Ke70 mysterious brake fade

**J0RD0** · 21-10-2011, 02:38 PM

I have a mysterious brake fade in my corolla which im trying to find the source of the problem. When braking the pedal is hard but after a few seconds of sitting with my foot on the brake it goes to the floor

Its a 83 ke70, the problem started before the front struts were replaced with T18 items and new front brake hoses, the master is only 2 yrs old since being rebuilt. I checked the rear wheel cylinders for leaking brake fluid. The flexible brake hose to the diff is in good condition with no cracks or visible leaks, and the fluid has been flushed and bled recently

Im stuck on where to look next

Can anyone tell me what would cause something like this to happen and what i han look for to fix it or even some test's to try and find the problem?

any help appreciated

**thechuckster** · 21-10-2011, 04:07 PM

m/cylinder ...

**J0RD0** · 21-10-2011, 06:58 PM

you certain? its not loosing any fluid and has been rebuilt 2 - 3 yr ago. Can they go that quickly after being rebuilt?

**Rens** · 21-10-2011, 07:12 PM

How old is the fluid? Did you use new fluid or a container that's been in the garage for a while?
Also, was i bled properly ? Master first, then furthest away bleed nipple next etc

**SilverRA23** · 21-10-2011, 08:10 PM

The fact its hard, then fades away while your foot is on the pedal, definitely has all the symptoms of failing master cylinder.

Sometimes they can fail after you do a big brake bleed.. the piston goes past a point that it normally would in every day braking and gets damaged on a rusty surface.

**J0RD0** · 21-10-2011, 09:05 PM

fluid was new, ill pull the master off get it reco'd and see how it goes. I honestly though i would have got i bit more than a couple of years out of it. oh well

**George** · 22-10-2011, 05:17 AM

Is fluid level constant or you can note some degrading?

Even when there's no evident leaks, fluid can still leak into intake manifold thru vacuum hose, indicating m/cyl failure.

**allencr** · 22-10-2011, 03:58 PM

Originally Posted by J0RD0

I honestly though i would have got i bit more than a couple of years out of it.

How was the bore finish & what assembly lube?

**J0RD0** · 24-10-2011, 07:54 PM

word back from clutch n brake place it was leaking, i couldnt even see any fluid leaking. Must have been a bit of crap in the reservoir.

Problem solved, thanks to all who replied.