LexusPia

My 2000 GS4 has only 37000 miles but as of last month after parking in our garage for a long 3-week vacation, the brake light suddenly came on during normal braking which really surprised me. The weather was cold when that happened. Light disappeared soon after the brake was released. However each time the brake is applied, the light comes on. When the weather warms up, the brake light never comes on. Since the temp dipped down to minus 5F last night, the brake light came back on this morning when I took the car out. I noticed when the brake light came on, the brakes required more effort to stop. Based on that experience and what I've read in this forum, I'm just assuming one of the two power boosters for the brakes has failed or in the midst of failing. What are your thoughts on that? Since the car has so low miles, I just find it hard to believe something like that (failed power boosters) can happen. My wife's 1994 ES300 with over 150k is still running great.

jsl55

check the brake fluid level.

BigGene

Aye, make sure fluid is filled to the marked line.

Sounds like your short a bit of fluid, and in the morning when it's cold the light will activate, but later in the day the brake fluid gets warm and expands.

LexusPia

You guys are right on. The brake fluid was about 1/2" below max line. Brake light never came back on after filling the reservoir to the max line. What would cause the fluid level to go down since the brake system is totally sealed? Thanks.

BCP43002

The fluid is drawn into your brake system as your pads wear. Check your pads to see if they are within spec. At 37k it may be time to replace your fronts if original.