Q: Water leak on the passenger floorboard w/defroster and AC running.

asked by on

When running defroster on max hot settings (outside air and AC on), there is a high pressure noise followed by clear water leaking into the passenger floor board. It does this after 30 minutes of driving with defrost, and usually immediately stopping at an upward incline coming off the freeway. In a heavy rain climate.

the water is clear and odorless. Heater produces hot air and defroster works with AC on. The coolant temperature gauge is always cold regardless of driving conditions.

I originally thought it was an heater core issue but there is no sweet smell, and the vehicle produces hot air. I was thinking it could be the AC system issue. The AC system produces poor cold air in summer, and there does not seem to be a clogged drain hose.

There does not seem to be any coolant loss. I was quoted $1200 to $1600 to take the dash apart just to diagnose heater core, but Im not sure it's even the issue.

My car has 140000 miles.
My car has a manual transmission.

If the leak does not contain any antifreeze or other "engine coolant" AND the leak is not due to A/C condensate backing up (if the A/C is working, just check for flow of condensate onto the ground or if this issue is occurring when the A/C is not even in use, the possibility of condensate being the source is moot, of course), then the only other possibility is a rainwater leak which leak is contained and "invisible" until you force the water out due to the operation of the blower.

If it is rainwater incursion, they may be no need to take the dash apart, rather the leak has to be sought outside the vehicle perhaps around the cowl and/or the windshield. The key though is to be sure it is not coolant and it is not condensate. If it is neither of those, it must be rainwater unless you have installed plumbing in your car. If you want to have this looked at by a different technician, a qualified professional from YourMechanic can come to your car’s location to diagnose the leak at a lower rate.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. Water leak on the passenger floorboard w/defroster and AC running.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Coolant leaking, engine might be messed up now

You are correct in not wanting to start the car to avoid any further damage. It sounds like you might have coolant leaking into one of the cylinders due to an engine block failure, resulting in a misfire. What needs...

Q: During spirited driving, power cuts out on hard left turns

Hello. The symptoms you are experiencing can commonly be caused by a weak fuel pump, or a fuel pump strainer. If the fuel pump is the original it may have weakened over time, and has become unable to provide the...

Q: What does the Cruise Main indicator light mean?

The Cruise Main indicator light is located on the instrument panel. When you press the Cruise button to turn on the cruise control, then the Cruise Main indicator light will illuminate.

Related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.