Broke the brakes while bleeding them..

[wordnz]

Today I was changing the brake fluid, bleeding the new fluid through (with help from my dad). Did the left side fine, then in the middle of doing the right side the pedal just went to the floor, even with the bleed valve closed.

No fluid is leaking anywhere. was topping up master cylinder all the time, so it didn't gulp any air in there. Brake pedal is very soft, can easily push it to the floor with your hand. When the car is running you can push the pedal to the floor with your little finger.

I'm guessing that the master cylinder seal has broken? What about the booster? (I don't really know much about this).

Car is a 1992 Toyota Levin 4AGE if that helps.

[allencr]

I'm guessing that the master cylinder seal has broken? What about the booster?

Yep, good guess. If you read many old WWW posts, the failure when bleeding happens because the MC is being worked at the bottom of of its bore, with corrosion and/or smegma down there to chew up or unseat the seal/s.
The booster has solid pieces straight through, with about 1mm or less of give for its valve. It can't cause your symptom/s.

[YeMs]

100% sure you arent loosing fluid any were? pay just to fire it up and give it about 10 pushes to the floor and make sure the fluid level isnt dropping. if the level doesnt drop at all then yes its the master cylinder and either a replacement will need to be fitted (second hand can be fine, if off a wrecker make sure they will warranty it.. can be a super pain in the ass though and half the time not worth it and getn a new item is much better) repco/partmaster/bnt do new items. or can get it rebuilt.

if the level DOES drop then you will have a leak somewere. either 1 of your nipples isnt done up proply or its leaked out a seal somewere.

Thats pretty much the only options. fluid cant 'by pass' in a caliper or wheel cylinder, only leak out.

your booster wont be the issue. all they do is use engine vacuum to increase the pressure that is applied by the foot brake. worst case scenario if failed the pedal will pump up hard and the brakes will feel 'less effective' and require more foot pressure to work as well.

[matt dunn]

What about the option that the pedal was released while the bleeder was open and now it has a big lot of air in the caliper?

That could make the pedal go to the floor.

[Quint]

Keep bleeding it to see if it is just a big air bubble.
Otherwise replace it, or if you can't (due to price, 1500rrp ex japan delio) pull it and give it a hone and some new seals ($5), wont last forever but should give you another 12-18months.

Alternatively, you can get it re-sleeved with stainless (no more pitting, yay) for about 120.

[wordnz]

Thanks for the advice so far guys. Had another check today, and there definitely isn't fluid leaking anywhere.

Pumped the pedals heaps of times 20+ and it still goes to the floor

Master cylinder level isn't dropping.

Yep, good guess. If you read many old WWW posts, the failure when bleeding happens because the MC is being worked at the bottom of of its bore, with corrosion and/or smegma down there to chew up or unseat the seal/s.
The booster has solid pieces straight through, with about 1mm or less of give for its valve. It can't cause your symptom/s.

Yeah, my dad talked to his mechanic today and he said the same thing. What should I do to avoid this in future? Just don't push the pedal all the way down when bleeding?

What about the option that the pedal was released while the bleeder was open and now it has a big lot of air in the caliper?

That could make the pedal go to the floor.

If that was the case, would pumping the pedal 10 or so times make it go stiffer? We pretty much can't get anything to come out the bleed nipple.

Time for a trip to pick a part for another master cylinder I think.

[wordnz]

Do the superstrut and non superstrut models have a different master cylinder? Not having much luck with google, getting conflicting information.

[KinLoud]

From comparing master brake cylinders from AE101 20V and supercharged Levins/trueno at pick a part.
Same master cylinder for both.

Ken

[wordnz]

From comparing master brake cylinders from AE101 20V and supercharged Levins/trueno at pick a part.
Same master cylinder for both.

Ken

Thanks, went to pick a part today and got one.

[rollaholic]

i think you'll find new ones to be relatively affordable for the peace of mind it'll give you.

plus repeating the same trick with a new cylinder is alot harder