Very cold, NO BRAKES

[DAS]

On my car it is not a loss of power assist issue. Fwiw I have also changed the brake fluid, so I doubt that is the issue.
In ten years and 196,000 miles this issue has presented maybe a dozen times.

[mikec]

I have had a problem with the check valve sticking on an '95. The problem was not water freezing in the check valve. Sometimes the check valve would just stick nearly shut, but would free up after 30 sec or so after starting. I have the old check valve in my hand right now. It looks to cost maybe 30 cents, so it's really cheaply constructed.

So, even if you don't think that it is the problem, just replace it anyway!

ps the check valve is in hose from the vacuum assist to the intake manifold.

[ring-tailed-lemur]

Thanks again for the feedback, everyone! You guys are seriously awesome. Hopefully I'll be able to solve this, at least for awhile.

This morning, my wife went out and started the car beforehand and let it run for about 5-10 minutes before leaving. She said that she pumped the brakes about 10 times as well, and it didn't happen when she left. It was about 15 degrees (F) out.

[D Forrest]

Originally Posted by DAS

On my car it is not a loss of power assist issue. Fwiw I have also changed the brake fluid, so I doubt that is the issue.
In ten years and 196,000 miles this issue has presented maybe a dozen times.

How can you tell it it is not a loss of power assist issue?

[DAS]

No brakes.

[5outbacks4jon]

Freezing condensation in the brake fluid?

[canubaru]

If there is a tear in the booster diaphram, it can pull in moisture.

cardoc,

what other symptoms would this cause besides contributing to the frozen check valve issue.?

thanks

[jp1203]

Happens to me when it's really cold...not no brakes, but I barely have brakes. I think it's what Nipper is saying where I actually lose power brakes. Usually about two stops and they're back to normal. I tend to forget about it all summer but it comes back on the coldest days in the winter. Unless it starts happening more frequently, it doesn't bother me all that much.

[jp1203]

Originally Posted by D Forrest

How can you tell it it is not a loss of power assist issue?

In my case, I'm pretty sure it is a loss of power assist issue since I forgot to reconnect the vacuum line to the brake booster on my sister's Legacy once. Took it for a ride...little bit scary to say the least since I wasn't expecting that! When my '04 has this issue in the cold, the brakes feel very much like that.

Not sure if I'd recommend doing that, but it could be one way to tell.

[cardoc]

Originally Posted by canubaru

cardoc,

what other symptoms would this cause besides contributing to the frozen check valve issue.?

thanks

Its a vacuum leak. It can cause P0170/171 or P0420 if it allows enough air through. Sometimes there can be a leak in the diaphram and it will only be opened enough to allow air in at the time the booster is activated by brake pedal pressure and not be apparent when the booster is inactive.

I have changed a few boosters with a leak that caused a 420 or lean codes on different vehicles. I would be watching the scanner data and all would look good until I pushed the brake, then, a quick rise to a lean value from the AF and engine tone changes. I've also had them fail to the point that I could hear it sucking in air from under the dash. Didn't need a scan tool for that.