I had the truck idling on a steeper slope the other day and noticed condensation water dripping out of the back of the muffler. Right above the seam at the bottom rear is a hole.
Is there supposed to be a drain hole there, or is it starting to rust through?

It is a '99 with 150K....

 

think its a drain hole for that exact reason...

 

The engineers at Ford call that a "tinkle hole"...

 

yup theres one in my03 as long as its draining its ok

 

The byproducts of the catalytic converter include water. And it condenses in the colder muffler.

Yeah, there's a drain hole

 

It's even more basic than that. The output of hydrocarbon combustion from any engine is CO2 and H2O, with other things thrown in (like CO and NOx and unburned hydrocarbons) as the process is never perfect or always right at stoichiometric ratios. The cat is to help that process get more towards perfect by cleaning up the "mess" downstream of the engine.

The drain hole is to prevent water from building up in there and causing corrosion, especially when it is cooler out and the water condenses in the muffler.

 

It's mainly to prevent the muffler from corroding. They have been putting those holes in there since they invented the cat.

 

Thanks guys. I've never noticed any of my other vehicles tinkling, but this is the first time I've seen a muffler mounted on it's side with the outlet on top. Definitely an arrangement that will accumulate water.

Of course, now I have to question why the tinkle hole is on the UPHILL end of the muffler. These trucks all seem to come from the factory with the rear higher than the front. The front of the muffler will still hold plenty of water unless parked uphill on a pretty steep slope....

 

I'd think the drain hole needs to be baffled. If it was in front, it would let out unbaffled exhaust, wouldn't it?

 

I think they are all in the back because of the direction of flow and the hole is so small that it doesn't contribute to any noise or fume problems.