If the brake fluid is flowing normally through all four corners, I would advise you to leave good enough alone. Based upon your latest description, performing a reverse bleed procedure is probably unnecessary at this point since all air now appears to be purged.
Corolla brake pedal sinking to the floor - master cylinder?
- Thread starter jsean
- Start date
Check to see if you have any tiny leaks at the wheel cylinders. My neon had both the rigjt and left rears leak.This is on the ‘05 Corolla. Gradually lost pedal feel on the way back from work last week. Pedal would sink almost to the floor but not quite. Between this and the Armada oil change with particles what not, things seem to be going poorly vehicle related
No visual leaks at the wheel cylinders or the calipers. Jounce hoses look fine. Level in reservoir didn’t drop.
All of which led me to believe it was the master cylinder, so I ordered one off RA.
Swapped it in after work today. I followed the instructions for bench bleeding (keep it level, fill up the reservoir, let them fluid start dripping out of both ports, cap the ports, firmly push the plunger an inch and look for bubbles), verified no bubbles in reservoir and the plunger was stiff except for maybe 1/8” movement.
Got it on the car which was a challenge with the back/rear hard line. Master cylinder did get a little low during getting it in the car - i kept it topped except one time it dropped a hair below the min line.
Tried bleeding the brakes - I have marginally better pedal travel. I’m able to get clean flow of fluid out of the RR, RF and LF bleeders. I’ve gone through about 48oz of brake fluid on the LR bleeder and I still keep getting bubbles.
Anyone have suggestions on how to proceed? I’m completely lost on this one…
Good suggestion - I verified this evening that the wheel cylinders are dry.
SammyChevelleTypeS3
$50 site donor 2023
You gotta be close. Did you try grease or even Vaseline dabbed on the fitting you were getting air bubbles from? That should prevent any bubbles being pulled into that line and end your issue. Hope so.....................
You’re correct - the last picture was with the bleeder still open. I did single person bleeding - basically have the bottle filled with fresh brake fluid, crack open the bleeder and pump the pedal. I guess im not sure how much of these minute bubbles have been sucked in through the bleeders.
Should I bleed it again with a dab of grease just to be double sure?
didn’t try Vaseline / grease. I’ll give it a shot this weekend or early next week and hopefully she’ll be good as before
Not all cars need bench bleeding but yours does, per the instructions with the M/C.
Why?
Because of where the output ports are tapped on the M/C. Firewalls tilt back, so if the output port isn't on the forward most corner of the hydraulic space, you get a bubble there that won't ever leave during on-car bleeding.
So you bench bled at least ok, it sounds like. But you have to, or nothing downstream of the process works. If I ever had a stubborn M/C I'd probably get a dishpan, gallon of fluid, and dunk the entire thing underneath to bench bleed from every angle.
The issue comes from reading online others' experiences that aren't with a 2005 Corolla. Their plumbing will be different. There will be one or more creative techniques that will work though.
Toyotas are known for mushy brakes. 1/2" of play might be the best you can get.
Why?
Because of where the output ports are tapped on the M/C. Firewalls tilt back, so if the output port isn't on the forward most corner of the hydraulic space, you get a bubble there that won't ever leave during on-car bleeding.
So you bench bled at least ok, it sounds like. But you have to, or nothing downstream of the process works. If I ever had a stubborn M/C I'd probably get a dishpan, gallon of fluid, and dunk the entire thing underneath to bench bleed from every angle.
The issue comes from reading online others' experiences that aren't with a 2005 Corolla. Their plumbing will be different. There will be one or more creative techniques that will work though.
Toyotas are known for mushy brakes. 1/2" of play might be the best you can get.
I'm not sure that is needed at this point if the brakes feel normal. If you feel better doing so, it won't hurt anything, but I would suggest getting a helper to push the pedal while you work the bleeder screw. Once you are done, wipe the grease off the nipple with a rag so it won't collect dirt (like a Zerk fittings). Don't worry about the tiny bit of residual grease left in the crevice between the cylinder body and the base of the bleeder screw as that will keep moisture out of the threads.
OP if you're satisfied with the brakes now leave well-enough alone 
Or consider driving it for a week then reassess. At least for me I become hyper sensitive to such things. I try to ask myself if I just hopped in this vehicle for the first time for a general test drive, would Problem X even occur to me?
Or consider driving it for a week then reassess. At least for me I become hyper sensitive to such things. I try to ask myself if I just hopped in this vehicle for the first time for a general test drive, would Problem X even occur to me?
The fluid didn't leak back into the booster, did it?
Figured I give it a shot anyways - applied greased on the bleeder threads and confirmed no air bubbles and none of the small bubbles were present this time caused by air leakage around the threads. Figured this is about as good as the pedal is going to be. Gives my OCD a break knowing that I ruled out the potential effect of the tiny bubbles.
Wife said the same lol. Couldn’t tell any different when she drove it, but we did the 2 person brake bleed this morning and with grease on the bleeder threads. Funny enough - I can’t tell any difference in pedal feel between yesterday evening and this morning after this last bleedOP if you're satisfied with the brakes now leave well-enough alone
Or consider driving it for a week then reassess. At least for me I become hyper sensitive to such things. I try to ask myself if I just hopped in this vehicle for the first time for a general test drive, would Problem X even occur to me?
Confirmed that there was no leakage into the booster. The o-ring and the mating face were both dry.
I think you’re right. This is about as good as the pedal feel gets. Week and a half of driving my 940 had me spoiled with a nice firm pedal feel.
I think between bleeding the system several times, I think have gone through about 112oz of new brake fluid vs. supposed total system capacity of 32oz. I doubt at this point I’d have air trapped in the system.
It’s resolved, thankfully.
Brake fluid flushes were done at the dealer at 50k and 100k miles. I’ve done the brake bleeds at 140k, 170k and now at just over 200k miles.
Similar threads
