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

asked by on October 30, 2016

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.

Clear fluid is leaking Inspection $94.99 - $114.99 Get a Quote

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.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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


Experienced Mechanic?

Earn up to $70/hr

What others are asking

What do I do if the starter turns slowly or the lights are dim?
When you turn the key in the ignition, the starter should engage quickly with no hesitation. Your interior lights should also turn on at their normal illumination. If the starter seems to be sluggish or the lights are dim, the...
Loud banging noise when I put car into gear.
I would take the car to a mechanic that specialises in transmissions. They can determine if it is in the differential or the transmission.
Broken spark plug in head
Having a broken spark plug in the cylinder head is never a good thing. If the threaded part of the plug is in the head then it needs to be extracted in one of two ways. There are special extraction...
Everytime I drive on the freeway 60+ mph it starts to wobble.
This a warranty issue and that means that, regardless of the cause, which I will help you with momentarily, the dealership is absolutely required to resolve this issue and resolve it pronto due to the existence of Federal and state...
I had a new serpentine belt and pulleys put on my car but the belt tends to keep popping off,
The serpentine belt need constant tension on the belt to keep it from coming off. If the belt alignment is not aligned then the belt may come off. The tensioner may be out of alignment and not putting enough tension...
transmission not shifting and the rpm's keep climbing up.
Hi there. It seems that the gears are slipping and causing the rpm's to climb up. Check the transmission fluid and make sure that it's full and red in color. Very dark red or black transmission fluid is an indication...
Fuel smell
This is likely related to your EVAP emissions system and something called a purge valve solenoid. The EVAP system prevents fuel vapors from the fuel tank from escaping into the atmosphere. The EVAP system collects and temporarily stores the fuel...
Neither my electronic key or car will start.
Hello, thank you for writing in. The vehicle is not getting power from the battery for one reason or another. There are several things that you can check. One being the battery cables. Make sure they are clean, dry, and...
why is my car only misfiring when I accelerate, what can be the problem?
The problem may be a fuel delivery problem like clogged injectors. Have the fuel pressure checked and filter replaced and see if this helps? Replace the plugs and wires as needed.

Related articles

How Often Does My Car Need a Radiator Flush?
A A radiator is part of the internal combustion cooling system in a vehicle. It is a form of heat exchanger, designed to transfer heat from the heated coolant mixture as it flows through the vehicle. Radiators operate by pushing...
How to Buy a Good Quality A/C Compressor
The A/C compressor helps regulate the flow of refrigerant throughout the A/C system. High quality A/C compressors are new and easy to install.
The Best Tool to Find Coolant Leaks
Diagnosing a car issue can be a tricky without proper tools. A coolant pressure tester is useful for diagnosing overheating issues and coolant leaks.