Converting '87-88 Turbo Coupe from ABS to vac-assisted brakes

November 28, 2005, 07:41:10 PM

Thought I'd post this up since I've had several people ask about doing the conversion.

I used a '89 5.0 Mustang brake booster (and by the way, I had almost no problems getting this booster in without removing anything. Biggest problem is that some of the wire bundles like to fall behind it when you're trying to seat it against the firewall). I also used an '85 lincoln town car master cylinder (1" bore), but I would recommend using an SVO master cylinder (or something with an equivalent bore size) because the pedal is mushier than I would like.

Getting the old master cylinder out and the new booster in is honestly the hardest part. You can tee the lines off the rear port of the MC so you don't have to buy a proportioning valve. However, you have to get a metric tee and a metric female-female union for the tee. I found all my adapters but one at Napa, but I had to go to 2 different stores. The metric tee, I actually picked up part #7919, the metric fittings on this tee are the right size but it's only got a 3/16" inverted flare fitting on the side. I meant to get one with a 1/4" flare fitting but I wasn't paying attention and didn't feel like driving back into town to exchange it so I just used another adapter. Advance Auto parts carries the 3x16"x10-1.0 union that you need.

Now this is where things get a little complicated. For starters, the thunderbird's factory prop valve has a 3/16" inverted flare fitting on the rear and a 5/16" fitting on the front, so you'll need an adapter fitting for the front. Also, the early style MC's (ones without a plastic reservoir) have standard fittings on them, while the later model ones (with plastic reservoirs) have metric fittings. You can get metric-standard adapters but not the other way around, don't ask me why. Also you can get lines with metric "bubble" fittgs on one end and standed inverted flare fittings on the other end now, which would make plumbing in one of the newer MC's a lot easier. Anyway, you'll have to connect the "third" brake line (the one that runs to the driver's side front caliper) to one side of the tee, and the other port on it will be connected to the rear port on the proportioning valve. I happened to buy a complete '89 5.0 booster & MC with all the lines which provided me with a line to run from the tee to the prop valve. Otherwise, you'll have to get one of the aforementioned lines (metric on one end, standard on the other) and bend it up to fit here. The front port is easier, since you just run a line from the front port of the MC to the front port of the prop valve. On the Lincoln MC, the front port on it was 5/16" also so I ended up adapting it to 1/4" line and running that. I also ran a 1/4" line from the rear port to the tee. Obviously, other master cylinders will be slightly different so I recommend taking the master cylinder with you when you get your adapters and lines, just to make sure you have everything you need.

Finally, for the vac source for the booster, I just teed off that black plastic line that runs from the upper intake to the vac tree. A short length of 3/8" rubber hose and a 3/8" vacuum tee from Advance are all you need.

If you want to remove the wiring and such for the ABS, you're on your own. I decided I didn't feel like going through all the hassle required to pull out a couple pounds of wiring.

Hopefully I didn't forget anything!

Converting '87-88 Turbo Coupe from ABS to vac-assisted brakes

Reply #1 – November 28, 2005, 08:35:49 PM

Coolbeans. I plan on doing this too... not that I don't trust that super expensive electric pump...... :rolleyes:

thanks for the write-up. :)

Converting '87-88 Turbo Coupe from ABS to vac-assisted brakes

Reply #2 – November 28, 2005, 11:08:45 PM

Yeah, I tell ya what figures...maybe 2 months if that after I drop my new engine in, something in my pump system took a dump on me. New relay didn't fix the problem so I figured it was either a problem with the wiring, or a problem with something in the master cylinder- neither of which I particularly cared to try to chase down:disappoin The system had sorta been on the fritz for a little while before that, though.

Woulda been a hell of a lot easier to do without an engine in the engine bay, but isn't that just how things seem to work?

Now I'm enjoying my computer-free braking system.