Brake Pedal slowly heading towards floor after stopping

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I am interested in getting ideas as to what else might be going on with the brakes on my 2002 ZZE-122R Corolla wagon.

When I brake and come to a stop the pedal still keeps traveling towards the floor.

This is typical of a leak in the brake lines, calipers or a master cylinder problem.

I had the master cylinder replaced 14 months ago as the same thing was happening then, now it seems I have another master cylinder gone.

This seems too much of a coincidence.

I had the brakes checked this morning at the workshop that I use regularly with good results and they tried to diagnose the brake problem, but came back with the diagnosis of the master cylinder.

From what I can see there are no leaks anywhere in the braking system, brakes work well when applied, pads are not worn out, nor misaligned, but just an annoying pedal feel.

Does any one have any ideas as what else might be happening here?

Have I missed something?

Is this a problem with this model?

thanks,

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[dyslexik]

You could try bleeding the brakes again and have yourself pump the brake pedal 3-4 times according to how firm you want the brake pedal to be.

Have the brake fluid tested for moisture content (My brake specialist uses an electronic dipstick device). If it is close to 3% moisture content, it needs replacing.

[dirty hands]

I would replace the brake fluid with a dot 4 fluid or better

bleed the whole system

check for pad wear or damage/warp to discs and drums if fitted

you may have brake fade

also check the booster is working properly

to do that rest your foot on the brake pedal

if the pedal goes down when you start the engine the

booster is ok

[CHA54]

when the master was replaced last time, was it replaced with a reco unit or a new genuine unit?

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Thanks for the replies, answers below.

dyslexik

With new fluid in the system now I would assume the moisture content to be low, but will ask next time I talk with the workshop guys.

dirty hands

Brakes were all bled today with new brake fluid, not sure of the DOT value.

No warpage visible or mis-aligned pads, pads all in good shape no shudder in the pedal when braking.

No brake fade I can feel.

Booster tests fine, I checked that this morning after I got home from the workshop.

CHA54

Replacement last time was a new unit, not reco, as far as I am aware, but not an original part, will ask.

The one taken out was an AISIN.

thanks again,

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[SuperDave]

I'm leaning towards air or water in the system. Do a full fluid replacement, not just a bleed. The full replacement will also ensure there isn't mixture between various DOT levels. I'm told mixing the silicon based fluids (DOT 5) with the glycol based fluids (DOT 3+) can cause a spongy pedal. Never tried it out myself though.

[dyslexik]

Forgot to mention to also inspect the brake lines, as when worn out, would result to a spongy pedal feel.

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I have had some success sorting out the problems with my brakes.

Brake Master Cylinder was replaced with a new one (Aisin).

Motul DOT 4 fluid was used and there was a complete replacement of all old fluid.

Problem of getting the brake pedal feel right was about getting the brakes bled properly, mainly the correct sequence of bleeding.

Page 23 of http://www.pbr.com.au/technical/documents/HYDRAULICBRAKESYSTEMSGUIDE.pdf.

Page 2 of http://www.pbr.com.au/technical/documents/TBB01.pdf.

Brake Tip 5. http://www.brakemart.com.au/faq.htm

This method of brake bleeding was new to me, but it seems to have fixed the soft pedal.

Thanks,

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