Sanity check--XR Brake Bleeding

[ssacamp]

I think i've read all the previous threads on brake bleeding but I'm stumped. Bought a project '88 XR that had been sitting for many years. Not bad condition overall. Changed fluids,filters, ignition parts,etc and she fired right up and idles perfect. Right front caliper was stuck. Rebuilt the caliper and flushed all the brake lines with new Dot 3 Motrocraft fluid. Rear brakes appear to be Turbo Coupe discs. I loosened the rear calipers and got their bleed screws up top. Started with the right rear and bled the longest lines first, being careful to keep the MC level up.
I've bled these darn lines 3X now. Two times using my compressor and once by gravity. I bench bled the MC today on the car, from the left front caliper to the MC. Brake pedal still goes to the floor. Either the MC is bad or I'm doing something wrong. Any ideas? Thanks.

[my8950]

Master cylinder may be bad in that case.
I recently got to use one of these power bleeders which uses an air compressor to pull the fluid through the lines.
I'm pretty impressed with that as I've never been a fan of bleeding brakes.
Some how or other, my dad manages to do it by himself and not have any issues.

[andyofcolumbusmerkur]

I'd check with the vendors here and see what they have available. Decide if it makes sense to get a rebuilt MC or a rebuild kit, or possibly adapters for the larger thunderchicken MC. In the past I have damaged a MC from pumping the pedal during the bleeding procedure. This was because the car (a taurus) sat awhile and wasn't in great condition. Putting the pedal all the way to the floor over and over damaged the seals inside and fluid escaped into the brake booster.

[ssacamp]

The compressor does a good job of pulling the old fluid out and the new in but I'm actually concerned that I may have damaged the MC by using too much air pressure/vacuum. May have to get a MC seal kit from MPW or have Jeff rebuild the MC.

[my8950]

I'd check with the vendors here and see what they have available. Decide if it makes sense to get a rebuilt MC or a rebuild kit, or possibly adapters for the larger thunderchicken MC. In the past I have damaged a MC from pumping the pedal during the bleeding procedure. This was because the car (a taurus) sat awhile and wasn't in great condition. Putting the pedal all the way to the floor over and over damaged the seals inside and fluid escaped into the brake booster.

Why get the thunderbird MC when the one used in the Scorpio is the same as the unit used in the Sierra's in Europe?
If you decide that you are interested to go this route, let me know as I have a few more of these available right now, with harness.

[ssacamp]

Helpful info, thanks guys!

[reddy2300]

I think i've read all the previous threads on brake bleeding but I'm stumped. Bought a project '88 XR that had been sitting for many years. Not bad condition overall. Changed fluids,filters, ignition parts,etc and she fired right up and idles perfect. Right front caliper was stuck. Rebuilt the caliper and flushed all the brake lines with new Dot 3 Motrocraft fluid. Rear brakes appear to be Turbo Coupe discs. I loosened the rear calipers and got their bleed screws up top. Started with the right rear and bled the longest lines first, being careful to keep the MC level up.
I've bled these darn lines 3X now. Two times using my compressor and once by gravity. I bench bled the MC today on the car, from the left front caliper to the MC. Brake pedal still goes to the floor. Either the MC is bad or I'm doing something wrong. Any ideas? Thanks.

The TC rear calipers are the absolute worst to try to bleed. I had one with them and can't remember what I had to do to get them bled. I do remember having to do it many times, though.

Dumb question: The calipers are installed with the bleeder at the top, correct? If I remember correctly, they need to be swapped side to side to make sure the bleeder is as high as possible.

(I think I pulled the caliper partway off to raise the bleeder. Need to still put something in there to mimic the rotor being in place. Very bad things happen if you don't.)

[ssacamp]

Thanks for the feedback. The rear (TC) bleeder screws location on the caiiper are low on both sides. So each time I bled them I unbolted the calipers, slid them carefully up the rotor to where the bleeders were at their highest point. I'll be getting a MC seal kit from MPM when Jeff gets more in and I'll try that.

[andyofcolumbusmerkur]

Ya I remove and flip my rear calipers to bleed them. It's an extra step but not a huge deal. The RS500 used that Scorpio type MC (I believe the exact same unit) so they would have brakes while racing and into the boost. That's another option as long as the unit is still in good working order.

[Ed Lijewski]

I bought a compressor vaccum bleeder and was dissatisfied with it. I bought a basic model, ~$25+ IIRC, maybe higher end products work better, and maybe my smallish compressor isn't strong enough.

So I bought this power bleeder. Atttach to the MC, pump it up, bleed brake. ~$55/Amazon.

Screenshot_20240210-182929_Chrome.jpg (443.42 KiB) Viewed 641 times

https://www.amazon.com/Motive-Products- ... 4gQAvD_BwE

YMMV

[ssacamp]

I had watched a couple youtube videos re brake bleeding using the power method. Somewhere I saw a recommendation to use about 40lb pressure in the air compressor. Now I'm reading that 15lb is about right. That may have been my problem with the "power" approach; too much vacuum. I was never quite sure all the air was all out of the lines because the fluid in the catch container always had air bubbles in it. I may try the power method again at lower pressure to see if that works or just wait on a seal kit for the MC from MPM. Its feeling futile at this point.

[my8950]

I had watched a couple youtube videos re brake bleeding using the power method. Somewhere I saw a recommendation to use about 40lb pressure in the air compressor. Now I'm reading that 15lb is about right. That may have been my problem with the "power" approach; too much vacuum. I was never quite sure all the air was all out of the lines because the fluid in the catch container always had air bubbles in it. I may try the power method again at lower pressure to see if that works or just wait on a seal kit for the MC from MPM. Its feeling futile at this point.

The 15 sounds about right from my poor memory. I borrowed a Snap on bleeder from work and used that, the air compressor I have is 80Gallon though, to make sure you don't run out of compressor.