Brakes not working - brake pedal sinks

tookien · Jun 19, 2018

I did a little test to see if it's indeed the banjo washer.

I crimped the brake hose again on the front right wheel.

And then bleed out the system from the other wheels.

My prediction was that some pressure will start to build up at the pedal.

But it didn't.

I will replace the banjo washers anyhow, but I think the issue is somewhere else.

I hear that if air gets introduced into the ABS module, only way is to bleed it out. The mistake I regret is forgetting to check if the reservoir was topped off at the M/C before bleeding.

One method is to use the tec 2 scan tool. Which I don't have.

Another is to bleed it out manually somehow (which I've never done).

Another could be to trigger the ABS by driving the car around in slippery conditions - this may trigger the auto-bleed.

I'll start to work on it later today and see if anything solves it.

tookien · Jun 19, 2018

The fuse was out for the ABS before I did the job.

Does that count as disconnected?

das_peikko · Jun 19, 2018

Originally Posted By: tookien
The fuse was out for the ABS before I did the job.

Does that count as disconnected?

No. I was referring to the fluid lines that go to the ABS module. If you unhooked those for any reason, then it's possible that air was introduced into the ABS module.

chrome · Jun 19, 2018

Originally Posted By: tookien
I hear that if air gets introduced into the ABS module, only way is to bleed it out. The mistake I regret is forgetting to check if the reservoir was topped off at the M/C before bleeding.

This is likely the reason why you have air trapped in the system. When you started bleeding the system with a low reservoir level, you introduced air into the ABS module. You will need to look up the factory procedure for bleeding the ABS module, and proceed from there.

Ducked · Jun 19, 2018

Originally Posted By: tookien
The brake fluid is present in all 4 calipers, while bleeding.

The fluid is filled to the top.

If you've got air bubbles, which you said you had, then it isn't filled to the top.

Get a syringe.

Remove some fluid from the master cylinder reservoir by pulling it into the syringe.

Push it into the calipers at each corner using the syringe.

If you keep doing this, occaisionally cycling the fluid in and out with the syringe, there is a very good chance you'll purge any air.

Then you can find out if your master cylinder is buggered.

Caveat: I dunno if this will work with an ABS. Never had one, but I understand they are a PITA.

mk378 · Jun 19, 2018

When all the fluid is allowed to run out, air will get into the ABS module the same as if you had disconnected the lines at the module. You must follow the ABS bleeding procedure.

tookien · Jun 19, 2018

To update, I replaced banjo washers on the front right caliper with new ones.

I then proceeded to bleed out the air from all 4 wheels (again), this time using a one-man bleeder tool.
No air bubbles were left, just consistent fluid.

But the pedal still falls to the ground with little to no resistance so bleeding at the calipers definitely will not solve the issue. And there are definitely no leaks.

Same problem.

My next step is to bleed out the master cylinder, but the main brake lines are fairly stubborn to get off and I don't want to damage them.

I cleaned the lines at the M/C ports and sprayed some lubricant, hopefully it will penetrate enough so the lines will be easier to remove.

I am interested in using the syringe method Ducked mentions above.

tookien · Jun 20, 2018

Hi Ducked,

with your syringe method, do I have to pump the fluid I take out from the M/C back into the calipers?

is that through the bleeder valves?

thanks

tookien · Jun 20, 2018

I'm leaving the ABS module for last after I test the M/C.

From my research the ABS module is the least likely to be the case.

maxdustington · Jun 20, 2018

Originally Posted By: tookien
Hi Ducked,

with your syringe method, do I have to pump the fluid I take out from the M/C back into the calipers?

is that through the bleeder valves?

thanks

You do not need to reverse bleed the entire system, bleed your MC.

das_peikko · Jun 20, 2018

one- man bleeder tool? What kind?

Ducked · Jun 20, 2018

Originally Posted By: tookien
Hi Ducked,

with your syringe method, do I have to pump the fluid I take out from the M/C back into the calipers?

is that through the bleeder valves?

thanks

Yes. Fluid will well up into the master cylinder reservoir, hopefully taking any air with it.

Alternatively, you can just suck it out via the caliper and then push it back in again. If you suck any bubbles out (they may be entering via the bleeder threads rather than originating in the system. Bit of PTFE tape might help with that) its easy to avoid blowing them back in again simply by tilting the syringe.

