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To RTV or not to RTV...

8K views 27 replies 14 participants last post by  sbchevfreak 
#1 ·
Okay, I have been reassessing several of my shade-tree mechanic practices from the past several years and the use of RTV has come up. My understanding / preference has always been to use only when necessary. That said, does anyone have a quick rule of thumb on when to use and when not to use?

Thanks!!
 
#2 ·
I use it one everything that wont see high heat or pressure (exhaust or head gaskets) on water pumps, oil pans, intakes, carb gaskets, valve covers, etc. Always use it.

Yes many people can get by without it, but its never CAUSED a problem for me and I've also never had the leak issues that I often hear of.
 
#9 ·
I use it one everything that wont see high heat or pressure (exhaust or head gaskets)....
Times are changing, this from Sanderson Headers, they do not recommend any gasket with their ceramic headers, this is a pert of what was included with my ceramic headers and turnouts, delivered today:

"Basic Installation Procedure

5. Install two studs, one in each end of the cylinder head to align the flange.Permatex Ultra-Black Sealer

6. Place a bead of Permatex® #82180 Ultra Black® Silicone (or compatible) at least 1/8" thick, maximum 1/4". Allow the silicone to set until dry.

7. Put the header into place. Install all header bolts finger-tight, the torque to 15-20 ft/lbs..."

This is a new one on me too, and has to do with their "New header flange technology..." :rolleyes:

Sanderson Header installation tips and upkeep on your Sanderson Headers.
 
#3 · (Edited)
A little goes a Long way. I use it all the time! What I like to do is apply it with an ink roller. I lay out the, paper, gasket on the card board backer,
the gasket comes with, lay a bead of silicone then roll it out thin. Both sides. I learned this trick sealing Bike engines together works awesome,
just roll it out on the case half's. Cleans up with a little WD-40.
Like anything, you got new on new, you probably don't need it but after somebody has pried it apart and left gouge's or good ole corrosion, well.........
I hate leaks just as much as my customers!
Hope this helps.:pimp:
 
#11 ·
None of our in-house transfercases and only some of our gearboxes have gaskets. We use Valco (brand) silver-colored RTV. Brand doesn't matter as much, however Valco makes a widget called a 'Tube-Grip'; its a plier-looking gizmo that can apply a very narrow, uniform bead; better than the caulking gun or 'cheez-whiz can' applicators. We use way less RTV, have a LOT less clean up time and don't have issues with the accidental gob of RTV.

Also of note: some RTV-type sealants have a lot of acetic acid which can out-gas and cause rusting if the unit sits too long without use. Is it critical? Not usually, but its something to think about if your project is going to sit a long time without turning it over. We'd prefer an Anerobic sealant, but a lot of our customers wouldn't buy it if we specified it anyway. Be careful on items that need a specific amount of backlash, some of these RTV-type sealants can expand a lot and change your dimensions.

http://www.valco-cp.com/Tube Grip Dispenser.htm

Thats the link to the Tube Grip; Valco also has Hylomar which is some interesting stuff for certain applications. It doesn't harden or set and can withstand some pretty wild temperature swings.

I'm not a Rep for Valco, but I thought I'd mention them as an alternative.
 
#12 ·
A couple "rules of thumb":

RTV is only used in the corners where pans/blocks/heads/manifolds "come together". Some engine families need the pan lips "beaded". NEVER on the pan "rails".

Two machined surfaces and a paper gasket, DRY, is the MOST effective way to seal.

If a little is enough, A LITTLE IS ENOUGH! A "lot" is NOT better.

Permatex "Ultra Black" is the only type (RTV) we use on internal engine parts. Not a "high temperature" sealant, I would avoid it on the headers. The red "High Temp" RTV is more desirable there.

Permatex "Aviation" is a brush-on sealant used around water outlets in heads, oil pump flanges, and other areas where minimum "thickness" of the glue is desired. It is also the sealant "of choice" for head bolts that go into water (Chevy, big Dodge, some Fords). Similar products you may be familiar with are "Indian Head", "Kopper Kote" (brush on) and Permatex "Super 300". "Aviation" is FAA-approved for use in internal combustion engines.

"The Right Stuff" (also a Permatex product) is quite popular these days. I don't like it, as it's too hard to "work" with.

Far-and-away the most problems we see with DIY builds, is too much sealant used. Sheet metal parts get damaged trying to get them off. Oil pumps die a horrible death when globs of RTV get sucked in. I've even seen a Rambler V8 with the oil passage from the pump to the block almost completely blocked, where no sealant AT ALL was needed.

We "glue" model cars together. Real ones use bolts... :)-

Jim
 
#13 ·
A couple "rules of thumb":
Permatex "Ultra Black" is the only type (RTV) we use on internal engine parts. Not a "high temperature" sealant, I would avoid it on the headers. The red "High Temp" RTV is more desirable there. Jim
I tend to agree Jim, but why would a major manufacturer like Sanderson specify it (Permatex RTV Black) to seal their header flanges? I questioned it too, but with the price of their headers, I feel the consumer should follow their directions, if for no other reason, warranty.
 
