Moisture on the underside of the Floor Mats?

[bobmanx]

Is there anyone out there in the mid-year Corvette world that has any ideas as to where the moisture is coming from on the underside of the front floor mats? The carpets are dry to the touch and moisture doesnt show when placing "Service Station Type" paper towels on the carpet in both of the front foot areas, but the other day after running the 67 Convertible with the top down about 50 miles round trip with the A/C OFF, there was moisture droplets on the underside of the vinyl floor mats.

The top was down and the weather was in the 90+ range. The radiator hoses are new and the level did not drop in the expansion tank after cooling off. There was not any visual moisture lines under the defroster box area and the moisture was under both of the front vinyl mats. Car has been garaged for several years in Arizona so I'm sure that it hasnt been in the rain. and I havent washed it, so there shouldnt be any cowl drain tubes that have plugged up and allowed water into the front vents.

So I'm open to suggestions or ideas on where to look. To rule out the defroster/heater coil, what is the best way to by-pass it? plug the lines at the firewall or connect the in and out together to allow the coolant to still recirculate thru the hoses minus the heater coil?

Could it be condensation, the day was rather humid and the exhaust pipes are near the center of the car as it is a rear exhaust.

Anyone been here before and what did they find?

Thanks for all of the previous answers and help on trying to straighten out the kinks and bugs. Since the car is original, and not wanting to ruin anything, its sitting in the garage awaiting a solution or things to check.

Bob

 

[JohnZ]

Bob - That's a new one on me - maybe aliens? (sorry, couldn't resist). If you felt moisture on both sides, doubt if it's the heater core (unless the moisture smells sweet), and you sure aren't going to have any condensation in 90-degree temps. I dunno - can't wait for the real answer. Fire it up at night, turn on the heater, pull the defroster knob, and if the inside of the windshield fogs above the defroster outlet and the air coming out smells sweet, that's anti-freeze. If no fog and no sweet smell, the heater core is dry.

 

[bobmanx]

JohnZ, Aliens wasn't my first guess. lol I will try the defroster idea. I didnt think of that one. I cant remember any sweet smell while on the drive. I did have the fan switch turned on, without the heat. A long time ago I had a Datsun 510 that was all tricked out with BRE race components and blew the heater/defroster unit solder joint and no one would or could get a breath till it was cleaned and bypassed. (found a new one thru Nissan) but thats another fun story. Looks like the similar green coolant in the expansion tank.

I also dont remember any water crossings or puddles that would come close to getting more than the tread of the tires slightly wet. (Summer here in SoCal) I also did not see anything dripping out of any heater vents, and the carpet was dry to the touch. So maybe it was a alien trick. LOL

What is the recommended way to bypass the heater/defroster core without causing any other damage till a replacement can be found and checked. The heater lines in the engine compartment also connect to the expansion tank, so I'm assuming that it should remain but just route the hoses together rather than plug both and not allow coolant to recirculate thru the lines. Have you ever tried to bypass a heater core to get running again or home? "Sounds like a pain in the dash" to get the core out and replaced, sort of like the car was built around it. LOL Its a 327/350 hp with air and 4spd.

Thanks, Bob

 

[Copdogcorvettes]

Well I have had the same thing. While I had the carpet removed and everthing else I found it. The water was coming down the inside the firewall. It travelled down to the carpet pad. There was never a drip. Anyway it was coming from the wiper well; You know that area between the windshield and the firewall. When ever you wash the car or it rains the water runs into this area and then to the sides to drain. If there is anything in that area that is not seal or if there is a crack the water will leak into the inside and down to the floorboards. It then collects in the carpet pad. You will never find anything dripping.
To test this , pull your carpet back. Dry everything out, paying attention to the firewall area. Then take a hose let it run down across the windshield. Let run enough to make like a rain or car washing. Then watch the inside. That how I found this problem in mine. I though I'd never find the *@*@### leak.

Hope this helps. It may not be your problem, but it is what I found.

 

[bobmanx]

Thanks Copdogcorvettes, I will also try that test and see what happens, I will also check the drains that are in the wiper/cowl vents and make sure that they are not plugged. If its not the heater/defroster core or plugged drains or cracks in the cowl vents, maybe it is aliens. lol

Thanks for the info.
Bob

 

[Subfixer]

I have a similar problem and have found my leak to be at the windshield gasket. You may want to check that area closely. After 39 years, mine had finally dried out and cracked along the bottom edge, allowing water to enter and travel down the inside of the firewall.

 

[vettefinderjim]

I like allians, yes it must be allians !!

John gave all the correct answers as usual. The only other item Bob, is the humidity we have had here in So Cal the past few weeks with the Mexican monsune season. Just might be moisture condensenation under the large mats, especially if the car is stored near the beach. You live in Ventura as I remember, and the car is in Orange County. Maybe the roof leaks on your storage garage.

All the leaky gaskets suggestions are very valid as well, but if you don't wash it........and it is not in rainy Washington, it has to be alians !!

If the heater core is leaking, you will smell the sweet and feel the oily carpet. Check the carpet at the top of the firewall on the passanger side. I have never seen a heater core leak on the driver side. Easy to by pass , just look at how it goes in and comes out on the firewall side. Just re route the hose from the water pump nipple directly to the other intake nipple. Now comes the fun, remove the glove box, the heater box, the AC ducts and slowly the layers of plastic will reveal the heater core. It has to come out FROM INSIDE the car. You will learn how to lay on your back, get dirt in your eyes, swear, cuss, drink to many beers with to many breaks. While you are at it you might as well clean the cables and relube with white lithum grease and readjust all the controls to open and close as originaly designed 36 years ago. And then , you may even replace the worn cable bezels with nice new ons that say HEAT.......AIR.......VENT ..etc. But while doing that you realize, these are pretty, but not 100% correct as my originals, so where do I start and stop this restoration. I spent the better part of a Saturday doing the task and that was on my AC coupe small block when the motor was out, so underhood access was a lot easier. READ the SERVICE manual big book before you tackle the job unless you are ASC certified.

Maybe I should just remove the plastic mats..........pray to the moisture gods, and take the car for another drive. Now that the carpet is completly dry, I do not have to worry anymore. The allians fixed it !!

 

[bobmanx]

JohnZ, Copdogcorvette, Subfixer, and Vettefinderjim, Thanks for the suggestions. (even the aliens idea)! There isn't or wasn't a sweet smell from the green alienfreeze, nothing dripping out of the vents (heater/AC), nothing on under the dash of the inside of the firewall. Nothing on the garage floor. and the carpet is dry in both the foot wells.

I will pull up the carpet the next time that I get down there and investigate further for alienfreeze tracks. At the time I did not have the time to do any closer inspections when I parked it. Yes the garage has a new roof and the top is up on the convertible, with the windows up and locked. so if they are in there, they are stuck! LOL

If I re-route the hoses, I will have to do it after the radiator expansion tank, as its in the loop with a "tee" fitting. Before I start carefully removing the passenger side interior, I will make sure that its part of the problem, with the JohnZ test, and get a supplier for the core to minimize the down time.

Waiting for the 67 assembly manual to arrive prior to grabbing the tools. Thanks for the warning Jim as to access. sounds like a job that I will only want to do once and do it right the first time. A friend suggested removing the seat to improe the lay on your back and hate life period of the job. LOL

I know that you are all waiting for the results as to the cause, and I hope to find it before I have to disassemble the whole car. LOL Come to think of it, aliens isnt such a reach to believe!!

Thanks Bob