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Discussion Starter · #1 ·
With the car back on the road, the problem it had with the brakes before I parked it is still there. They are very squishy, require lots of pedal travel to start doing their thing. I replaced the battery cylinder thinking that was the culprit but it made no difference.

What has been replaced:
  • Front calipers
  • Front lines
  • Master cylinder
I originally replaced the front calipers because one was seized. The rears seem ok. I should replace the lines out of safety but they don't show any obvious immediate issues.

Thoughts on the squish? My car has ABS but it is non functional due to the manual swap.

I am considering just bypassing the ABS module - is it possible thats the source of my issue?
 

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1987 Toyota Supra
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Could just have air trapped in the ABS system. Might need to perform a good flush or manually activate the ABS motors during the bleed procedure.
 
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I would expect w ABS, the brakes would act and feel normal until it activates. So if the module is not intervening, it should be in default mode which is normal operation. Stock brake system other than this?
 

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Discussion Starter · #4 ·
I would expect w ABS, the brakes would act and feel normal until it activates. So if the module is not intervening, it should be in default mode which is normal operation. Stock brake system other than this?
Completely stock, 3rd party but OEM calipers, master cyl.

Reading about people having issues bleeding the ABS system when it doesn't work, there's a way to activate it:
brake bleeding through ABS
 

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Smith & Wesson Member
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Make sure the vacuum booster hose is not a soft type hose. It will collapse under hard vacuum pressure.
 

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89 Supra Turbo M/T
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Did you bleed the rears? I've ran into a similar issue on another car when replacing only the fronts and bleeding the rears fixed it. Now when I bleed brakes, I start with brake furthest away from the master cylinder and work my way towards the closest. No idea how air would get into the rear line when replacing the fronts but there's a lot stuff I don't know. 🤷‍♂️

Oh, how are the pads? I drove a Tundra with very low pads and it felt squishy.
 

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Master Shit Fixer
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Squishy is air in the system. Did you bench-bleed the master cylinder before installing it? Did you bleed the entire system correctly? You might want to take the car to a shop that has a pressure bleeder to bleed the entire system at once.
 

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Monitoring this thread...
Took all my brake hardlines out to paint the engine bay, ABS out, master cyl too. Mercedes brakes up front w/ss lines.
Put it all back in this weekend. Didn't bench bleed shit.
First I gravity bled it: filled the master cyl and left all the bleed screws open on the calipers. Then I started from the rear passenger caliper with a vacuum bleeder, hit every corner. Then I went back and power-bled it with my brothers:
(1) Bleed screw shut- pump pedal 5 times, hold it to the floor
(2) Open bleed screw for a sec, watch for bubbles, then close bleed screw.
(3) Repeat 1&2 until no more bubbles. Move to next caliper. Make sure the fluid level in the master cyl doesn't go below 'min' ever.
The pedal is rock hard, and the brakes work excellent (no engine, so I only tested them by rolling the car around). I wonder if I'll have to bleed the ABS pump too, since I removed and reinstalled it completely. Everything seems to work fine as of right now though.
 

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Discussion Starter · #9 ·
Thanks everyone. Sounds like I just need to give it hell again with the bleeding. I'll give it a go again with some gusto and see where that gets me. Really should probably replace the rear lines while I'm at it.

Side thought, it seems like I could get the ABS back up and working potentially if I hook the R154 side pigtail into the car harness (A340E) side. Same 3 wires just different plug, seems like a solvable issue- anyone have experience making that work on a trans swapped car?

Font Parallel Rectangle Automotive design Drawing
 

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I don't know if this applies to the MkIII also, but on the MkIV, since the ABS unit is nonoperational when stationary, the bleed procedure is to turn the key to ON and bleed within 10 seconds (IIRC). My assumption is that the ABS part of the lines is completely open for the 1st 10 seconds after the key is turned to ON, thus allowing you to bleed though the entire system, including ABS, for 10 seconds.
 

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^ Normally, you shouldn't have to involve the ABS system. It's unlikely that air can get in there naturally. But if you've removed the lines going to the pump, that's another story.
 

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Start bleeding the longest line first which would be the passenger rear, then the driver rear, then the passenger front, then the driver front. Bleed until no bubbles or discolored fluid comes out. I use a one person bleeder that has a check valve in it and a hose that leads to a collection bottle. A rubber sealing grommet slips over the bleed nipple that the hose slips inside of. The hose is clear plastic so I can pump it by hand and look under the car while it's bleeding. Use full strokes of the brake pedal top to bottom. Just keep an eye on your reservoir to top it off and don't run dry. I've had good results with Valvoline DOT 3 & 4 synthetic brake fluid.
 

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Discussion Starter · #15 ·
I am recalling now as I think back, when I bled the car the front was up on jackstands. I'm sure that didn't help anything...

I have an electric vacuum pump I'll employ as well just to see if it can help.

I'll keep the thread updated when I get it done, but I just put the car back up on jacks because I need to pull the turbo...
 

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Bleeding brakes, one of my less favorite jobs out there... hydraulic fluid has the strange property of being really slippery while at the exact same time, making things weirdly sticky. Never did understand the stuff. :p

Related note, don't let it get on painted surfaces, it's quite corrosive! Clean it up as soon as possible so it doesn't ruin paint. Also, it's hygroscopic, use that to your advantage if you need to clean in a spot you can't quite get to, by which I mean, a spray bottle filled with water is your friend here.
 

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1986.5 black/tan N/A auto
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You should try replacing the brake booster, mine had brakes that didnt engage until past the halfway point and then they would grab a little more than expected. I replaced the master cylinder first, then the 2 front brakes with 4 pistons and eventually found a junk supra that had a booster which fixed the problem.
 

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Discussion Starter · #19 ·
Found the rear brake lines I bought 4 years ago... literally 30 minutes AFTER I ordered a replacement set.
Cancelled my order for those...
I get those swapped then just give it hell with a good flush. I think it'll come around I just need to get in like I mean it.
Keep you all posted....
 

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Discussion Starter · #20 ·
You should try replacing the brake booster, mine had brakes that didnt engage until past the halfway point and then they would grab a little more than expected. I replaced the master cylinder first, then the 2 front brakes with 4 pistons and eventually found a junk supra that had a booster which fixed the problem.
Hopefully I don't have to, but I will definitely check on that if I can't get them tight. Thanks!
 
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