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Repair Guide: DIY: A/C Evaporator drain plug un-clog (no tools required!)

  #1  
Old 06-26-2010, 05:16 PM
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Location: OKC, OK
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Thumbs up DIY: A/C Evaporator drain plug un-clog (no tools required!)

I own a 1998 MC with a 3.1l motor that I have taken care of since it was a baby at 54k miles. One day, I noticed a sound coming from behind the dash of water sloshing side to side when cornering. The sound progressively got worse, getting louder and also sloshing when accelerating and decelerating. I noticed that it was only happening when I had the a/c on, so between that and the fact that my coolant level had not moved in months, I ruled out the idea that it was a plugged heater core.

I originally posted my problem here: Sound of water flowing when giving car gas. - Monte Carlo Forum - Monte Carlo Enthusiast Forums

I didn't receive an answer real quickly, so I took out to the interwebz to see if there was any possible solution out there. I didn't find much too concrete about my problem since the car had perfectly dry floorboards...that is, until the other day. I came out to the car after a long trip and looked at the floor and saw there was a good inch of standing water in the passenger side floorboard! I quickly soaked it all up, dried it out, and got online and found this TSB:

Carpet Wet on Passenger Side of Vehicle (Clean Evaporator Case Drain, If Plugged) #00-01-38-012 - (12/06/2000)

Applies to:
1999-2000 Buick Century, Regal
1999-2000 Chevrolet Monte Carlo
2000 Chevrolet Impala
1999-2000 Oldsmobile Intrigue
1999-2000 Pontiac Grand Prix

Condition:
Some customers may comment that the carpet on the front passenger side is wet.

Cause:
This may be caused by foreign material plugging the evaporator case drain.

Correction:
Inspect the evaporator case drain for plugging.

1) Raise the vehicle on a hoist.
2) Remove the rubber elbow from the evaporator case drain tube by pulling the elbow straight off.
3) Insert a 9 mm (11/32 in) drill bit, or any other similar-type instrument, into the evaporator case drain to clean out the material that is blocking the drain. (The distance to the other side of the evaporator case is 130 mm (5 in)).
4) Re-install the evaporator case drain rubber elbow. A small amount of silicone spray on the inside of the rubber tube will allow it to be slipped into place very easily. Be sure that the rubber elbow drain hole is open.
5) If the evaporator case drain was not plugged, a water leak test will need to be performed using normal water testing procedures.
6) If no external water leak was found and the vehicle returns for the same type concern, the evaporator case will have to be removed from the vehicle and the foreign material removed from the evaporator case.
Even though I have a '98, this still sounded like my problem. Unfortunately for me, I had just arrived at the in-laws house which was hours away, so I had no tools with me and no tools available to me at their house.

So, here is my DIY, with pictures. (Does this forum not support attached pictures? Don't want my links to pictures to get broken months/years on down the road.)

1) Let the engine cool completely. I let the car sit overnight before fixing this.

2) Pop the hood of your car and raise it.

3) Move to the passenger-side front fender and lean into the engine bay. You should see something like this:

[/URL]

4) Lean forward closer to the firewall, towards the middle of the car. You should see something like this:

[/URL]

5) Locate the "L" shaped boot aimed at the ground.

6) Pull it off of the firewall.

7) Watch water that was sloshing around behind the dash rush out.

[/URL]

8) Look at the L shaped boot and inspect for a clog. Mine looked like this:

[/URL]

9) Clean the end of the boot off and remove all of the grime blocking the water flow. I elected to cut a larger hole in the end of the boot with some house scissors.

10) Replace the boot back on to the firewall. Start up the car and take if for a slosh-free test drive.

Hope this helps!
 
  #2  
Old 07-16-2011, 12:15 PM
Join Date: Jul 2011
Posts: 1
Default Thank you!

I own a 1998 MC with a 3.1l motor that I have taken care of since it was a baby at 54k miles. One day, I noticed a sound coming from behind the dash of water sloshing side to side when cornering. The sound progressively got worse, getting louder and also sloshing when accelerating and decelerating. I noticed that it was only happening when I had the a/c on, so between that and the fact that my coolant level had not moved in months, I ruled out the idea that it was a plugged heater core.

