The heel pad of my carpet has worn through and my left heel get soaked in some kind of greasy fluid. It's also occurring a little on the right side where it's just separating.
Firewall is dry so it's not brake fluid, so is the heater core area so it's not coolant.
I pulled up the carpet and couldn't see anything else damp on the underside so I think some sort of glue is deteriorating under the vinyl section.
No matter how much I dab with a paper towel it doesn't come up dry.

Other than putting in whole new carpet is there anything I can patch this with? I don't think any tape will stick to it.
For now I'm covering it with a floor mat but its thickness messes up my coordination with the pedals, plus I'll have to remove it for track days.

 

Check the fluid level in your clutch master cylinder. The clutch master can leak around the piston seal and fluid can run back into the car. Typically it will just run down the firewall but maybe the fluid is traveling down the adjustment rod and dripping down onto the carpet pad. Worth a look either way.

 

also possible that the speedo drive seal has gone so it will wick gear oil up the cable and then it'll leak out of the speedometer.

 

Clutch fluid hasn't dropped, been keeping an eye on that and the brake master before and during yesterday's track day.

I also thought it might have been water intrusion from a leak in the windshield or seam sealer in the body, but like I said there's nothing else on the underside and that spot doesn't get dry.

 

Interesting idea. I tried feeling around the back of the gauges and everything is dry, though if it is dripping I should see it on the floor mat I placed soon enough.

I remember this happened on a CarTalk episode where a guy called in to say his car was bleeding on his foot and this turned out to be the cause.

 

Pu a stack of newspapers in that area and see which direction the substance wicks/drops.

 

Floormat was put down on Sunday, drove it around that day and Monday. No fluid on top, but some on the underside.
The car is parked on an incline toward the front, and some goop has puddled at the rear of the heelpad, just laying a paper towel on it and some black tinted stuff is absorbed.
Since there's nothing on the underside of the carpet, I still think something in the heelpad is disintegrating like glue or the vinyl or a combination of those with the carpet inside.

Looks I'm springing for a carpet kit. Is Auto Custom Carpets the only option for new?

 

I had a leaky heater valve back in the day. I feel like you'd probably smell coolant but I also think that liquid is coming coming from somewhere. I'd hate to see you put on a new carpet and then that gets soaked.

 

I think all the resellers get their carpet kits from ACC. https://www.accmats.com/commerce/1985/Mazda/RX-7/

 

Sure looks like hydraulic fluid. And if that is on the underside of the carpet it would be hard to dry out.

 

It's possible at some point clutch fluid may have leaked down under the carper from previous owner, or clutch master maintenance undetected and "pooled-up" at the lowest point, the heel pad area. Overtime it's begun to react with the vinyl footpad and has stated to degrade the vinyl and melt it. Just a thought.

 

Doesn't smell like coolant and the area around the heater is dry. Been there with the heater valve, face against the pedals and only enough room for one arm to work.

Firewall and rods going to the master cylinders are dry. Plus the car just had track time last weekend and the fluids didn't go down.
Both master cylinders have been replaced at some point, but I don't think any fluid has every spilled inside.
Maybe last summer's record heat killed the vinyl or something. Like how old rubber starts oozing on its own.

I figured. Oddly the best price I've found is at RockAuto.

 

When you pulled up the carpet, is the area underneath the heel pad area also covered with carpet?
If you plan to buy a new carpet, then you can cut some of the padding out with a blade to see what it looks like underneath and if the vinyl is the cause of the leak.
If you're not, put the mat over it and just drive knowing that nothing is leaking so all is good!

 

I pulled up the carpet and couldn't see anything on the underside.
New carpet set is on order and I plan on cutting the old one up to see the extent of the goop.

 

so, I'm dumb. Turns out it was in fact coolant. There's a drip on the hose that connects the heater valve to the exterior pipe.
Either my fix from several years ago wore out or the pipe itself is busted.
Looks like it had been collecting in the driver footwell but dried out along the tunnel which is why I didn't feel it there. Only the boxed in area under the heater box was damp.

The cheesy wingnut clamps were used because I could only reach one arm in there.
I used 5/8" hose back then it was a real pain getting it installed, so I'm ordering the correct 17mm hose.

 

I wonder if that new style heater hose heat shrink would work in place of those clamps? It does take a heat gun to shrink it so it might be hard to make it work. Just throwing out ideas.

 

Post #8 covered it.

At one point, the heater core feed has a hose under there that sprung a leak and anytime I'd step on the gas, Water Pump pressure would go up, and hot coolant would squirt out on my right foot. Hot enough to make you pull your foot away to avoid getting burned. That'll make you a lot slower driver, believe me.

 

Look at it this way, at least you got new carpet in the car! lol

 

Got new hoses in, will check for leaks later.
Got 17mm and 18mm hoses from Belmetric.com. The 17 fit well but looked too flimsy while the 18 fit ok and looked like common coolant hose with an internal braid so I used that.
Like I said above, back then I used those wingnut clamps because there's barely room for one hand plus a ratchet to rotate. Enter the Tite-Reach!
A Datsun buddy told me about this years ago. I got the cheap one and it made short work of tightening the furthest inside clamp.

Also the heater valve needs to be installed with the hoses fitted on the core and external pipes first.
I thought I could put spring clamps on the valve to prevent having to re-tighten later, but it just wouldn't go on that way.



More background on the original problem:
The heater valve to core and piping connections are so short Mazda used a single clamp on the hoses. That worked until the hose aged out on me ~10 years ago at which point I tried fixing with 5/8" hose.
I also found a photo from an ancient thread showing the connections with the dash removed.

 

I wonder if PEX-A (F1960) would work? PEX-A is the type that expands so it is constantly under pressure and doesn't use a clamp.

 

Maybe if it's more stretchy than rubber or comes in metric because that 5/8" was a real bear to install. Also I'm not sure it can handle automotive temperatures.

 

It's only good to 200°F. -> 80 psi at 200°F

 

Finally have no leaks.
The hose at the firewall was no trouble but the heater valve to core hose was troublesome because I didn't know it was leaking until coolant started dripping out of the heater box.
It would have ruined my day if I overtightened and deformed the heater core inlet but new hose requires some breaking in.
Also I got the clamps that have another band inside so the screw perforations don't eat into the hose.
Put down paper towels to see if anything drips overnight, if it's clean then the new carpet can go in.

 

Glad you were able to get it fixed. That hose does indeed look short and I can imagine the difficulty installing it with parts in the way!