Water Pump O-ring won't quit leaking

[Ncostello]

Recently, I noticed some coolant on the garage floor... a teaspoon amount perhaps. I tracked it up to the water pump and could see it leaking at the block/pump interface. With 200K on the original pump I decided to replace the pump as well as the o-ring gasket. The original gasket was hardened pretty good.



The new pump and gasket went on without any problems and all the surfaces were very clean and true looking. However I noticed I once again have the leak from the same location. I don't drive it much. I'd say the gasket held for about 6 months and then the leak returned. Will sitting cause the gasket to "shrink" or do I need to silicon the edges of the oring before I install a new one again? Or silicon the metal pump mating surface around the outer edge?

 

[cerberusiam]

Either silicone or other type of sealant on the flange works. Got the same problem on one truck and too lazy to fix it. Other one was no issue. Go figure.

 

[The patriot]

I've noticed one time the mating surface between the wp and block, there was a extremely small amount of bubbles coming out. Just one area the size of the head of a pin.

By extremely small, I mean if you dont have perfect vision, you wouldnt even see it.

I've never seen any on the ground, and have never had to add any antifreeze.

I'm sure it still bubbles at times, but I cant even see the tell take "dried antifreeze" color in the area. It was that small.

I owned this truck since new and I flush the coolant system every year and new antifreeze. I have about 128K miles. If it dont get bigger, I'm leaving it alone.

 

[HHhuntitall]

I see this quite a bit on the older trucks. The little rust that is there will cause the gasket to not seat just right, or there could be a little grit/rust between the block and seal or seal and pump. I usually silicone 'em just so I don't have a comeback. It doesn't take much, and it saves me the time of having to redo it!!

 

[Ncostello]

Thanks. At least the water pump on the 5. 9L Cummins is among the top 3 easiest in the world to remove/replace... of any vehicle. (1. Remove belt 2. Remove 2 bolts 3. Admire pump in hand)