Auto Repair Help
Carl’s Corner – Auto Repair Help

By Carl O’Reilly

There is a liquid present on the floorboard of the vehicle. The fluid may be green or clear and may be more noticeable after operating the heating or air conditioning system.

Water present on the floorboard is usually caused by one of two things. Water is circulated into the passenger compartment through the heater core. The heater core is heated by the engine coolant. Air is then blown over the heater core, by the blower motor when the heater is on, to heat the passenger compartment. If this core develops a leak, it will usually leak into the passenger compartment floorboard. A heater core that has only a pin-hole sized leak, may not be leaking on the floor but may produce a fine mist or oily film that collects on the inside of the windshield. The evaporator core is also located in the same housing as the heater core. During normal air conditioning operation water will condense on the core. This water is normally drained out of the passenger compartment through a evaporator drain hose. The hose connects from the evaporator case inside the vehicle to the exterior of the vehicle at the rear of the engine compartment. If this hose becomes restricted, the water that condenses on the evaporator core will leak into the passenger compartment. This is usually clean water that will evaporate as opposed to coolant that will not evaporate and leave an oily film on the floorboard carpet.

You should verify the type of leak present. The heater core contains coolant that will feel oily and may have a green color to it. Water from the evaporator core will be clear with no color. Taking a white piece of paper and absorbing some of the fluid may help determine the fluid type.

The only corrective action for a leak in the heater core is replacement. Do not use radiator stop leak or other sealant products in an attempt to fix a leak in the heater core. If the fluid is clear, the evaporator drain tube may be restricted or plugged. This hose is usually visible at the lower rear of the engine compartment on the right (passenger) side of the vehicle. You can inspect and/or clear the blockage by passing a piece of stiff wire through the end of the hose.

A heater core that is leaking cannot be repaired and must be replaced. On most vehicles, replacing the heater core is an extensive and time-consuming project that may require special tools. The evaporator core that contains the refrigerant (Freon) for the air conditioner may be contained in the same housing as the heater core. On these vehicles, the housing is removed as a single unit and requires the refrigerant to be removed from the air conditioning system using special equipment. You should consult a repair manual specific to your vehicle or consult the advice of a professional technician prior to undertaking this job.

14 responses to “Liquid Present On Floorboard”

  1. Rich Stuhlmacher says:

    How do your remove the coolant from the carpet?

  2. Linda says:

    When it comes to emergency I came to know that we can use soaps to block any kind of small leaks temporary. Would like to know your thoughts about it. 🙂

  3. Jinger says:

    Thank You Carl for the above information. It would seem my dodge ram went from a small leak (mist) to a larger leak ( coolant on passenger floor ).
    Will I be safe adding coolant until I can get another vehicle ?
    The truck isn’t worth the heater core replacement cost ;(
    Thank You

  4. Veda Ewell says:

    These are actually the kinds of opportunities that people invariably neglect to go about doing.Simply like changing your filter inside their furnace.

  5. Heidi says:

    Well, just one more project. I am glad I decided to start fixing cars.

  6. Linda M says:

    When I turn to the right I hear like a hiss. Supposedly the heater core was replaced 6 month’so ago. Two days later it started leaking again. This time the drain hose was cleared. Started leaking again and now my passenger floorboard is sopping wet. The air/heater will run only an hour or so, then no air movement at all. You can hear the fan motor working but no air. Any ideas??

  7. Josh says:

    Ok I have a 4 cylinder 2.2l 97 camry and cannot figure out why there is a spot of either oil or sludge coming up from the floor on the passanger side. Its not constantly flowing but it has gotten bigger since I bought the car. I keep up with the tune ups regularly, I just can’t figure out how the greese is coming up into the floor on passanger side. Help!

  8. Linda says:

    My leak just appeared one morning but was on the drivers did,tanyone know what it might be?

  9. Kim eastwood says:

    Just changed the heater core but antifreeze is still going in my back passenger floorboard why

  10. Bill Matthews says:

    I spilled a cup of tea onto the driver side floor of my 2015 Ford Focus, Is there any chance this could cause damage in the floor or elsewhere?

  11. Joel says:

    I have this exact situation in our 2003 Saturn Ion. A small amount of clear liquid dripping onto passenger floormat, an occasional ‘hissing/swishing’ noise when cornering that very much sound like water moving around. I knew this was condenser condensation because the liquid is not anti-freeze. I guess I’ll be looking for the drain hose and getting this cleaned-out. Else, to the local garage and let them deal with it…

  12. Troy says:

    If there is a leak in the evaporator core would this stop the air con from working? I have clear water on the passenger side that I just discovered and about 4 days ago my air con stopped working. Also is it hard and expensive to fix?

  13. Steve says:

    Thank you, Sir! I had to disconnect the hose under the dash panel and insert a wire up into unit to dislodge whatever was impeding the water — it worked!!

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