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#2226482 - 04/08/11 07:33 PM Thermostat Gasket....Sealant?
doitmyself Offline

Registered: 06/03/02
Posts: 5587
Loc: MI
Hate to revisit this topic, but there seems to be no consensus about thermostat gaskets and sealant.

Some swear to use no sealant.

Others say absolutely no RTV with gasket (Permatex has a thermostat/water pump version).

Permatex #2 is mentioned a bit, along with a host of others.

Comments/opinions/experience for the shade tree mechanic? How does one make a decision??????

#2226485 - 04/08/11 07:36 PM Re: Thermostat Gasket....Sealant? [Re: doitmyself]
Quest Offline

Registered: 12/19/04
Posts: 7357
Loc: beaver land EH?
yes, I use permatex #2 for fibre based gasket.

I use nothing for rubber o-ring type gasket (like all Honda thermostats).

"Internet discussion boards act as echo chambers for conspiracy dittoheads" A.Allen

#2226536 - 04/08/11 08:07 PM Re: Thermostat Gasket....Sealant? [Re: doitmyself]
01rangerxl Offline

Registered: 04/08/06
Posts: 8961
Loc: Birmingham, AL
I used a paper Felpro gasket and a can of some Permatex spray on gasket sealant when I changed the t-stat on my truck. No problems after two years.
2002 Ford Ranger XLT | 3.0 V6 / 5-Speed Automatic / 2WD | 193K miles
1994 Ford Ranger STX | 4.0 V6 / 5-Speed Manual / 4X4 | 186K miles

#2226539 - 04/08/11 08:11 PM Re: Thermostat Gasket....Sealant? [Re: doitmyself]
mechanicx Offline

Registered: 10/23/09
Posts: 8576
Loc: Ohio
I think unless you are trying to cover up for a pitted housing or base that can't be easily replaced, it's best to not use RTV or gasket sealer and just use the paper gasket. Some applications used a RTV originally but usually the new thermostat will have a fiber gasket. With a rubber 0-ring seal you wouldn't use sealer of course.

#2226579 - 04/08/11 08:44 PM Re: Thermostat Gasket....Sealant? [Re: doitmyself]
onion Offline

Registered: 02/04/07
Posts: 2097
Loc: kansastan
For me it depends on the gasket.

If it's a good thick quality gasket, I usually don't use any sealant.

If it's a cheap, thin, porous gasket, I prefer a thin coat of Permatex #2 or anaerobic sealant (Locktite 504 or the like). But really just about any sort of gasket-goop will work. RTV, hi-tack, hylomar... they all work well enough. Just make sure you clean the gasket surfaces well and don't over-tighten the bolts, especially when using sealant... makes it much easier for a gasket to squish out.
The invisible and the imaginary look exactly the same.

#2226603 - 04/08/11 09:04 PM Re: Thermostat Gasket....Sealant? [Re: doitmyself]
eljefino Offline

Registered: 06/15/03
Posts: 30383
Loc: ME
+1 for Onion, couldn't say it better myself.

Thermostat gaskets have gotten a lot better; the o rings are fantastic and the big-hole-with-two-small-holes-180-degrees-apart ones are getting thicker and rubberier, making up for slight warpings of the always-poorly cast housing.

#2226605 - 04/08/11 09:06 PM Re: Thermostat Gasket....Sealant? [Re: doitmyself]
beast3300 Offline

Registered: 12/24/09
Posts: 3142
Loc: Ohio
Except O-ring seals with PITA placement: some gorilla snot (3m weatherstrip adhesive) to hold gasket in place.

O-ring seal: no glue/rtv.
'03 Regal GS L67: PP 5w30/FU3980

'99 Grand Prix L36: QS HM 5w30/STP 3387A E-core, Filtermag

'07 LaCrosse L26: PG 5w30/ProSelect 21040


#2226725 - 04/08/11 11:12 PM Re: Thermostat Gasket....Sealant? [Re: doitmyself]
Merkava_4 Offline

Registered: 01/30/07
Posts: 15373
Loc: Clovis, CA
For a fiber or cork gasket I use Permatex 2B.

#2226765 - 04/09/11 12:47 AM Re: Thermostat Gasket....Sealant? [Re: doitmyself]
Gearhead Offline

Registered: 04/05/09
Posts: 50
Loc: WV
If a rubber o-ring, I'd just go with that style only.

I've used The Right Stuff for all my sealing needs, oil, coolant, gear oil, ect., not had a single failure in 12 years. I used it just recently on a 91 S10 with a 2.5L iron duke thermostat housing, running a 1/8" bead on a clean dry surface, no other gasket material. The engine is notorious for weeping with replacement fiber thermostat gaskets. 15,000 miles/9 months and completely dry. Right Stuff is not a silicone sealant, it's an elastomer-rubber compound.

Key, a good scrape with a razor & wipe with brake cleaner is what I use.

Edited by Gearhead (04/09/11 12:47 AM)

#2226769 - 04/09/11 12:52 AM Re: Thermostat Gasket....Sealant? [Re: doitmyself]
mechtech2 Offline

Registered: 09/05/06
Posts: 19479
Loc: Chicago Area
I can't take a chance on a leak.
So even with nice 'O' ring types, I generally use a light smear of RTV.
Old parts are not as nice as new ones.

#2226927 - 04/09/11 09:22 AM Re: Thermostat Gasket....Sealant? [Re: mechtech2]
onion Offline

Registered: 02/04/07
Posts: 2097
Loc: kansastan
Originally Posted By: mechtech2
I can't take a chance on a leak.
So even with nice 'O' ring types, I generally use a light smear of RTV.
Old parts are not as nice as new ones.

I agree. If the surfaces are in good condition, I don't put any sealant on o-ring type seals. But when dealing with old, corroded and/or low quality parts, a little gasket-goop will avoid problems.
The invisible and the imaginary look exactly the same.