Hello CarTalk community.
I have a 1991 Accord LX wagon that is leaking coolant. I figured it out b/c there is a green fluid pooled on the floor behind the passenger’s seat. Why would coolant be leaking there? I bought this car in February and have been nickled and dimed ever since. I want to sell it and get something else but I want to get the coolant problem fixed first and need to know if this is going to be expensive.
Thanks for your help!
@ZBC It is possible that your heater core is leaking. It is located underneath the dash. Leaking coolant could easily have moved back a few feet every time you drive.
The coolant behind the front passenger seat is probably from a leaking heater core. A heater core can leak coolant onto the firewall, run under the carpet and collect behind the front passenger seat.
Pull the carpet back from the firewall on the passenger side to see if coolant is running down the firewall.
Tester
Is this an expensive repair? It sounds like it would mean replacing the heater core…
Replacing the heater core may be fairly expensive. Not so much that the heater core itself is super-expensive, but that sometimes this job can be very time consuming for the tech, and they charge labor by the hour. Before you do that, you should probably take your car to your local radiator shop and ask them to test the heater core while it remains in the car. They have ways to pressure test in-car heater cores. And they have experience with this problem too, so they might be able to determine the heater core itself isn’t leaking, just a hose has cracked or come undone.
Since it is summer, and you don’t need the heating function for a while, you could ask someone to temporatily clamp off the input hose to the heater at the firewall too. At least it would stop the leak.
I’m assuming you purchased this car used. If it turns out the heater core actually is leaking, this would be unusual even for a 91 Accord, provided the cooling system had been maintained during the prior years as recommended in the owner’s manual. I have two cars, one 20 years old, and the other 40 years old, and both have their original heater cores and both heaters work like new. So if the heater core is leaking, well, that may not bode well for the rest of the car’s cooling system. Just a heads up.
Also, be sure to check the coolant level (in the radiator, not just the plastic jug) frequently until this issue is addressed.
Thank you, GeorgeSanJose. I drove the car yesterday and the mete for measuring H/C showed me in the red. The car shook and beeped for about 5 minutes when I took the key out of the ignition and there was smoke coming out of the glove box. 
So, a mechanic has offered to look at it and diagnose w/o charging me but I am afraid to drive it. Should I have it towed to the mechanic? Also, I do suspect that the problem is a tube somewhere b/c I also saw freeon under the hood, not just behind the passenger’s seat…