I own a 2005 GMC Envoy(4200 Vortec Inline 6) and we are doing water pump installation. But my question is is it necessary to use R.T.V on the gasket?

Nice going Robert. The Envoy doesn't even have an idle air control valve. IT's an electronic throttle body. And Petosin is NOT approved for use in this engine. And no, Bosch plugs will NOT get 20% more gas mileage compared a to comparable AC plug.

As for the RTV. If you use it, use it sparingly. Most DIYers put on too much. Then it breaks off and clogs radiator and heater core tubes.

GHOOD QUESTION! HIS "atlas" ENGIEN IS PRETTY MUCH MADE LIKE A COMPARABLE toyota OR bmw DOHC ENGINE IS MADE! great ENGINE. i WOUD Lnot USE ANY GASKETING rtv SEL;ANT ON IT! pERHAPS A SMAL;L DOSE OF hylomar! sINCE all EURO CARS DO not REQURIE SEALANTS, i WOUDL not USE IT ON YOUR WATER PUMP! <<> READ THE "DEXCOOLSETTLEMENT.COM" WEBISTES AND SEE WHY gM FILLED FOR BANKRUPTCY, AS NEARLY all THEIR ENGIENS MADE FROM 1996-2003 AND EVEN TO 2005 WILLL DEVELOP cooling system PROBLEMS AS dexcoolo EATS HOLES IN gm GAK\SKETS, AND dissolves PLASTIC INTAKE ASSEMBLIES! i use only audi pink OR rose COOLANT IN any GM ENGINE! eVEN gm IS NOW USING audi/pentosin pink COOLANT IN THE cruze DIESEL AND THE buick turbo gas EURO ENGINE! <<> use Amsoil Power foam ON YOUR idle air control valve AND throttle body< AND USE bosch OR denso iridium plugs TO GAIN UP TO 20% MORE IN POWER AND ECONOMY AS WELL. also USE mobil one "0"SERIES OIL AS IN, 0w-=30 OR 0w-20 OIL! Your "Atlas" ENGINE CAN LAST INDEFINITELY WITH a|small CHANGES IN IT! Most ATLAS engines get bad converter and o2 sensors codes! Using BOSCH or DENSO iridium fixes this, and a clean IAC will keep the AIR?FUEL ratio in order around town to save on GAS! GOOD LUCK! DEXCOOL is just NO GOOD! BYE NOW!

Nope, doesnt require sealant

Personally, I have found that rubbing the gasket down with silicone grease works better then RTV as long as the mating surface is defect free.

I own a 2005 GMC Envoy(4200 Vortec Inline 6) and we are doing water pump installation. But my question is is it necessary to use R.T.V on the gasket?