Brake problems

[bombapinoy]

Hi all. I converted my te72 front struts to ae86 struts, resulting in me upgrading my front brakes to ae86 calipers. When this happened My master gave out and replaced that. However after replacing that, along with the booster, the brakes were still too spongy that it would go all the way to the floor and i wouldnt really call it braking. So I replaced the soft lines in the front and also rebuilt the calipers but still the same problem. I also have bled the brakes several times. I am seriously stumped. Please help guys.

[Glock30]

Did you bench bleed the brake master cylinder? You may have some air in that. Also, was it a new master or rebuilt?

[jondee86]

Check this out
https://www.youtube.com/watch?v=_ubGaxL2F4E

Cheers... jondee86

[bombapinoy]

Yes it was bench bled and it was a new master. Have actually gone and replaced it 5 times and still the same result.

[allencr]

Where's the bleeder, top or bottom of the caliper?
Other then that it's the MC or there is actually no air causing the spongeyness but something is flexing/loose/out of alignment. Look at all 4 corners with the pedal being pumped and you'll see something obvious, if it isn't just air being compressed. The fluid has to be moving something.

[bombapinoy]

its towards the top of the caliper. And we even bled it the old fashion way with 2 people. Nothing was seen that was flexing, ballooning or such.

[yoshimitsuspeed]

Definitely make sure all the above recommendations are covered and the system is well bled. I prefer the one man technique with the line submerged in brake fluid. This allows you to quickly pump the pedal a few times in a row and can push air bubbles out of high spots that just won't move with the slow traditional method.

I don't know anything about the car or this swap to this is a completely left field thought that may or may not be applicable but if the new pistons are bigger then your master will need to travel further to move them enough to pressurize. If the master is small enough and the calipers are big enough the master won't be able to move enough volume to close the calipers enough to clamp as much as they need to.

[bombapinoy]

The TE72 and Ae86 have the same master cylinder. 13/16 bore size. Many people have done the swap to ae86 struts and im pretty sure they got the brakes working fine otherwise they would note it somewhere that I would need to upgrade the master. But would the proportioning valve be a possible cause to the weak brakes? Thats the only thing that is not new in the system

[totta crolla]

The best way to find this kind of fault is to eliminate one component of the system at a time.
Starting with the master cylinder block every outlet, make sure there is no air in this part of the system and then try the pedal. If the pedal is good move onto another part of the system and do the same. You can make up some short test pipes quite easily and one of them needs a bleed screw attached. Don't be tempted to fit a bleed screw directly to the master cylinder.
A brake pipe clamp can be used if you are still using the rubber brake hoses.

[jondee86]

If everything else checks out normal, but you had the brake master and
booster apart, chances are the booster pushrod is not adjusted correctly.



This is not a Toyota pic, but it will give you the general idea. There are
plenty of step by step descriptions on the interweb, and it is covered in
the AE86 Body Manual. Basically, you need to adjust the length of the push
rod so that when the master is assembled to the booster, the end of the
push rod has zero clearance. That means just touching, but not pressing
on or moving the cup inside the booster.

If you left a gasket out between the master and booster, or failed to check
and adjust the length of the push rod, you could be pre-loading the booster.
This will/can cause several problems, including excessive pedal travel.

Cheers... jondee86

[bombapinoy]

Ok I'll go ahead and try that out. Another problem that I'm having though is that the pedal slowly sinks to the floor. I have been led to believe that its the MC but I have replaced that at least 4 or 5 times now and still to no avail. Do you think I just keep getting a bad cylinder?

[Glock30]

Ok I'll go ahead and try that out. Another problem that I'm having though is that the pedal slowly sinks to the floor. I have been led to believe that its the MC but I have replaced that at least 4 or 5 times now and still to no avail. Do you think I just keep getting a bad cylinder?

Are you loosing fluid?

[bombapinoy]

Fluid is staying at max level and no signs of leaks.

[jondee86]

Ok I'll go ahead and try that out. Another problem that I'm having though
is that the pedal slowly sinks to the floor. I have been led to believe that its
the MC but I have replaced that at least 4 or 5 times now and still to no avail.
Do you think I just keep getting a bad cylinder?

It is NEVER a good sign if the pedal slowly sinks to the floor.

What happens if you pump the pedal ? Does it pump up and stay firm if you
hold pressure on the pedal ? Or does it sink to the floor ?

If it sinks to the floor, then you have a leak somewhere. Either internally in
the master, or externally. Since you aren't losing fluid, it would most likely
be leaking past the internal seals in the master. Kind of unlikely that you would
get several masters all doing the same thing.

If it pumps up and stay firm, then you most likely have a situation where
drum shoes or discs pads are retracting too far from the drum or disc. This
means the shoe or pad has to travel some distance to make contact, and one
pump of the brakes does not shift enough fluid. On disc brakes there is no
spring for retracting the pads, so they should be just barely touching the
discs. But drum brakes have retracting springs so you need to adjust them
until they are one click away from dragging.

Cheers... jondee86

[bombapinoy]

So what happens when I pump the pedal when the engine is off is that it stays firm. Only when the engine is running is when the sinking happens. The check valve works so i assume that the booster is fine.

[jondee86]

So, engine off, pump the pedal half a dozen times to use up all
the vacuum assist, then let it sit for a few minutes. Now press
the pedal once... does it go to the floor ?

If it goes to the floor the first pump... does it pump up and stay
firm after a couple more pumps ?

Cheers... jondee86

[bombapinoy]

No it doesn't sink all the way. But it's not as stiff as when I pumped it up a few minutes ago

[jondee86]

If you have drum brakes at the rear, see if they need adjusting. Best
way is to wind the clicker up until the drum locks, and then back the
clicker off until the drum just turns free without dragging.

Cheers... jondee86

[bombapinoy]

Thanks! I'll try that

[bombapinoy]

Yeah...still no luck.

[allencr]

It's not luck, though it sometime takes luck to get all the air out from all the little nooks & crannies & fitting's threads throughout the system. Fast moving fluid from a quick push/stab on the pedal will do that to any air anywhere in there.

[Glock30]

You may also might want to try something like a Mityvac. Might be easier for you to pull the fluid through as opposed to pushing it out.

[bombapinoy]

Finally fixed the problem guys. It was because the way i put on the front caliper. Apparently it was only a mm off and it caused my whole system to go bonkers. >_< apparently the ae86 front calipers are like that.

[allencr]

Thanks for the update, but I don't understand the solution at all.
Could you please explain it a little differently/better? Thanks.

[bombapinoy]

My mechanic told me that I had not put on the calipers properly and that it was barely loosely fitted. He wasn't able to show me but he says when i change the pads again or do something with the brakes to call him and he'll tell me exactly what i need to do to have the brakes put on properly.