#21 ·
Pretty much X2 with Mr. P-Body. I'll add one place I never use RTV is a sealer for bolts that penetrate in to wet or oily places. My preference for the likes of Chevy head bolts and same/similar situations in other auto/machine brands is Teflon Plumbers Sealant.

P-Body where did you get " We "glue" model cars together. Real ones use bolts..." priceless!

Bogie
 
#14 ·
If its a pain to install your new headers, I would call Sanderson and ask. Although, there used to be a woman there that was...not customer friendly...to say the least; I cannot remember her name for the life of me, but I'd avoid her if you want an answer

I know, it sounds like a BS answer, but when we recommend something, I have no trouble explaining why we feel that strongly to the customer
 
#15 ·
If you use a sealer with a gasket only put the sealer/glue on the part surface not ht engine side. You will be happy you did it this way if you ever need to take it back apart. Most if not all of the gasket will stay on the removable part.
If you are just gluing a gasket for ease of install the 3M weather strip adhesive works great. I have used this for years on water pump and other troublesome gaskets.
 
#17 ·
There is no weather stripping in an engine. The use of it as a gasket sealer is NOT recommended. I used to see people use it a LOT to hold valve cover gaskets to the covers in "solid lifter" engines for adjusting. I've also seen innumerable valve covers destroyed trying to get that stuff off them. After you've had to clean up after this, you won't be so apt to recommend it.

FWIW

Jim
 
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#23 ·
No do not use RTV on older engines. It is only used on engines that call for it. My Q45 comes to mind it had a front timing chain cover with no gasket and required high temp orange/copper rtv to seal it up.

For valve cover gaskets rtv will make them leak do not use. Use either nothing for rubber gaskets or Indian Head gasket sealer for cork and paper gaskets. That is made for cork gaskets rtv is not.

Basicly toss the stuff in the trash and use what the manufacturer recommends. Never use rtv for anything that does not call for rtv in the shop manual. If you have a older chevy you dont need it at all.

I am stunned with all the back and forth and not one of them said to check the manual for the proper sealent. If you use rtv on paper or cork it will leak for sure. Maybe not today but by next year you will need new gaskets when they should have lasted the life of the car.

This is the magic juice. It works like crazy and forms a glue that will hold your gaskets in place while you install the part. just a lthin coat on each side of the gasket and it will tack up in a few minutes holding your gaskets in place as you turn the part over to install it. Helps a lot with heavy intakes and other parts that require fiddling that can move the gasket out of place.

Permatex 20539 Indian Head Gasket Shellac Compound, 2 oz. : Amazon.com : Automotive


RTM!!!!
I don't know man.... I've been using RTV for years on paper and never have had a problem, or I wouldn't use it.
I really think most over do it and that's why they have problems.
 
#19 ·
I use Ultra Black RTV always on SBC and BBC intake gaskets to replace the front/rear gaskets that I toss. Also use it on pan gaskets, timing cover gaskets, rearend cover, or thrid member. I never use it on transmission pan gaskets unless the gasket is not the self sealing type. Tried it with the black self sealing gaskets and it leaked like a sieve. Those type trans pan gaskets are made to react to trans fluid, and they wont work if you have RTV on them.
 
#20 ·
g.m used rtv allot,,
find me a 2.5ltr iron duke pan gasket/timing cover/etc.. there was none, not even when new, felpro made some and sometimes you can find them.. but g.m. shop manual calls for rtv.. no gaskets..
the glue, makes it a p.i.t.a. to remove, but leaks are non issue 99% of the time..
form-a-gasket is heaven, as long as your not doing the next r&r:welcome:
 
#24 ·
Another problem besides using too much is not allowing it to skin over per the instructions before installation. RTV in an uncured state is a lubricant; some gaskets can be squeezed right out from between the joint.

No harm in using it on paper. The taller and thinner the gasket w/long runs between fasteners, the less likely for a good result because of the chance of displacing the gasket from the joint that's being sealed- like a cork valve cover gasket. On a flat, wide surface- like a water neck gasket or a fuel pump gasket (paper, both) they will seal fine w/RTV should you choose to use it.

New/freshly machined gasketed flat surfaces are less likely to need any sealer- RTV or otherwise- unless the application or common sense dictates otherwise. Old, corroded, scratched and/or uneven surfaces can often benefit from using a sealant, RTV is among those that can work well.

I would never use RTV on a threaded fastener like head bolts. Permatex Aviation or #2 works well for me, other people prefer teflon sealers which also work fine.

BTW, most of us who've been doing this for a while understand what is meant when the word "Permatex" is used. Before there were OTC RTV sealers, Permatex (#1, #2, #3 and in cans) was one of the standards, along w/Indian Head and K&W Copper Coat.
 
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