How to use Silicon gaskets? - - Excellence in Motion
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post #1 of 6 (permalink) Old Jul 9th, 2009, 1:58 pm Thread Starter
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Smile How to use Silicon gaskets?


This might seem naive /stupid but after spending a long time reading all kinds of specs I still do not understand how critical it is to use EXACTLY the silicon gasket recommended by BMW.

In my case using Three bond 1207b for the oil pan (sump) on my 1987 K100 but issue is larger.

I have 3 questions:

1) This is unavailable here but I have "American Eagle RED RTV silicon Gasket maker" - how critical is it to use ONLY what the BMW engineers say?

2) what is the basic difference between black and red? what do the colors signify?

3) VERY important, how exactly to apply, given that surfaces are clean and dry. Should I wait for it to dry completely before reassembly? if not then what should I do? Should I smear an even thin film (like with an old credit card?) or put a tube of the material on surface?

Tnx for having the patience to answer what may be very obviouse to you but not trivial to a beginner like me.


Thank you,
1987 K100 (8V)
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post #2 of 6 (permalink) Old Jul 9th, 2009, 3:50 pm
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Over the years I've used Permatex RTV in Orange, Blue, Black, and Gray. They all do the job with minor differences. One is better for contact with fuels, one is better for high heat applications, one is safe for O2 sensors, etc.

Read the label carefully, but I think that most recommend a thin layer on both surfaces, then finger tight on the bolts, then final torque after the silicone has firmed up.

Don't use too much or you get lot's of excess squeezing out of the joint, sometimes in places where you don't want it.

I don't think it's important to use the exact brand recommended by BMW. Just make sure the stuff you use is correct for your application (oil, fuel, water, air, heat, etc.)
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post #3 of 6 (permalink) Old Jul 9th, 2009, 6:20 pm
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I don't think the gasket brand is as important as the preparation and application.

When I rebuilt my KRS I had to use the gasket compound in a few areas around the water/oil pump and sump areas.

First I made sure that both surfaces were absolutely grease/oil free. This is difficult with a motor in the frame and oil working its way downwards. My motor was out of the frame and upside down so I was looking down on the sump. Even so, I used brake cleaner to degrease the surfaces.

The silicon gasket I used came in an aerosol style can with a trigger - great for running continuous beads just like they show in the 'make your own gasket' pics. I cut the plastic nozzle to give a very small bead around 1/8" diameter. BMW machine to quite high tolerances and it's tempting to use far too much and get it spreading inside the internals. One gasket product I used came with a much wider nozzle so I plugged it with some steel rod drilled for a 1/8 hole. I laid a continuous bead on one surface only and left it a few hours to cure. Then gently prodded all around making sure it had stuck to the metal surface. I mated the two halves and didn't get any leaks afterwards.

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post #4 of 6 (permalink) Old Jul 12th, 2009, 1:52 am Thread Starter
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thank you both for the explanation.

I refit the oil sump cover paying a lot of attention to cleaning surfaces very well (some abrasive paper, and degreasing with contact cleaner and then wiping with newspaper).
I then put the material on the bottom half (too much i am afraid as a little came out wheni fit bolts - which probably also happened inside).
I then put the bolts in lightly and evenely - waited some 20 minutes and then toequed to the required 7NM (13! bolts i think)

I used dreibond 1209 as that is what I had.

I will soon run eng (cannot ride - waiting to locate goos 2nd hand rear drive) and will see if job was good enough.

Thank you,
1987 K100 (8V)
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post #5 of 6 (permalink) Old Jul 12th, 2009, 9:40 am
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I have another solution I used on the sump. You can't do it on the oil pump, but sump and timing cover are up for it:

I have a roll of 3mm nitrile rubber and make my own 'proper' gaskets. That worked a treat, is a lot less messy and guaranteed me a leak free result.

The only reason for all this silicone goo is it makes for faster cheaper factory assembly. I don't think it has any other benefit over a quality nitrile or silicone sheet gasket cut to shape.

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post #6 of 6 (permalink) Old Jul 12th, 2009, 3:45 pm
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The correct product will be an ANAOEROBIC gasket maker, easily available from many different suppliers,does not have to be Three Bond, I just bought some Permatex .Anaoerobic means that it cures in the absence of air. I would never use a sillycone type product on a motorcycle, the stuff has a bad tendency to squish out, no problem outside the engine but a mess to clean, but will later find little bits of red or blue sillycone all through your engine, maybe even plugging oil passages or the oil intake screen......bad news. Do yourself a favor , get the right stuff, it is a lot easier to use than sillycone.As far as I am concerned, sillycone only had one great use (Big or Bigger!!!) and even some of those failed too.

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