I originally posted my problem here: Sound of water flowing when giving car gas. - Monte Carlo Forum - Monte Carlo Enthusiast Forums

I didn't receive an answer real quickly, so I took out to the interwebz to see if there was any possible solution out there. I didn't find much too concrete about my problem since the car had perfectly dry floorboards...that is, until the other day. I came out to the car after a long trip and looked at the floor and saw there was a good inch of standing water in the passenger side floorboard! I quickly soaked it all up, dried it out, and got online and found this TSB:



Even though I have a '98, this still sounded like my problem. Unfortunately for me, I had just arrived at the in-laws house which was hours away, so I had no tools with me and no tools available to me at their house.

So, here is my DIY, with pictures. (Does this forum not support attached pictures? Don't want my links to pictures to get broken months/years on down the road.)

1) Let the engine cool completely. I let the car sit overnight before fixing this.

2) Pop the hood of your car and raise it.

3) Move to the passenger-side front fender and lean into the engine bay. You should see something like this:

[/URL]

4) Lean forward closer to the firewall, towards the middle of the car. You should see something like this:

[/URL]

5) Locate the "L" shaped boot aimed at the ground.

6) Pull it off of the firewall.

7) Watch water that was sloshing around behind the dash rush out.

[/URL]

8) Look at the L shaped boot and inspect for a clog. Mine looked like this:

[/URL]

9) Clean the end of the boot off and remove all of the grime blocking the water flow. I elected to cut a larger hole in the end of the boot with some house scissors.

10) Replace the boot back on to the firewall. Start up the car and take if for a slosh-free test drive.

Hope this helps![/QUOTE]

THANK YOU! YOUR PICTURES AND DIRECTIONS WERE GREAT AND EASY TO FOLLOW AND SOLVED MY PROBLEM AND SAVED ME MONEY! MR. WHITE
 
  #3  
Old 07-11-2013, 05:24 PM
Join Date: Jul 2013
Posts: 1
Default ac drain plug clogged

Hey you the man dude could not figure this out my mom uses the ac alot and had water sloshing in the blower motor area. I was one day away from going to the dealer and having them figure this out and then stumbled upon your posting and saved me a ton of money. followed your pics and holy moly about a half gallon of water came out took razor blade and cut that end off now problem free thanks again you the man!
 
  #4  
Old 07-11-2013, 09:35 PM
STUMPMI's Avatar

Monte Of The Month -- February 2013
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Un-plugged my evap tube today...(With a looong screw driver)

I easily had at least a half gallon or more come pouring out...

Turns out the fresh intake (at least on a 1999)... Gets leaves,twigs, cottonwood seeds etc falls into windshield grille and works its way into the evap box... and ends up plugging the evap tube... (Theres suppose to be a screen in there to block it from falling into the system)

Thanks to your post...
My AC works much more efficiently! and the Mildew smell is Gone!
Thanks for the Post!
 
  #5  
Old 09-07-2013, 04:53 PM
Join Date: Aug 2012
Posts: 2
Default

Vandy you are a freaking rockstar in my book right now! Ironic that the original post was on my birthday, but I was about to have a mechanic look into the heater core. You saved me so much money. Thank you so much!
 
  #6  
Old 09-09-2013, 03:03 PM
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Originally Posted by Jeherr View Post
Vandy you are a freaking rockstar in my book right now! Ironic that the original post was on my birthday, but I was about to have a mechanic look into the heater core. You saved me so much money. Thank you so much!
Awesome! Glad I could help! Go spend that money saved on something that's a better investment than your car!
 
  #7  
Old 05-20-2016, 05:53 PM
Join Date: Jul 2015
Location: Long Island NY
Posts: 53
Default

Looks like the photos are long gone...
 
  #8  
Old 05-21-2016, 12:16 AM
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Unfortunately the pics were externally hosted and the member who shared this info has been away from the forum for a long time. Not sure there is any way for us to recover them.
 
  #9  
Old 05-21-2016, 12:15 PM
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Originally Posted by The_Maniac View Post
Unfortunately the pics were externally hosted and the member who shared this info has been away from the forum for a long time. Not sure there is any way for us to recover them.
Hello - still here, just don't own the Monte Carlo anymore. I tried attaching the pictures but must've been under some post limit that prevented attachments being made. If you see the original post, I asked if I could attach the photos to the post. I can try to dig up the pictures on an old hard drive.

The elbow is black, fits in the palm of your hand, and is a 90 degree bend. Yank it off the firewall, let the water behind it pour out, then clean out the end of the hose and replace. Super easy.
 
  #10  
Old 12-09-2016, 12:35 AM
Join Date: Dec 2010
Location: Brevard County, FL
Posts: 508
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If only I'd had this when my 98 GTP developed the same problem. Yeah, 98, not 99 or 2000. SS, DD.
 
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