Intermittent spongy brake cause

[donj51]

I have a strange intermittent spongy brake peddle on my "new" 01 LX470. It freaks me out as the peddle will have no pressure to about 1/4th of the peddle travel, then the pressure has a burst of pressure that pushes the peddle up and to a normal feel with the feel of the start of a hard brake.

The symptom has happened a few times, like a valve was stuck somewhere in the master, and now is a concern. It has also been when the outdoor temp is in the 0-10F range, but that's been the temp the last few weeks.

Anyone have this happen to anyone? Any ideas before diving into a rebuild of the master cylinder?

 

[Malleus]

Just spitballing, but maybe check your vacuum lines first.
...or you may have some trash floating around in the MC reservoir, but that wouldn't seem to correlate to the temperature.

 

[JunkCrzr89]

When’s the last time your brake system was flushed and fresh fluid installed? Brake fluid is hygroscopic, so it absorbs moisture over time, which can cause it to congeal at temps below 32*F.

 

[donj51]

When’s the last time your brake system was flushed and fresh fluid installed? Brake fluid is hygroscopic, so it absorbs moisture over time, which can cause it to congeal at temps below 32*F.

Great point. Since I dont have a date, I will start there.