Water from A/C dripping on exhaust?

White LTZ · June 12, 2024

I've had my 2023 AT4 with the 6.2 since late August. I love the no truck and no issues so far except the occasional annoying slow software startup or the a/c fan turning itself down a couple of minutes after starting the truck. Today after an uneventful drive home from work I park in my garage as usual. After exiting the truck and walking toward the house I start hearing an unusual noise. It is a sizzling sound every few seconds. I start looking under the truck and see water dripping down the driver's side of the transmission pan onto the exhaust line that passes under the pan. I've never heard or seen that before. Is it possible my drain from the evaporator is plugged? I'm guessing it is water from the A/C. No rain in a few days here and no puddles. Also, I saw no water dripping in the usual spot passenger side just forward of the cab. I've attached a picture that shows water collecting on the exhaust line after it cooled down enough to stop cooking it off. It is hard to see in the picture but appeared to be collecting and dripping onto the exhaust just forward of the pan bolt in the picture. Has anyone else noticed this? Also, this is the first time I've climbed under the truck. That exhaust pipe is rather flat top and bottom. Is that normal? I have not hit anything while driving or been off road. There are no marks on any of the other skid plates, framework, or lower front fascia.

2016 Sierra Owner · June 12, 2024

34 minutes ago, White LTZ said:

I've had my 2023 AT4 with the 6.2 since late August. I love the no truck and no issues so far except the occasional annoying slow software startup or the a/c fan turning itself down a couple of minutes after starting the truck. Today after an uneventful drive home from work I park in my garage as usual. After exiting the truck and walking toward the house I start hearing an unusual noise. It is a sizzling sound every few seconds. I start looking under the truck and see water dripping down the driver's side of the transmission pan onto the exhaust line that passes under the pan. I've never heard or seen that before. Is it possible my drain from the evaporator is plugged? I'm guessing it is water from the A/C. No rain in a few days here and no puddles. Also, I saw no water dripping in the usual spot passenger side just forward of the cab. I've attached a picture that shows water collecting on the exhaust line after it cooled down enough to stop cooking it off. It is hard to see in the picture but appeared to be collecting and dripping onto the exhaust just forward of the pan bolt in the picture. Has anyone else noticed this? Also, this is the first time I've climbed under the truck. That exhaust pipe is rather flat top and bottom. Is that normal? I have not hit anything while driving or been off road. There are no marks on any of the other skid plates, framework, or lower front fascia.

It's been that way since these trucks came out in 2019. There are a few posts about it already. The exhaust pipe is also designed that way on all of these trucks.

Edited June 12, 2024 by 2016 Sierra Owner

Bikerjon · June 12, 2024

32 minutes ago, White LTZ said:

I've had my 2023 AT4 with the 6.2 since late August. I love the no truck and no issues so far except the occasional annoying slow software startup or the a/c fan turning itself down a couple of minutes after starting the truck. Today after an uneventful drive home from work I park in my garage as usual. After exiting the truck and walking toward the house I start hearing an unusual noise. It is a sizzling sound every few seconds. I start looking under the truck and see water dripping down the driver's side of the transmission pan onto the exhaust line that passes under the pan. I've never heard or seen that before. Is it possible my drain from the evaporator is plugged? I'm guessing it is water from the A/C. No rain in a few days here and no puddles. Also, I saw no water dripping in the usual spot passenger side just forward of the cab. I've attached a picture that shows water collecting on the exhaust line after it cooled down enough to stop cooking it off. It is hard to see in the picture but appeared to be collecting and dripping onto the exhaust just forward of the pan bolt in the picture. Has anyone else noticed this? Also, this is the first time I've climbed under the truck. That exhaust pipe is rather flat top and bottom. Is that normal? I have not hit anything while driving or been off road. There are no marks on any of the other skid plates, framework, or lower front fascia.

Both normal conditions. A/C drains onto the trans and drips onto the exhaust pipe. Exhaust pipe below truck is semi-flat shaped. Engineers claim this causes no restriction in the exhaust flow. All the newer 1/2 tons are like this.

White LTZ · June 12, 2024

OK. Thanks to both of you for the replies. I guess I just never noticed the sizzling sound before. And my first thought if that was the normal shape of the exhaust pipe is that would seem to be restrictive. I'm sure the engineers know better than me.