Re:Gasket sealant, need everyone opinion.

[Hirsch <Catenary@xxxxxxxxxxxxxx>]

Dear Alfisti,

The use of RTV silicone as gasket material was discussed on this
digest before. Back in July '96 (AD 3019) the case for using
RTV sealants was made by Jim Steck, a well-regarded engine
builder from Ohio, USA. I've included his original post below.

Rich

P.S. It's good to see that Joel Hailey is once again posting
to the AD.
~~~~~
 From: Jim Steck <72614.557@domain.elided>
 Date: 24 Jul 96 15:50:46 EDT
 Subject: RTV gasket sealer

> my objection to RTV is that in all cases I've found its use
> excessie and because people tend to use too damn much, I say
> forget the damn stuff. Even used sparingly, it oozes out and
> can break off to plug oil passages.

 I agree that excessive amounts can cause _big_ problems ... but
 don't forget about the oil nozzles I use in my turbo engines ...
 the orifices are only 0.8 mm diameter. If they get plugged, the
 pistons overheat. I wouldn't use RTV if it caused problems. Any
 sealer used in excess can cause the same symptoms. Yet, assembling
 an engine without any sealer is a guarantee of big leaks.

 Here are a couple techniques I use to make sure there are no
 bits floating around inside my engines.

 1. Apply the RTV sparingly.  Use the applicator nozzle supplied
 with the tube. Cut it on a 45 degree angle at the 6 mm diameter
 step. On the 'point' of the nozzle, remove a 1.5 - 2.0 mm triangular
 notch. Hold the nozzle flat against the surface to be sealed as
 the tube is squeezed ... this way only a narrow ribbon of sealer
 is applied. One of the 'gun' type tools designed to squeeze the
 tube makes this operation easier.  =


 2. Let the sealer sit for 5-10 minutes before assembling. RTV
 cures after it absorbs moisture from the air.  If you
 immediately assemble the parts, the center of the joint
 may never completely cure.

 3. Assemble the parts and pull the bolts/nuts up with about
 1/2 the normal torque. Let sit overnight and then finish
 tightening. This put a compressive force on the cured gasket.

 4. Carefully inspect the inside of the joint for any traces
 of oozing sealer. In the unlikely event you find any, scrape
 and remove it. The timing cover surfaces are fairly narrow,
 and some 'oozing' may be found.  The oil pan rail is wide
 enough that 'oozing' is unlikely (and inspection is impossible).

 Obviously, it takes a couple days to assemble an engine.
 I use RTV in only a couple places ... in all cases without
 paper gaskets:
	timing cover
	oil pan
	cigarette seals (squirt some into the hole before installing the seal)
	rear cover - oil drain on back of block
	cylinder liners to the block (without the factory o-rings)
	water pump

 A couple other thoughts ...
 The surfaces must be absolutely oil free ... use brake cleaner.
 If your car has an oxygen sensor ... use only 'sensor safe' RTV.
 Do not use RTV to seal paper gaskets.
 If you use RTV at the base of the liners, put all the liners in first
 (without crank or pistons/rods) and hold them in place overnight with
 the head (use your old head gasket) torqued to 30-35 lb-ft.

 Form-in-place gaskets (RTV etc.) allow leak free metal-to-metal
 joints in the engine. This produces a stronger structure, and
 precludes creep in the joints ... which shows up later as a leak.
 MOST car manufacturers use RTV somewhere in there engines ...
 any fluids collected in during emissions testing are added to the
 tailpipe emissions when certifying a new car ... so the OEM's
 are _very_ picky about leaks.

 Jim Steck
 AutoComponenti
~~~~~=

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