No wonder Ford is going broke ,took mine in they replaced the whole master cylinder, still leaks so they spent money for nothing, and all they have to do is find a gasket that works for about .25 cents.

 

Who can we contact at Ford engineering to get this dumb problem fixed?

It needs one of 2 things:

* new reservoir with a float that comes all the way to the top (possible solution)

* thicker cap gasket to prevent seepage (definitely a solution)


Git'R'DONE!

 

i took some plumbers tape (stuff used for threads to prevent water leaks) and wrapped it around the threads a few times and stuck the cap back on.

no more leaks.

 

Delete

 

How much teflon tape did you use? I used maybe 2-3 wrappings and although it didn't feel thick, it awaits to be seen if it works.

BTW

I confirmed that the Mustang GT reservoir cap is NOT compatible with the standard 3-prong caps used on older/previous Fords. The pressure brake bleeders won't work without a custom made cap (as in buying a spare cap and mounting a fitting).

 

I used 3 to 4 wraps, issue fixed.

 

Thanks. I will keep an eye on mine for the time being. We need to write Ford HQ and start pushing them for a fix.

 

The stock gasket is EPDM rubber.

 

I went with the new gasket route, and still got a little leaking, although not nearly as much. It is seated on so tight it takes both hands to get on and off. I noticed the fluid level was all the way to the top, so, I took the brake fluid level down to half way between the max and the min markings, and now no more leaks.

 

Is your max mark right below the top of the reservoir?

 

The max line is about 1/4" from the flat top of the resevoir. Since the top has a radius down to the side, that makes it about 1/16" below the curve of the radius on the side.

 

Thanks Buster. It seems we all have the same reservoir markings. I too siphoned out the fluid until it was halfway between the MAX and MIN marks.

 

We've been kicking this around for a while now, and it appears to be a widespread problem with '05-'07 Mustangs. The cause of the problem is simple to describe.

The top of the filler neck, where the cap gasket is supposed to seal, is not flat. Apparently, the moulding process for the plastic reservoir didn't work right. So, you can have the reservoir replaced by the dealer, and if you luck out like I did, you'll get one that seals.

Or, you can figure out a way to smooth out the sealing surface of that lip. Either by scraping it smooth with a sharp blade, sandpapering it, or whatever. Just don't get any chips or sanding dust into the fluid.

 

I remember someone posting that after putting the washer in the cap they were hearing strange noises coming from the brakes...it will be interesting to see if anyone else reports the same...

 

They are not related. Two different issues no matter what the post says.

 

Removing brake fluid makes sense with that gasket design. Shaving the neck of the reservoir doesn't seem to make a lot of sense, since the gasket is pushing down and conforming to all of the uneven surfaces. The ridges you see aren't molding defects but rather appear to be part of the design.