BIG leak

[jscott]

Went to a car show yesterday (although I do not like car shows I needed to get out) which lasted 2 hours before heavy rain came in.   I have only washed my car twice in the 1 1/2 years I have had it, know I had a small leak but never looked into it, was saving that for a winter tear down.    So when I got home after driving in a really bad downpour I check the passenger front floor and found the carpet quite wet.  Peeling it back I found a puddle of water under the carpet, soaking the original cardboard type padding underneath.  I ripped that out and put a hair dryer in the area for a while to dry everything out.

Today I took out the seats and carpet, the wet area (now dry) was confined to the passenger floor board.  When I did the interior after I first got the car in about March 2020 I put sound deadener throughout the car but never forward of the front seats as I ran out and the original stuff looked good.   There was ZERO rust in/on any of the floor under and behind the seats.

The leak in the passenger side has yielded just minor surface rust and a pit or two here and there so either it has not lasted a long time or the car was not in the rain very much.  In the past I suspected it came from the open area you see in the second picture (the what looks like bunch of rust  on the left side of the pic is some original welting or what ever you call it still attached, Many wires from prior owner, I have to check and see if they are still active.  When I get a chance I will run some water over the cowl area and so forth to try to see where it is getting in.  I also noticed 4 screw holes in the side of the transmission tunnel.  I cannot imagine much water could have come thought those, I will seal them up. 

Any suggestions on where to look for this leak?  Are these cars prone to leaking at  certain spot?

I also had water in the trunk but that is another search and repair after I do the other.

3rd and 4th pics are my driver side, that rust colored area is just that, rust color.  Could have come from the build sheet which died there, you can see the last remnants of it in the last pic.

I have already ordered more sound deadener to finish the floor now that I have it apart.

On a positive note I was so happy with how well the car is running, that is what I need to do, drive a car show, park in the regular lot, walk around for an hour and drive home.  It is really about driving for me instead of showing. 

 

[71Rustang]

Also take out the glove box and maybe even the heater box if you suspect the cowl is leaking to check........

 

[Bentworker]

Probably the cowl.  +1 on pulling out the glove box liner and taking a better look.

 

[Kilgon]

Pull the grilles from the top of the cowl and stand on the driver side and shine a flash light toward the passenger side.  You might see that the cowl is rusted out above the heater box.  Also, you can put a trouble light in the cowl and then see if you see any light from the inside.  

 

[72MustangSprint]

I’m betting it’s the cowl , hopefully minor.

 

[71coop]

I've never been able to verify this for certain, but I believe there should be a seal between the diver-side wiper post and the upper cowl. I never had the seal on my car. On my heater-only car, this lack of a seal allows water to spill straight down into the "hat" that feeds the driver side vents.

I pulled my wiper transmission arms, used the right stuff to create a gasket to seal the  wiper post openings, and no more annoying water dripping on my left foot in the rain. Just one more thing to check.

 

[jscott]

hopefully I have found the leak.  It is about 2" above the arrow on the white tape.  I poured in 1/2 gallon of water into the cowl area and had a little come down from there.  That is the area I suspected it was by the way the water was on the carpet.  I can see a little black stuff goo that had been applied by a prior owner in the past.  I will do my best to seal it without taking apart any more of the car.  I did try the light thru the cowl area but the hole is so small (by the way the water dripped in) that no light was visible to me.   

 

[Carolina_Mountain_Mustangs]

You have rust around the opening in the cowl for the heater box. You can pull the heater box and probably do some temporary fix with some epoxy.

 

[jscott]

You have rust around the opening in the cowl for the heater box. 

no doubt at the rust.  I filled it the best I can with flex paste as probably over the winder I will be doing work on the dash and have more access.  Water test in a few days to see if it is sealed.

 

[Cjmach1]

Went to a car show yesterday (although I do not like car shows I needed to get out) which lasted 2 hours before heavy rain came in. I have only washed my car twice in the 1 1/2 years I have had it, know I had a small leak but never looked into it, was saving that for a winter tear down. So when I got home after driving in a really bad downpour I check the passenger front floor and found the carpet quite wet. Peeling it back I found a puddle of water under the carpet, soaking the original cardboard type padding underneath. I ripped that out and put a hair dryer in the area for a while to dry everything out.

Today I took out the seats and carpet, the wet area (now dry) was confined to the passenger floor board. When I did the interior after I first got the car in about March 2020 I put sound deadener throughout the car but never forward of the front seats as I ran out and the original stuff looked good. There was ZERO rust in/on any of the floor under and behind the seats.

The leak in the passenger side has yielded just minor surface rust and a pit or two here and there so either it has not lasted a long time or the car was not in the rain very much. In the past I suspected it came from the open area you see in the second picture (the what looks like bunch of rust on the left side of the pic is some original welting or what ever you call it still attached, Many wires from prior owner, I have to check and see if they are still active. When I get a chance I will run some water over the cowl area and so forth to try to see where it is getting in. I also noticed 4 screw holes in the side of the transmission tunnel. I cannot imagine much water could have come thought those, I will seal them up.

Any suggestions on where to look for this leak? Are these cars prone to leaking at certain spot?

I also had water in the trunk but that is another search and repair after I do the other.

3rd and 4th pics are my driver side, that rust colored area is just that, rust color. Could have come from the build sheet which died there, you can see the last remnants of it in the last pic.

I have already ordered more sound deadener to finish the floor now that I have it apart.

On a positive note I was so happy with how well the car is running, that is what I need to do, drive a car show, park in the regular lot, walk around for an hour and drive home. It is really about driving for me instead of showing.

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It’s usually the cowls they are usually rusted around the lip. So instead of water going around the raised lip it goes into the cowl and on your floor

 

[Retired2014]

Been there…
If you remove the passenger side honeycomb grille at the base of the windshield and peer inside, you can see the air intake for your HVAC box. You may be able to see rust deposits there that will foretell the cowl vent leak. Alternatively, and a little more involved, you can drop the air box down from under the dash (virtually guaranteeing crap getting in your eyes as you lie on your back looking up) and visualize the mating point of your airbox/plenum to the underside of the cowl and look for rust holes. Also check the drain hose from the bottom of the airbox and verify it exits the floor hole, not into the vehicle floor. This tends to be a real PIA-type project.

 

[1973 Mach-1]

Looking at your pictures, I see the ORIGINAL BUILD SHEET is there on the driver side floor! Please remove that as carefully as you can, and save it! (it's like gold)

 

[Stanglover]

For whatever reason, I missed this post last year.
Every time I see others with issues like this, I realize more and more how fortunate I was to find a near pristine car back in 08.
There are drain channels from the cowl to under the fenders and I'm pretty sure you'll find them blocked and the reason why the water leaked into your footwell. You'll have to pull the fender to get to them to make sure they're clear. What a figgin pain!!!
EDIT: let me say "you MIGHT have to pull the fenders". Possibly could be reached from underneath or through the cowl.