Diagnose and fix water on floor passenger side
A damp carpet or water on floor passenger side situation can be caused by a plugged AC condensate drain line, a leaking heater core, leaking windshield seal, a problem with sunroof drains or water ingestion from the fresh air intake on your car’s HVAC system.
Water on floor passenger side from clogged AC condensate drain
This is one of the more common problems. It’s caused by bacteria buildup on the AC evaporator coil located in the heater box under your dash. Bacteria from airflow combines with condensation from the AC coil to produce a mildew/mold smell and the formation of a slime on the AC fins. In addition to normal bacteria, organic material can also be sucked into the HVAC system and land on the AC evaporator fins. The organic material then decomposes, making the smell and slime situation even worse.
At some point, all the slime and organic material plug the drain line. The drain line is a rubber hose that runs from the heater box, through the floor and then to the underside of the vehicle. When it plugs, condensation water builds up inside the heater box until it reaches a seam. The water then drips out of the heater box and onto the floor of your vehicle, most often on the passenger side.
Fix a clogged AC drain line
There are two ways to clean an AC drain line. The easiest
and least messy way is to locate the drain line from under the vehicle and insert a flexible item line a pipe cleaner or speedometer cable into the drain line to dislodge the clog. This will require you to jack up the vehicle and place it on jack stands. Poke the opening until the water flows freely. Then buy a can of KOOL-IT Evaporator and Heater foam cleaner to remove the bacterial buildup and treat the AC coil to delay the onset of slime.
If you can’t find or reach the drain line from under the vehicle, you can clean the line from inside. Gather lots of old towels to catch the flow of water the instant you disconnect the drain line from the heater box.
- Remove floor mats on passenger side
2) Locate the rubber drain line running from the heater box to the floor.
3) Loosen the rubber drain line from the heater box by rotating it to break the temporary rubber to plastic bond. Then slowly remove it and slide a towel under the plastic nipple to catch the drain water.
4) Once the water has drained, clean the drain line using a pipe cleaner or speedometer cable. Use compressed air to blow all debris from the line.
5) Then buy a can of KOOL-IT Evaporator and Heater
foam cleaner to remove the bacterial buildup and treat the AC coil to delay the onset of slime.
Water on floor passenger side from leaking heater core
The heater core is a small radiator located in the heater box under the dash. Hot engine coolant circulates through the heater core to provide heat to the cabin. When an owner neglects routine maintenance by going beyond the recommended intervals for coolant changes, the coolant loses its ability to prevent corrosion. When a heater core deteriorates due to corrosion, it develops pinhole leaks that allow engine coolant to drain out inside the cabin. Often the coolant drains out the same line as the AC condensation. But in some vehicles, the heater core isn’t located near the drain line. In those applications, the leaking coolant builds up and drain out a heater box seam and onto the floor. The ONLY fix for a leaking heater core is replacement. Cooling system sealants generally don’t work and even if they do, they’re not a permanent fix.
Water on floor passenger side from leaking sunroof drains
All sunroofs leak water. Car makers know this and add roof drains to every sunroof. There are usually two drains in the front, one in each corner and at least one drain in the rear. The front drains route through the left and right A pillars to spill water onto the ground. Leaves can clog these drains and cause water to leak onto the floor passenger side and driver side. If you only notice water on floor passenger side or driver side AFTER washing your vehicle or after a rainstorm, suspect a plugged sunroof drain.
Water on floor passenger side from leaking windshield seal
A damaged windshield seal can allow water to seep into the cowling and down the inside of the firewall. If you notice water on floor passenger side or driver side AFTER washing your vehicle or after a rainstorm, and your roof drains are clean and draining properly, suspect a damaged windshield seal. Take the vehicle to an auto glass repair company to fix the leaking seal.
Water on floor passenger side from HVAC fresh air intake
Some car makers locate their cabin air filters in the cowling or located their fresh air intake near the windshield drain off area. In those applications, water can enter the vehicle from the fresh air intake. If water enters your vehicle when raining with the HVAC system set to fresh air, suspect a problem with the fresh air intake.
Check car manufacturer technical service bulletins before trying any repair. Many car makers have come out with deflector shields to prevent fresh air intake water intrusions.
©, 2018 Rick Muscoplat
Posted on by Rick Muscoplat