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Wet Carpet Ppassenger Side.


Active member
Jul 12, 2012
1988, C4, I've have this problem with wet carpet passenger side after a good rain. Years ago I found a drain tube located far right side of the heater box behind the air grill that was blocked and after cleaning it thought I had fixed the problem. I'm still having the same problem, does anyone have any knowledge of how the rain water is routed when it enters the air intake, I found one drain tube but there must be another.
Thanks Hot Dog, Do whatever it takes to get info from someone who knows what there talking about. Actually I didn't realize it was posted twice, I thought I edited to make it less wordy.... So far the only response I've had is to drill holes in the floor.
Does it get wet just standing or do you need to be moving for it to get wet. My 90 the windshield seal leaks at the bottom and in rain the water blows under the windshield. I have tried injecting sealer from the bottom but it still leaks.On mine it usually runs down between the dash and the side panel.
Thanks Wayback, I considering buying one if I get stumped, would like to fine a cross sectional diagram of the heater core to see what I'm looking at and to see if the camera would fit around the corners.

Thanks DWinter and I had thought of that few years back and taped off anywhere the rain could get it except for the air intake on passenger side and rain got in while standing in the driveway.

Seems the rain has a straight shoot into the heater core assy from the air intake grill under the windshield wiper blade so there has to be a way for the water to escape efficiently and that's what I'm really trying to find. I'm surprised that more people haven't had similar problems like this on older c4's.

Wonder where I can find a breakdown diagram of the actual heater assy which would show how it drains.

Many thanks for your input...
Wet footwell(s) on a C4 can be caused by:
1) the forementioned plugged/restricted drain tube,
2) leaking weatherstrips
3) windshield weatherstrips
4) leaking heater core


Wonder where I can find a breakdown diagram of the actual heater assy which would show how it drains.

Many thanks for your input...

Factory Service Manual. You can get them from Corvette parts suppliers such as Zip Products.
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Thanks Hib.... I duck tapped anything to do with anywhere the water could get in. The whole door, windows, weather stripping across the top of the windshield and down the sides.

I have the original GM service manuals, one big thick one and one small one for the electronics and mentions very little about this problem. Section 1B covers "Heater & Air Conditioning" and mentions very little about the heater in general and much about the A/C.

As per my last post I mentioned that the water comes in through the air intake and there's got to be a way for it to get out .....or were going to have a wet carpet :)

My observation is that the drain hose at the far right of the heater box seams so far away from the air intake which as you know is just to the right of center. There must be a way for the water to get out closer to under the air intake. I can understand a vehicle 35 years old is going to have a layer of crap at the bottom that maybe not exited and is could be blocking something causing an overflow.

Any thoughts would be appreciated...
So, with the exception of the bottom of the windshield, you have taped-off all the possible places water could enter via failed weather seals.

That leaves plugged water drains or a leaking heater core.

I'd start with a water test. It takes two people. One person to hose down the HVAC intake and another monitoring the passenger side footwell watching for water draining in.

Check the hose that drains HVAC condensation from the evaporator to underneath the car to make sure it's clear.
Ah Ha! I mentioned in my original post that I had found a drain hose behind the outside removable air grill and that I suspected there was another but couldn't locate it. If you can explain where it is I would really appreciate it. I have ran water into the air intake area but due to probably being blocked water wasn't coming out except the floor area.
The evaporator drain is no inside the car.

It's the hose which drips water if you idle for a long period while parked with the A/C on. To be honest, I don't know exactly where it is on a C4 but you should be able to see it from beneath the firewall area if the car is on tall jackstands or on a lift.

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