I've heard that this can evert mc seals but I've never managed it and I've used as nmuch pressure on the syringe as I could exert, though now I use less.

Vikas · Jun 20, 2018

Originally Posted By: das_peikko
Originally Posted By: tookien
Does anyone think the ABS module needs to be bleed out?

Not unless you disconnected the ABS module.

I think the old banjo washers are killing you. They take up an impression every time they're clamped on. When the new impression doesn't line up with the previous impression, you'll get air entering through the previous impression. I've had it happen to me before I was educated about banjo washers.

If the air is entering in there, the brake fluid has to leak out of there! Is that what is happening? OP says no.

Vikas · Jun 20, 2018

if there is air in abs and brakes are barely operating, you really can't use the slamming on the brake to engage ABS pump to purge the air. You will NOT be able to lock up the brakes to activate ABS. You will need fanciest scanner to instruct ABS pump to run. I do not know if there are any alternate ways for that.

das_peikko · Jun 20, 2018

Originally Posted By: Vikas
If the air is entering in there, the brake fluid has to leak out of there! Is that what is happening? OP says no.

That's what I thought when I had the leak. There was no fluid to be seen anywhere in the immediate vicinity of the brake hose or caliper; little did I know that all the brake fluid was getting sprayed from the banjo washer to the tire!

tookien · Jun 21, 2018

Okay guys,

I'm about to go crazy.

I took off master cylinder and bleed it out.

I put it back in.

Now something weird is happening.

There is a hissing noise coming from the brake booster (when the car is turned on).

And the pedal still goes to the ground (car on or off).

I thought it might still be the master cylinder.

I got another master cylinder. Bleed it. Put it in.

Same thing.

Hissing noise coming from brake booster.

I know it's coming from the brake booster because if I disconnect the vacuum line going to it the noise stops.

This time I cannot even bleed the brakes on each caliper, whereas before I could.

The m/c is firmly mounted and lines are hooked up properly.

Any really good advice on this would be greatly appreciated as the car now has zero brakes.

tookien · Jun 21, 2018

I also confirmed no leaks from the banjo washer or hose or line as I thoroughly checked for leaks while someone was pumping.

das_peikko · Jun 21, 2018

What kind of one-man bleeder system are you using? If it's speed bleeders, that's you problem.

tookien · Jun 21, 2018

Hi Das_pelko,

I am using this one: http://www.canadiantire.ca/en/pdp/1-man-brake-bleeder-kit-0250131p.html

It takes lots of pumping to get the air out with that.

But it takes even more pumping it with 2-man method.

This is what is so weird, usually bleeding out the air doesn't take so long.

I've bled it out so many times now (4-5) a combination of one-man and two-man bleeding operations.

going through many quarts of brake fluid.

And still the same problem.

tookien · Jun 21, 2018

das_peikko,

as I said I primarily use the two-man bleeding method.

but that didn't work - I've done the process dozens of times before successfully.

then I also tried the one-man bleeder.

for each wheel, I can see the fluid passing through with the air bubbles. then after a while of pumping no more air bubbles and the fluid is consistent.

that is where I stop the bleeding process at each wheel and close the bleeder valve up.

I still question whether it could be the master cylinder causing the problem.

When I bleed the m/c out it takes some pressure and the fluid comes up from both ports, air bubbles come up and then after about 5-8 pumps no more air bubbles and constant fluid. that is where I stop bleeding the m/c and then reinstall into the vehicle, mount it on the brake booster and connect the lines up.

I'm already ordering a brake hose for the front right to eliminate that, but I don't think it's the problem as I do not see any leaks anywhere.

Right now I'm going to cap off the master cylinder ports, to cancel out the brake lines and to see if the pedal still goes down.

If it does then it's still a problem with the master cylinder.

If the pedal doesn't go down, then it must be the brake booster.

Also, do you know if there is a gasket going between the m/c and brake booster?

I didn't see one when I took off the original. I mean, if there is supposed to be some seal or it's supposed to be torqued down really high, that might explain the noise.

but the symptoms from the brake booster, the idle (after change in vacuum line), the hissing noise, it all sounds like the problem is in fact the brake booster.

except the fact that the pedal shouldn't sink but should stay firm.

if it was the brake booster the pedal should be firm.

but it sinks.

but the rest of the symptoms of a faulty brake booster matches.

which makes it that much more confusing.

Brakes not working - brake pedal sinks

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