Hi everyone!

A few months back I bought a 2000 4Runner, 6 cyl 5 speed, with 4WD. Earlier today I used the 4WD for the first time due to 2 inches of snow on an uncleared road. I had it in the L4 position, and as I was driving down a slight hill in 1st or 2nd gear, I went to press on the brake pedal and it was jammed/wouldn't depress. Luckily I was going slow enough that I was able to correct the slight spin-out without the brake, but it sure did give me a scare!

Once I got to the bottom of the hill, the brake started working normally. The same thing happened again two miles later as I was turning into my driveway that has a slight hill. The brake pedal wouldn't depress, but started working again a moment later. This is my third 4Runner, so I have driven with the 4WD engaged before. My previous two were 1st gens, and I even rolled one of them (not on purpose) that happened to have the 4WD engaged. Even though the brakes weren't enough to stop my slide off the road at the time, the brake pedal definitely didn't seize up like I experienced today.

Any insights any of you may have will be greatly appreciated--I just want to make sure that this issue isn't due to user error before I take it into the shop.

Thanks so much and Happy New Year!

 

There is a check valve in the power brake vacuum line near the brake booster.
These are known to freeze up in cold weather.
You can try replacing that and see if it solves the problem.
The part no. might be 44730-60060
It does get your attention when that happens!

 

Brake fluid also has an infinity for water, over time it absorbs water, perhaps a brake fluid bleed/flush will reduce the freeze up aswell if it hasn't been changed in a long time.

 

Thanks for the suggestions Marc and Malcolm99! I'll have my friend check both of them out for me.