I was putting a new water pump on my 99 Ram 1500 5.2 and the o-ring that came with the water pump did not seal. In fact it just disappeared once I put the heater pipe back in. I need to know what size the o-ring is, or where I can get one.

 

You can get them anywhere.. Advanced, Napa, Autozone.. they are common.. in fact.. Advanced and Autozone, and Napa sell the whole metal hose with the gasket O-ring attached for like 9 bucks... I usually will coat the O-ring with just a dab of lube.. like assembly lube or petrolium jelly...keeps it from ripping as you put the return tube back in the pump...but i haveseen one or two leak so..I usually put a SMALL bead of black RTV around the ring on both the underside and overside..when it slips in.. it makes a bead around the opening in the water pump, sealing the opening. I really dont like this though.. it can make the tube a real PITA to get out later if the pump goes again..

 

O-ring is 1/2" inside diameter.

 

Thanks, Blaydrnnnr. My step-son tried silicone instead of the o-ring. Do you think this will hold, or should I just get the new assembly.