thomas Boersma

I've got a 93 Maxima SE (non-ABS) with a bit of a brake issue. The brake
pedal feels firm / normal with 2-3 inches free play most of the time, but
sometimes when you go to push the brake pedal, it actuates the master
cylinder at a much lower point (7-8 inches). Sometimes it remains this way
for 10 minutes, sometimes for several days. Outside temperatures and
under-hood temps don't seem to make any difference. When the pedal is low
(or normal for that matter) the brake warning lamp is not lit, it makes no
difference in pedal height or feel if you pump the brakes, and generally,
though low, they don't feel spongy. I've checked for fluid leaks around the
base of the master cylinder, both inside and out, with no leaks. The fluid
level is not reducing, and there is no pulling in any direction nor is there
abnormal wear on the brakes. I've considered that there might be a fault
with the booster, but I've never heard of any kind of work / no-work / work
situation with one of these dual-diaphragm type units. I've checked for
vacuum leaks, and found none in the supply hose. I haven't yet replaced the
check valve, but I seem to be getting a pretty strong vacuum signal even
when it's in one of it's low- pedal moods. I've had master cylinders
internally by-pass on me before with other cars, but they never felt like
this, and never worked sporadically like this. I wonder if there might be a
brake fluid impurity problem, possibly a previous owner using DOT 3 instead
of 4? I know I've seen imports have leak issues with hydraulic clutches
using DOT 3 fluid...

Any insight would be appreciated. All comments appreciated.


Tom
boer9544@bellsouth.net