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· 2003 Xtreme
54 Posts
Source: GM TechLink

Water Leak in Front Floor Carpet Area
Affects 1998-2003 Chevrolet S-10 and
Blazer, 1998-2001 Oldsmobile Bravada,
1998-2003 GMC Sonoma, 1998-2001
GMC Jimmy (US), 1998-2003 GMC
Jimmy (Canada Only), 1998-2001 GMC

Some of the above vehicles may have a mildew odor or wet carpet in the front passenger seat area. Here are the most common causes and cures.

- Water backing up at the plenum drain

Too much sealer at the plenum drain area can act as a dam, allowing water to back up in the plenum and either seep around the air box seal or around the lower right air box mounting screw. If a plenum drain has a ridge of sealer higher than 1/4 inch (6.4 mm), use a utility knife to cut the sealer down to 1/4 inch (6.4mm) in height.

- Voids in the plenum seam sealer

Use a mirror to examine the inside of the plenum for possible voids in the seam sealer where water can gain entry to the passenger compartment. Seal any voids using the procedures listed in the service manual.

- HVAC recirculation door being left open

The HVAC recirculation, or air box, door opens upward when the HVAC controls are set to MAX A/C. In extreme conditions, water can pool on top of this door and spill into the vehicle. This door can remain open if the HVAC mode is set to MAX A/C when the ignition key is cycled off. Customers should be informed of this condition and should be advised to turn the HVAC setting to the regular A/C or OFF position before turning the vehicle off.

TIP: Water may still leak into the passenger compartment, even with the recirculation door in the fresh air position. This may occur in extreme conditions (heavy downpours, etc.). Check for a hole above the air box (between the two threaded holes that retain the right front fender) for proper sealing. This hole should be sealed if found not to be sealed properly. To prevent water leaking into the passenger compartment(s), even under heavy downpour conditions, fabricate a small plastic dam, 3/4 inch (19 mm) high x 3 inches (76 mm) long, then glue and seal it to the recirculation register under the recirculation door. This will allow small amounts of water (1/4 inch (6.4mm) to 1/2 inch (12.7 mm) to puddle in the HVAC case without entry into the vehicle.

- Door harness boot

Water that is found in either the driver or passenger floor at the A-pillar may have entered at the door harness boot on the A-pillar side. Make sure the boot harness if fully seated in the A-pillar.

- Plenum/Cowl/Instrument sub panel (windshield tray)

Water may enter at the three piece Plenum/Cowl/Instrument sub panel. This area must be sealed from the inside of the vehicle; the dash assembly must be removed to gain access. This area can be sealed by spraying a clear sealer (KENT brand) in a gallon commercial sprayer, up under the Plenum/Cowl/Instrument sub panel.

IMPORTANT: Please follow these diagnosis processes thoroughly and complete each step. If the condition exhibited is resolved without completing each step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicles listed and should not automatically be used for other vehicles with similar symptoms.

- Thanks to GM Technical Assistance
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