hard brake pedal no power assist when cold

[Climber2377]

for a couple of years now i have had the same problem when the weather turns bitter cold. my brake pedal gets hard when i first start the car when it is below freezing out. it will stay hard and the car will not stop well until i pump the pedal till i feel the power assist helping as the pedal will soften back up. has anyone else ever had this problem? i have lived with it, and it doesnt bother me unless i have to go someplace. sometimes it takes about 30 seconds to a minute to get the pedal back. just curious if anyone else has had this happen to them... and if they did, is there a solution? thanks in advance

[RobLog]

There is a check valve in the brake vacuum hose to the booster that can freeze closed in cold weather. See the thread referenced below for more info.

Frozen check valve in brake booster vacuum line

[Heffernan]

I had this happen to me for the first time today. Scared the **** out of me..almost caused an accident.

[Climber2377]

sweet... all this time and all i had to do was write a post and get some wd40! sweet! thanks

[nipper]

Sometimes you need to replace that hose, with check valve in it.

[Climber2377]

fair enough. i ll try to get to it today or tomorrow as it will be warmer here. first the wd, if it doesnt do the job, i might just leave it, i ve lived with it this long. just over 242k now

[mikec]

I'd replace the hose with the check valve. My 95 had the same symptoms. when I cleaned the hose and check valve, it would work OK for a couple of weeks and then reaccure. After I replaced them, I cut out the check valve. It was clean and I couldn't see any reason why it was sticking shut.

[wilsonhp]

It was sticking shut because of water in the line, from the manifold. The water freezes, locking the valve.

I had this happen twice last week. I predicted it was going to happen both times, and was prepared. If the conditions are right for it to happen (below zero), then just make sure you pump your brakes a few times until the pedal softens BEFORE you start off moving. The first pump will seem OK, the second rock hard, and about the third or fourth time, the pedal will soften again. You might have to pump it HARD to free the valve, so don't be afraid to press hard. Once it's loosened, it stays that way until it freezes again.

The WD-40 will flush out the water and it will work until significant water makes it's way back to the valve again.

Replacing the hose won't make it work any better, maybe just take a bit longer until sufficient water gets in to make it happen again.

[cardoc]

It pulls air in through the booster side. Moisture in the booster gets sucked into the valve. Moisture gets into the booster through pours in the booster system.

[CNY_Dave]

Does the booster pull air from the engine compartment or the passenger compartment?

Is it indicative of a leaky booster?