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GM A/C Condensate Drain Unclogging & Cleaning Guide
How to fix a water leak on the passenger floorboard due to a clogged GM HVAC condensation rubber elbow drain.

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Paul B. Michaels
Author & Photographer
Auto Mechanic Since 1989

This automotive how-to guide was specifically written to assist owners of the 6th generation (1997, 1998, 1999, 2000, 2001, 2002 and 2003) GM Pontiac Grand Prix in unclogging and cleaning the air conditioner's rubber elbow drain pipe which can cause a water leak on the passenger side floorboard.

The procedure should be the same on other General Motors vehicles especially those equipped with the GM 3800 Series II 3.8L V6 engine such as the Bonneville, Oldsmobile Eighty-Eight, Chevrolet Impala, Monte Carlo, Buick Regal, Riviera, Park Avenue, Le Sabre, Chevy Camaro, Lumina, Pontiac Firebird, Olds Regency, and Holden Commodore.

GM 3800 Series II Engine
Firewall, Alternator, STB
Fan Cooling Off Engine
After a long drive through South Florida on a hot summer day with the A/C blasting on "Max", my passenger noticed some water by their feet on the passenger floorboard.

I did some reading and found that this is a common problem for owners of the Pontiac Grand Prix and other GM vehicles.

Often the problem can be resolved easily by removing the rubber elbow tube attached to the end of the HVAC system's condensate drain pipe and cleaning out any obstructions.

Before I got around to doing that, I parked my car in the garage and used a wet/dry shop vacuum to suck up most of the water.

To get all of the water out and prevent mold from growing, I had to remove some of the plastic trim pieces and peel up the passenger side carpet.


Remove Buick STB
Wire Pointing To Elbow
Condensate Drain Pipe
The A/C condensation water drain pipe (or "tube") and rubber elbow cap are located in the engine bay on the firewall closer to the passenger side of the vehicle.

In the pictures above, you'll see me pointing to the rubber elbow with a white metal clothes hanger that I straightened out.

The elbow is just past the alternator and power steering reservoir on the lower middle section of the firewall when you're standing at the passenger side of the car.

Rubber Elbow On Firewall
A/C Drain Elbow Removed
Firewall Side of Elbow
I was able to reach the rubber elbow without removing any parts just by reaching in diagonally between the two hoses located below the alternator.

(Later, I figured out that removing the coolant overflow tank made it a lot easier to reach the rubber elbow.)

I pulled off the rubber elbow and saw some water leak down onto the garage floor.

The restricted end of the elbow was partially clogged with some brown mold/fungus/sludge and debris.

I thoroughly cleaned out the elbow and used a pair of scissors to cut open the restricted end to hopefully avoid a clog in the future.


Restricted Drain Opening
Wire Hanger Bent Over
Remove Coolant Tank
To ensure that there wasn't anything else clogging up the A/C condensate drain pipe further up the line, I used a straightened wire clothes hanger to snake out the pipe.

You can also use a long plastic zip tie or "cable tie". Again, I found that removing the coolant overflow tank made it a lot easier to access the drain pipe.

I didn't have the time for it, but I later thought that sucking out any debris from the end of the condensate drain pipe with a wet/dry shop vacuum would have been a good idea.

When you're done, just pop the rubber elbow back on the end of the drain pipe and face it downwards to allow water to easily escape.

Coolant Tank Removed
Snaking Out Drain Pipe
Rubber Elbow Cut Open
For more of my related automotive how-to guides, click on the following links: GM Power Window Motor & Regulator Replacement Guide, GM Power Window Tracks & Regulator Lubrication Guide, GM Pontiac Grand Prix Headlight Bulbs Replacement Guides, GM Pontiac Grand Prix Tail Light Bulbs Replacement Guide, Zaino Bros Show Car Polish Review, WeatherTech FloorLiner Car Mats Review, GM 3800 II Power Steering Whine Repair Guide, GM Pontiac Grand Prix Front Brake Pads Replacement Guide, GM Brake Line Bleeding Guide, GM Pontiac Grand Prix Rear Brake Pads Replacement Guide, Headlight & Tail Light Condensation Solution Guide, GM Pontiac Grand Prix GTP Supercharger Belt Replacement Guide, GM Pontiac Grand Prix Serpentine Belt Replacement Guide, GM 3800 II Idler & Tensioner Pulleys Replacement Guide, Corroded Car Battery Terminal Replacement Guide, GM 3800 II Alternator Replacement Guide, GM Pontiac Grand Prix PCV Valve Replacement Guide, GM ABS/TCS/SES Warning Lights Solution Guide, GM Wheel Bearing Hub Replacement Guide, GM 3800 Series II Engine Oil Change Guide, GM Power Window Switch Contacts Cleaning Guide, GM Grand Prix Fog Light Bulbs Replacement Guide, GM Key Fob Remote Control Battery Replacement Guide, Buffing Old Faded Headlights Guide, K&N Air Filter Cleaning Guide, GM 3800 Series II Eaton M90 Supercharger Oil Change Guide, GM Pontiac Grand Prix 3rd Brake Light Bulb Replacement Guide, and Meguiar's Headlight Restoration Kit Review.

For more, check out all of my Pontiac Grand Prix DIY Repair & Maintenance Guides.

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