For most things that will leak, if given a chance, I use the Ultra
Grey Silicone. The formulations of RTV have changed over the years,
and the Grey is about the best yet, IMO. The grey stuff is sensor
safe, if that matters. On things I do take off regularly, like valve
covers, pushrod covers, timing covers, I do use the Hylomar sold by
Permatex. It's soft, wet, and can be used on old gaskets. If all I
want to do is pop off a valve cover to check the clearances, I can
do that and just reapply some Hylomar. The stuff cleans off easily.
I use the Silicone on the oil pan, which doesn't come off as often
and WILL leak big time without it. For things that really don't
come off often, I use the Ultra-Copper spray. This stuff is even
good on head gaskets. It's a lot harder to separate and clean off
though.
The disadvantage of the Silicone is that things have to be pretty
clean and dry for it to set up. The Ultra-Copper spray has an
advantage there. It's very quick setting. Parts with Hylomar on
them can also go back in service immediately. For my valve cover
and side cover, I use Copper spray on one side, and Hylomar on the
other side of the gasket. I glue it strongly to the cover.
For tranny cases, I was told the Loctite Anaerobic Gasket Maker,
or Yamabond were the hot items, but I had a pro work on my box, and
it leaked after he used an anaerobic sealer on it. I put it back
together with the Grey silicone, and no more leak. Go figure.
BTW, I still cut gaskets and apply "stuff" to them. Unless you have
perfect mating surfaces, the modern gasket replacements may leak.
The Silicone can fill larger imperfections, but you don't want pieces
of excess Silicone floating around in the system.
YMMV
Derek Harling wrote:
>
> Thought I'd get smart and check, since we are in a new millennium, which
> products are now considered best for engine rebuilding. Found the
> Permatex web site and found about 6 different RTV type sealers all
> recommended for sealing the same or almost the same components. Local
> distributor only carries the black - "Don't need anything else".
>
> What do listers recommend - red, blue, black, gray, copper . . . . ? -
> and Why? (I assume the various colors aren't just to match the engine
> color!)
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