The Perils of using Silicone Gasket goo

[Richard]

For no other reason than I like spending time in the garage wielding spanners, I started to strip down a C15 engine from an abandoned project that came my way, now the engine bar the primary side had been rebuilt by the previous owner using many new parts which came to me well documented. Apart from the tinkering side of it I always like to be sure that any bike I have is hopefully going to go well  and be as reliable as one can hope for, now as you can see from the pictures the previous builder had used silicone and if I had not taken it apart it would not have lasted long, the oil feed hole, which is the hole between the right hand pump nut and the crankshaft is full of silicone, not only that but some of that excess silicone would be trying to circulate around other parts as well.
Which is why I always shudder when someone says they use instant silicone gasket.I must confess I have used it once in desperation on my Super Rocket Rocker box as no matter what I did I could not get it oil tight, and then I smeared a small amount on using my finger needless to say in defence of the stuff the rocker box is now oil tight.
So if you do use it be carefull
Richard

[a10 gf]

 

Good topic, good example. Have always advised against such mess, but sometimes to no avail, beeing met with a sigh and smile. Some send their engine away for some overhaul, and get it back like the pic, and have to pay for it (several ways...).
e

[Triton Thrasher]

Is that silicone or Hylomar?  I only ask because it's blue and hasn't pulled off in twangy strings.  I wouldn't blame the product there: he's just used too much, granted that metering out the right amount onto such narrow surfaces is fiddly and a paper gasket would be better.  Why did they use any sealant at all on that rib that curls under the crank pinion, where the oil hole is?  There's no real leak opportunity there, except at the oil feed itself. 

They must have had to wipe off a similar excess from the outside of the engine, which should have made them think about what was happening on the inside.

[LJ.]

They must have had to wipe off a similar excess from the outside of the engine, which should have made them think about what was happening on the inside.

That's a very good thought and is an excellent measure to when I also apply ermmmm 'Silicon gasket goo' 

[Richard]

Yes it is silicone and I do not know why it was applied in such quantity, there is no gasket fitted between these two mating surfaces and the smallest amount of golden or similar sealer should have been applied, Hylamar is good stuff and I also use it but even that has to be applied very thinly as well

 I also apply ermmmm 'Silicon gasket goo'

LJ I thought you were a traditionalist and only used grease and gaskets!!
Richard

[Beezageezauk]

Hi Richard,

What can I say??  Well, quite a bit actually....starting with:-

 Don't knock the product....knock the user!!

The guy who built that engine has used far too much and hasn't taken care on the build up.

Now then, you know me...we've met and chatted...and you know the high mileage that I do on my A10's and B31.  I build my own engines and very rarely use traditional gaskets.  My toolbox contains a tube of silicon based "Instant Gasket" which is priceless when it comes to working on an engine, especially on a campsite!!  Not necessarily mine I hasten to add (but it has been known) and if anyone needs assistance I'm usually there.

Yes, I admit it.  I always use the stuff and I've never had a problem with it.  Now then, I can see the majority cringeing as they read this but I guess it's a case of "speak as you find".  Using it sparingly and away from oil holes shouldn't be a problem.

Beezageezauk.       

[Triton Thrasher]

  I always use the stuff
Beezageezauk.       

In many cases (haha- cases!), if you don't use either silicone rubber sealant or solvent-based compound such as Hylomar, you will have leaks.

Some may now chime in with "dry gaskets" and "gaskets with grease," but frankly, I've done it every way and am never without a mastic gun of bath sealant in my manbag these days.

[Richard]

Of course I have met you I think the last time was at Wickseed, trouble is the name eludes me but it might start with an A.
Anyway I certainly do not knock instant gasket it has its uses as I previously said I used it on the rocker box on the A10.
However the reason I shudder when someone says they use it is when I do not know the capabilities of that person then it is a worry.
The previous owner was a bit over enthusiastic applying it and I was really just trying to show the perils of the stuff, this would apply to some gasket sealers we all use like Hilmar if applied to thick.
I would certainly carry a small tube for breakdowns but in the workshop I would try not to use it unless all else had failed

[a101960]

Richard,

How many times do you reckon that we have had my timing cover off of my bike? Quite a few! and each time that same gasket has been reused with grease, and it still seals without any leaks.

John

[Richard]

Spot on John we have had that on and off a few times and each time we only used a smear of grease, I am hoping that the B40 Trials bike inner and outer cover will only require a smear of welseal on the inner to crankcase as there is no gasket on that face and a gasket and grease between the outer and inner, as I have spent a bit of time with the glass and the grinding paste lapping the surface's.
The C15 will have the same treatment when I put the engine back together.
While I am on the subject has anyone got or know of a link for a free download of the parts list and service manual for a 1965/66 B40?
Richard

[RichardL]

Man, we have been around this topic a lot. I think there are personal favorites that, no matter how much advice one gets to the contrary, we can't be swayed off those favorites. I don't use the grease approach, because I figure the surfaces are less than perfect and that paper gaskets don't compress enough. I don't use silicone (any more) where it can get in the oil, because I have, indeed, found some where it shouldn't be (but not on my bike), though, works fine on the primary cover.

Look at the following quote regarding Blue Hylomar uses. I think it is interesting by its omission of any recommended uses wherein a broken-off bit can foul an oil passage.

Suggested Applications: Thermostat housings, differential coverings, hydraulic drives and motors, gearbox assemblies, intake manifold assemblies, oil, fuel and water pump housings and seals, fuel injectors and fuel pumps, transmission and torque converter seals
 
(Well, maybe it does say "oil pump housings," but I'm not convinced.)

As for myself, I like the following old-fashioned sealer:

Permatex® Form-A-Gasket® No. 2 Sealant

Slow-drying, non-hardening sealant designed for sealing cut gaskets and stamped parts. Allows for easy disassembly if required. Temperature range -65°F to 400°F (-54°C to 204°C); resists common shop fluids and fuels. Use where sealing is more important than adhesion.

Suggested Applications: Valve cover gaskets, oil pan gaskets

...and I also use:

Permatex® Ultra Rubber Gasket Sealant & Dressing

Formulated specially for rubber gaskets, it conditions gaskets for longer life and seals potential leak paths. It also functions to hold gaskets in-place during installation. The non-hardening, soft-setting formula makes gasket repositioning quick and easy. Provides outstanding oil and fluid resistance. Temperature range -65°F to 400°F (-54°C to 204°C).

Suggested Applications: Designed for use on all cut and formed rubber gaskets, but also great to condition and extend the life of composite, paper and cork gaskets.

Richard L.

(I'm just going to post, despite the post while I was typing.)

[Beezageezauk]

Hi Richard,

There is a C15/B40 Parts List and Service Sheets on CD available on Ebay.  It doesn't state what years it covers but you can check it out by searching for 260504318080.  It won't be expensive and the seller might be reproducing them if you don't want to bid for it!!

Sorry to deviate from the thread.

Beezageezauk.

[jfligg]

Hi Guys
           I use a product call 3 Bond.  It dries to a soft coating.  I apply it with a paint brush (sparingly) on both halves then assemble.  I find it works reall good.  Jeff

[Samson]

I agree with the above. Ok to use it sparingly. when you consider the time involved in a rebuild a little insurance dose no harm.

[rocket man]

when i put the silicone on i put a thin bead on the top of gasket then i use my finger and smear it
leave it to dry for 5 mins turn gasket over and do the same on that side then There is less chance
of it leaving blobs when cases are tightened up


dave