The reason why I call it mysterious, is because I have checked under the car at all the brake lines, no leaks, checked the calipers, no leaks, I recently replaced the ABS Pump because it WAS leaking brake fluid, however, when I replaced the pump, the brake fluid was still leaking at the same rate it was before and the ABS pump I bought is NOT leaking.
The master cylinder is a possibility, but the pedal does not feel soft , nor does it ever sink to the floor.

Im not expert on brakes but I really dont know where to look next. If anyone knows where it MIGHT be leaking from please help id really appreciate it, because the fluid leaks down to halfway in the master cylinder everyday,and there are no external leaks anywhere.Im almost ready to bring my car to a dealer to have them diagnose it because I, nor anyone I know can seem to find any problems so...... PLEASE HELP! lol

 

I would recommend that you buy or borrow a Power Bleeder. That will allow you to pressurize the system to look for your leak.

 

IIRC, the master cyl can leak 2 places that are not obvious:
1. into the brake-assist vacuum chamber - the fluid is sucked into the engine thru a leaky seal - this requires a perforated vacuum diaphragm in the assist unit
2. inside the car - drips down under the carpet below the cyl

 

You missed one....

3. If a manual, then the clutch master shares the same fluid and could be leaking out of the slave and into the clutch housing. Pull the clutch inspection plate and look for wet areas or fluid dripping.

later

 

You're right - he didn't say he'd checked the clutch system for leaks.

Dave

 

However, the reservoir is mostly divided. Therefor, you can have a leak on one side and not effect the other side (i.e. the brakes having a leak and losing all its fluid won't drain the clutch, and vice versa). The clutch side of the reservoir is not so easy to see so if he's noticing the reservoir is low, then he's probably seeing the brake side.

 

Yes your right. I have not checked the slave cylinder for leaks, and my car is a 5 speed manual. From what I know, The 3rd gen RX7's use the same fluid for the brakes and the clutch. BUT, IF the slave cylinder was leaking, would I notice it leak externally? or would I have to disassemble it to see it?

 

It would leak through and drip underneath the car on the drivers side (about as far up as the side mirror ).

 

Thanks for the help!! I have found the brake leak =) My brother and I looked at the clutch system and located the clutch master cylinder and then looked in the interior of the car and there is brake fluid all over the carpet and leaking all over the floor mats. This explains why there are no external leaks. Now I know what the problem is, and its gonna be solved, thanks again!

 

There ya go.

later

 

Glad we could help!

Dave

 

I'm kinda having a same mystery. I let my brake fluid run low on purpose to see if its the clutch or brake. It goes to completely empty in the middle spot of the brake fluid container. Does that help diagnose this issue? Don't see any at the lines or inside the car nor on the ground. Is it getting sucked into the engine? What do i need to check/ fix to get it to stop?

 

You need to check the clutch and brake components for leakage. To check the clutch master cylinder, crawl under the driver seat and press the clutch pedal and look at the firewall underneath to see if anythings wet. To check the slave cylinder, remove the part, and if you see brake fluid on the outside of it, then its bad. If the brake master cylinder is bad, usually the brake pedal will sink to the floor. Same thing for the clutch pedal, if the slave or clutch master cylinder are bad, the pedal should sink to the floor... in most cases.

The key is make sure to check both the clutch AND the brake hydraulic system for leaks. Check the FSM to find all the possible places it can leak from, because that will make things easier.