Brakes 89 GT sudden no brake pressure

While driving last night I went to brake and got nearly no response from the pedal till it was almost bottomed out. Pumping the brakes builds enough pressure to stop. Checked the reservoir today and it’s empty. Right now with car running if I pump and hold the brakes the pedal sinks a bit after. There doesn’t seem to be a leak anywhere. How can I tell if it’s the booster or master so I can get this fixed?

Yes, stock drums. I’ll take a look now.

I checked passenger rear drum, looked clean.

Followed brake lines up to passenger front. A little towards the front from where the fuel and brake lines come together I noticed a small stain on the floor. And some splashing behind the passenger front wheel well that wasn’t uniform with the drivers side. Where the subframe meets the plastic of the inner wheel well there is a drip of yellow fluid. There is quite a bit of yellowish fluid on the subframe as well.



I’m guessing there is a leak, somewhere behind the wheel well plastic. Ran out of time tonight, but I will follow up when I can get back in there and see what’s going on.

Mustang5L5 said:

That would be where the single brake line to the rear brakes comes down from the firewall area.

I'd say you found your leak

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So, I obviously won’t know what the exact situation is till I can tear into it on Monday, but is this something I can plan on working on myself or should I just take it to a shop?

I have a couple quick questions:

1. My plan is to cut the bad portion of the line out and replace it with new. Is this ok, or should I be replacing the entire length fitting to fitting that has the leak?
2. What size diameter are the lines (89 GT stock brake setup)?
3. What kind of flare, double or bubble?
4. Will the auto parts store have new fittings? I found the lines listed online, but can't seem to find if they have the fittings.
5. As far as I've found, this is what I'll need to complete this job. Am I missing anything, or using anything unnecessary?
-new brake line spool. My local store has coated steel.
-new fittings
-dot 3 fluid (not sure how much I'll need, but I'm assuming the system is nearly dry)
-line/flare nut wrenches
- flaring tool
-line bender
-line cutter/deburrer
-vacuum pump

Thanks again for all the help. I'm hoping to have this and my FPR replacement done tomorrow, which will keep me right on schedule for solving all the preexisting problems just in time to put the car away for the winter!!!