal.

I don't understand why anyone would even try to re-use a gasket which tore on the previous dismantle.

Richard

 

[mogmog2]

I went with hermetite.

 

[elton]

I don't understand why anyone would even try to re-use a gasket which tore on the previous dismantle.

Richard

Because it was an unpressurised chamber, and the gasket was only to prevent oil leakage. Some gaskets are expensive.

 

[ghostlymoron]

Provided the two mating surfaces are true, the gasket will provide a perfect seal. I always use a smear of grease mainly to hold it in place whilst the joint is assembled.