Cowl drain udders
Cruising
Joined: Mar 2018
Posts: 12
Likes: 1
From: Florida
Well I had read a number of windshield wiper motor threads and the general recommendation was to make sure the drain udders on the driver’s side under the cowl were not clogged. Always made a mental note to check mine but never seemed to get around to it and not having a wiper problem it never became a priority either. Today I just happen to be cleaning leaves out of the cowl area and by chance decided to at least check them out. Wow, both were solidly clogged and filled with water. Thanks goodness the water had not yet backed up to the level of the cowl and the wiper motor. So the moral of the story is don’t put it off and make it a regular routine maintenance item. It is easy to do and could save you not only some money but the aggravation of dealing with non working wipers or ones that won’t shut off. Just a thought.
Melting Slicks
Joined: Mar 1999
Posts: 3,211
Likes: 167
From: Rochester Hills Michigan
I ripped all my f’n drivers side ones out after constant flooded motors even after clipping….all good now in heaviest rains!!👍🏻
Last edited by RedC5; Aug 17, 2025 at 07:57 PM.
Cruising
Joined: Mar 2018
Posts: 12
Likes: 1
From: Florida
Found water on driver side after rain. Thought it had to have some thing to do with rain drains. Had similar issues with other cars I've owned. Had no clue where these are on my c5. Searched all over with no success. Thanks to everyone on this forum I found out where to look. Found the so called rain utters including the passenger side. The drivers side were all completely clogged up with what looked like damp mud. These had to be the cause of the water on the driver side floor. I was going to check passenger side but could not find my 8mm wrench to detach battery cables. My 8mm socket was too big to get into the space. Instead I removed the battery hold down and was able to move the battery aside enough to get my hand in there to remove this udder. It had some mud in there too but nowhere near the amount in all 3 driver side utters. Looking forward to a dry driver side carpet next time it rains.
Thanks to everyone.
Thanks to everyone.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
WHAT EVER YOU DO, DO NOT pull the passengers side cowl drain out of where it lives. It will come out but you will play hell getting it back into its proper place
Just pop it out of the cowl and blow it out with a garden hose. If there is anything in it, it will easily flush out of the bottom. It easily pops back into its hole in the bottom of the cowl.
The reason that GM put the weird, shaped tip udders on the cowl drains is to prevent under hood heat, vapors, gasses and smells from entering the cowl area. The cowl area (trough) is where the HVAC collects it outside fresh air when you are not in recirc mode. The lips on the ends of the udders close together when not draining water. With out the udders, the hot under hood air can get sucked into the cowl/HVAC outside air intake.
The C6 does not have udders. It has a slim rectangular shape opening on either side of the cowl with a flap to allow water out.
The C5 does NOT have a HVAC fresh air intake filter to filter out dust, dirt, pollen and junk in the air. The C6 has a filter
Don't forget about the HVAC Air Box Drain on the firewall. It too has a little 1/2" rubber 90 deg boot with lips that let the water out. The lips restrict how much fresh air comes out of the air box drain. Without the little rubber 90-degree rubber boot with the lips, a significant amount of cold air exits the airbox though that open 1/2 hole into the engine compartment.
The lips of the boot can stick together and prevent that air box condensate water from draining out of the airbox. If it can't drain out, it WILL DRAIN INTO THE PASSENGERS FOOT WELL directly on the BCM. NOTE!! The BCM does NOT like water!! If you see fresh clean water dripping out from under the passenger's side of the car where the firewall is when the AC is running, that's normal and desired/expected. If you do not see condensate water draining out when the AC is running, I highly recommend checking that drain boot and the drain tube. They can clog up with a snot type of slime and stop water from properly draining out of the air box.
The udders easily pop out and back into the underside of the cowl. On the rear of the fender liner (both sides)
is a removable access panel that can be removed to get proper access to that area.
BC
Just pop it out of the cowl and blow it out with a garden hose. If there is anything in it, it will easily flush out of the bottom. It easily pops back into its hole in the bottom of the cowl.
The reason that GM put the weird, shaped tip udders on the cowl drains is to prevent under hood heat, vapors, gasses and smells from entering the cowl area. The cowl area (trough) is where the HVAC collects it outside fresh air when you are not in recirc mode. The lips on the ends of the udders close together when not draining water. With out the udders, the hot under hood air can get sucked into the cowl/HVAC outside air intake.
The C6 does not have udders. It has a slim rectangular shape opening on either side of the cowl with a flap to allow water out.
The C5 does NOT have a HVAC fresh air intake filter to filter out dust, dirt, pollen and junk in the air. The C6 has a filter
Don't forget about the HVAC Air Box Drain on the firewall. It too has a little 1/2" rubber 90 deg boot with lips that let the water out. The lips restrict how much fresh air comes out of the air box drain. Without the little rubber 90-degree rubber boot with the lips, a significant amount of cold air exits the airbox though that open 1/2 hole into the engine compartment.
