2001 Chev Suburban and leaking heater core?

I have a significant wet spot in the carpet on passenger side under the dashboard. After removing the carpeting in that area, I inspected the floor area for possible signs of water intrusion. Does not appear to be any. So I’m assuming there is possibly a leak in the heater core or an area near there. I’ve never dove after a heater core replacement and know very little about them. Is it possible for heater cores to leak intermittently? I’ve only noticed a small drip on the floor after day one removing the carpet and haven’t seen any more since. The weather here has been dry for several days so I can’t really rule out a leak in the cab somewhere. Please share any thoughts and troubleshooting tips to help solve the mystery.
Thanks, Boomer

A plugged AC drain hose/tube can cause water to leak on the floor.



Could be the heater core. You should be able to tell if it’s coolant or just plain water by the smell, though.

The drain in the cowl may be clogged if it’s just water.

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If it is faintly sweet and slightly oily, it is coolant…that is a heater core.

If it is wet and musty smelling, more likely a clogged condensate drain. That drain is on the firewall side, towards the passenger, I think. Rubber hose looking outlet.

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If it were the heater core, the windows would be fogging up on the inside.


besides the suggestions above I will add 2 more. some owners found that the leak was coming from the seal around the windshield on the passenger side. also, if you have a sunroof the drains can be clogged or have a break in them.

Then it’s not a rain water leak.


it could be wet from before the heater core replacement. carpet takes a long time to dry, especially if the water is under the carpet.