brake question...hopefully not a repeat

[millertyme]

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I have noticed something strange with my 87 5KT.
The brakes seem to be acting like the bomb is dead (or dying), but I
noticed today that the brake pedal is very hard, but then it acts like
regular power brakes, even if applied repeatedly.
The pedal is hard, but then as I am almost stopped, the pedal gets easy,
and stays that way until I don't use the brakes for awhile.  The brake
pedal feels good, no pulsating.
My question is could it be the proportioning valve at the back causing
this?
I hope this is not a stupid question.
Tia
Brian


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