The lips of the boot can stick together and prevent that air box condensate water from draining out of the airbox. If it can't drain out, it WILL DRAIN INTO THE PASSENGERS FOOT WELL directly on the BCM. NOTE!! The BCM does NOT like water!! If you see fresh clean water dripping out from under the passenger's side of the car where the firewall is when the AC is running, that's normal and desired/expected. If you do not see condensate water draining out when the AC is running, I highly recommend checking that drain boot and the drain tube. They can clog up with a snot type of slime and stop water from properly draining out of the air box.
The udders easily pop out and back into the underside of the cowl. On the rear of the fender liner (both sides)
is a removable access panel that can be removed to get proper access to that area.
BC
Last edited by Bill Curlee; Aug 17, 2025 at 08:56 PM.
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Uneducated autodidact
Joined: Feb 2001
Posts: 5,411
Likes: 252
From: West of the Sabine, Texas
WHAT EVER YOU DO, DO NOT pull the passengers side cowl drain out of where it lives. It will come out but you will play hell getting it back into its proper place
Just pop it out of the cowl and blow it out with a garden hose. If there is anything in it, it will easily flush out of the bottom. It easily pops back into its hole in the bottom of the cowl.
The reason that GM put the weird, shaped tip udders on the cowl drains is to prevent under hood heat, vapors, gasses and smells from entering the cowl area. The cowl area (trough) is where the HVAC collects it outside fresh air when you are not in recirc mode. The lips on the ends of the udders close together when not draining water. With out the udders, the hot under hood air can get sucked into the cowl/HVAC outside air intake.
The C6 does not have udders. It has a slim rectangular shape opening on either side of the cowl with a flap to allow water out.
The C5 does NOT have a HVAC fresh air intake filter to filter out dust, dirt, pollen and junk in the air. The C6 has a filter
Don't forget about the HVAC Air Box Drain on the firewall. It too has a little 1/2" rubber 90 deg boot with lips that let the water out. The lips restrict how much fresh air comes out of the air box drain. Without the little rubber 90-degree rubber boot with the lips, a significant amount of cold air exits the airbox though that open 1/2 hole into the engine compartment.
The lips of the boot can stick together and prevent that air box condensate water from draining out of the airbox. If it can't drain out, it WILL DRAIN INTO THE PASSENGERS FOOT WELL directly on the BCM. NOTE!! The BCM does NOT like water!! If you see fresh clean water dripping out from under the passenger's side of the car where the firewall is when the AC is running, that's normal and desired/expected. If you do not see condensate water draining out when the AC is running, I highly recommend checking that drain boot and the drain tube. They can clog up with a snot type of slime and stop water from properly draining out of the air box.
The udders easily pop out and back into the underside of the cowl. On the rear of the fender liner (both sides)
is a removable access panel that can be removed to get proper access to that area.
BC
Just pop it out of the cowl and blow it out with a garden hose. If there is anything in it, it will easily flush out of the bottom. It easily pops back into its hole in the bottom of the cowl.
The reason that GM put the weird, shaped tip udders on the cowl drains is to prevent under hood heat, vapors, gasses and smells from entering the cowl area. The cowl area (trough) is where the HVAC collects it outside fresh air when you are not in recirc mode. The lips on the ends of the udders close together when not draining water. With out the udders, the hot under hood air can get sucked into the cowl/HVAC outside air intake.
The C6 does not have udders. It has a slim rectangular shape opening on either side of the cowl with a flap to allow water out.
The C5 does NOT have a HVAC fresh air intake filter to filter out dust, dirt, pollen and junk in the air. The C6 has a filter
Don't forget about the HVAC Air Box Drain on the firewall. It too has a little 1/2" rubber 90 deg boot with lips that let the water out. The lips restrict how much fresh air comes out of the air box drain. Without the little rubber 90-degree rubber boot with the lips, a significant amount of cold air exits the airbox though that open 1/2 hole into the engine compartment.
The lips of the boot can stick together and prevent that air box condensate water from draining out of the airbox. If it can't drain out, it WILL DRAIN INTO THE PASSENGERS FOOT WELL directly on the BCM. NOTE!! The BCM does NOT like water!! If you see fresh clean water dripping out from under the passenger's side of the car where the firewall is when the AC is running, that's normal and desired/expected. If you do not see condensate water draining out when the AC is running, I highly recommend checking that drain boot and the drain tube. They can clog up with a snot type of slime and stop water from properly draining out of the air box.
The udders easily pop out and back into the underside of the cowl. On the rear of the fender liner (both sides)
is a removable access panel that can be removed to get proper access to that area.
BC
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
If you cut the ends, you risk sucking in hot stale under hood air, possibly contaminated with carbon monoxide and under hood smells.
IMHO, I would leave them uncut and just check the driver's side udders whenever I wash the car. (Thats more than enough to keep them clean). I find that the one passengers side tube stays pretty much clean.
If I can fit my fat *** hand and arm in the space between the clutch Master cyl and hood latch and touch all three udders, anybody can. If you have an automatic C5, its that much more accessible.
Melting Slicks
Joined: Mar 1999
Posts: 3,211
Likes: 167
From: Rochester Hills Michigan