Here's a picture of the High Pressure Fitting elbow end (The one that fits into the Rack & Pinion)
(MN12) Bad High Pressure Fitting.JPG
There's a few different reasons these things leak..Let's discuss the most common reason first..
There is an O-Ring underneath the fitting that eventually goes bad due to heat/chemical compatibility/shrinkage/swelling, many things..
When this O-Ring fails..The solution by Ford is to just replace the whole elbow..The O-Ring was never a serviceable part..
Moving on..The next most common reason these things leak are..The Teflon Seal goes bad..
Normally this seal doesn't just go bad on its own unless it's messed with..The Teflon Seal is one time
So if you have to remove this fitting off of the rack..The Teflon Seal must
be replaced before reattaching the fitting back onto the rack..
When you install the replacement Teflon Seal..Warming it up in warm water is suggested to make it more pliable to fit just over the threads of the fitting..
Probably the least common way this fitting fails is if it gets cracked in half..Perhaps from a combination of rust, or just being too rough on the part..
All 91-97 Thunderbirds/Cougars used the same fitting..As well as all 93-98 Mark VIII's used this same fitting as well..
IMO..If you can afford to it's best to use a Ford piece here vs Aftermarket..
The Ford Part Number for the High Pressure Fitting is: (F1SZ-3A719-D) or (F1SZ3A719D)
The Ford Part Number for the Teflon Seal is: 388743-S100
The High Pressure Fitting is still available new from your local Ford dealership, or online..
Unfortunately the Ford Teflon Seal has been discontinued..
You can find a replacement Teflon Seal at your local auto parts store..Dorman Help Part#82540
IIRC..You use the smaller of the 2..
The aftermarket Edelman High Pressure Fitting is part #39141
In closing..If anyone has replaced the O-Ring seal in this fitting that commonly fails, and was successful (meaning it didn't leak)
Please post a part number, and or size of seal you used..