35 replies to this topic

[nipper]

Have not done the brake booster test yet. It's on my things-to-do list.

This is one of those problems that, when it shows up, the conditions are not very conducive to troubleshooting (20 deg in the morning). When the weather is more friendly, like in the spring and fall, the problem is not there.

hrmmm do you have a long hill by your house thsts straight and safe to try a test on?
With the car off pump the barkes 10-15 times. With your foot on the brake pedal start the car, the pedal should move to the floor. If it doesnt you have a bad booster. Do this test first thing in the morning when the car usually has no brakes.
After doing the booster tests (test takes 5 minutes so no excuse for NOT doing it). Park the car in neutral using the hand brake. Pump the brake 10-15 times. With the engine off, but the ignition switch in the unlock postion release the hand brake. once the car starts rolling a bit, press the brake pedal. does the car feel the same? You can start the car in neutral rolling then get brakes back. Remeber when you loose pwr steering and pwr brakes, you can still control the car, but it takes a lot more force to do it.
My gut feeling is that the car is not loosing brakes, but loosing the booster vaccum. Once the booster builds up vaccum its fine. I bet a pinhole leak is in the booster diaphram. The car WILL stop, but you may need alot of force or two feet to do it when it feels like you have no brakes.

nipper

[srs_49]

Here's an update on the problem. My wife pulls into the driveway back in July and all kinds of smoke is coming out from under the front wheelwells. Looked like the front brakes were not releasing after being applied and were just dragging on the rotors. After letting things cool down (this took quite a while), I tried the car and lo-and-behold, no brakes at all (well, maybe a little bit, but not much). Tried bleeding the brake lines, but could never build up any brake pressure in the front (right front, specifically). So, I replaced the master cylinder, re-bled all 4 wheels, and this fixed the problem.

It will be interesting to what happens this winter. If the original problem reported (brakes not working when cold) does not surface, then I would assume the problem was in the master cylinder.

Will keep this thread updated with the results.

[srs_49]

As promised, here's an update to the thread. I mentioned previously that I replaced the brake master cylinder back in July '06. The winter weather around here (central Maryland) has been very mild up until a week or two ago, so it wasn't until last week that temperatures dropped into the relm where the problem shows up (below freezing).

Well, the brakes still don't work after an all night soak in 20 deg or lower weather. The problem is still there, maybe even getting worse since my wife says it takes here a couple of tries to get the brakes working before she leaves the driveway. Symptoms are the same as it has always been - feels like something is keeping the brake pedal from depressing. There's absolutely no feel to the brakes at all when this occurs, and, no braking (or very little). So, the problem is almost definitely not in the master cylinder. I guess the next place to look is the vacuum boost, which some of the posters here have suggested.

Stay tuned

[Petersubaru]

my recently purchased '01 had only $20 napa organic pads in the front,,...enough to pass the mechanical safety for the used car dealer .. when the temp gets to around freezing, they would barely stop until warmed up after sometime ...but even after warming up they were very poor compared to the other cars I also drive...at the moment I am waiting for another set of pads...

My wife's 2002 Outback's (LL Bean) brakes sometimes don't work when the car is started, either first thing in the morning when leaving for work or, less frequently, in the afternoon after a cold soak on the parking lot. First time it happened, ended up the neighbor across the street's driveway. Symptom is like the power assist has failed (no vacuum boost?). Car can be stopped by really standing on the brake pedal. Problem only shows up when outside temperature is below approx. 25 deg F. After 1 or 2 minutes of either idling or slow driving, problem clears up and car is fine for rest of drive. Also, through experimentation (it's been below freezing all week), found that pumping the brakes really hard several times when car is first started seems to get things working. Anyone else have similar probelms?

[nipper]

It must be contagous.

Usually i use the remote starter to warm the car then take off. Today i was too far from the car to do that at my freinds house. It was 22 outside.
I went to make a 3 pt turn, and Blu's (97 obw 202K)brake pedal was hard as a rock and took two (human) feet to stop. AFter i backed up, it was fine.

I'll have to see if it does it again

nipper

[srs_49]

I tried Nipper's brake booster test this morning (4:30AM). Outside temp was 20 deg F.

"hrmmm do you have a long hill by your house thsts straight and safe to try a test on?
With the car off pump the barkes 10-15 times. With your foot on the brake pedal start the car, the pedal should move to the floor. If it doesnt you have a bad booster. Do this test first thing in the morning when the car usually has no brakes."

The brakes reacted just as he decribed. Hard as a rock when first pumped up with engine off, then still hard (no braking,or very little) when engine first turned on. After maybe 10 secs of really standing on the pedal and the engine running, could feel the booster kick in, the pedal moved down a bit, and I had the normal braking (started down the driveway to confirm).

My next step is the vacuum power boost or the one way valve in the vacuum line someone else suggested.

[srs_49]

It must be contagous.

Usually i use the remote starter to warm the car then take off. Today i was too far from the car to do that at my freinds house. It was 22 outside.
I went to make a 3 pt turn, and Blu's (97 obw 202K)brake pedal was hard as a rock and took two (human) feet to stop. AFter i backed up, it was fine.

I'll have to see if it does it again

nipper

Yep, that's the exact problem/symptom I've been having. See my latest 2 posts.

[nipper]

I tried Nipper's brake booster test this morning (4:30AM). Outside temp was 20 deg F.

"hrmmm do you have a long hill by your house thsts straight and safe to try a test on?
With the car off pump the barkes 10-15 times. With your foot on the brake pedal start the car, the pedal should move to the floor. If it doesnt you have a bad booster. Do this test first thing in the morning when the car usually has no brakes."

The brakes reacted just as he decribed. Hard as a rock when first pumped up with engine off, then still hard (no braking,or very little) when engine first turned on. After maybe 10 secs of really standing on the pedal and the engine running, could feel the booster kick in, the pedal moved down a bit, and I had the normal braking (started down the driveway to confirm).

My next step is the vacuum power boost or the one way valve in the vacuum line someone else suggested.

when in doubt, start cheap. Go for the valve first.

nipper

[nipper]

im wondering if there is some condensation freezing in the booster due to a bad check valve.


at 202,000 miles i wouldnt begrudge my car a check valve failure.


nipper

[srs_49]

im wondering if there is some condensation freezing in the booster due to a bad check valve.


at 202,000 miles i wouldnt begrudge my car a check valve failure.


nipper

I'm going to try the check valve this weekend (see the other thread about this same topic). Luckily, it's supposed to remain cold for the next week or so, so should be a good time to troubleshoot. In the past, as soon as I would try something, the weather would warm up and the problem only occurs below freezing.

[srs_49]

:)Success! On Nipper's suggestion, I removed the vacuum hose assy between the brake booster and the intake manifold. The check valve is embedded in the hose, so it's not something you can remove separately and replaced. It did appear to be sticking a bit (the old suck test), so I cleaned it with carb cleaner and dried it out with compressed air. The past 2 mornings, when the temperature was 10 deg F (yesterday) and 8 deg F (this morning), no problem at all! Had good brakes from the moment the engine started. Problem solved, at least for now! Though the car was in the garage those past two nights, the garage is unheated so it's, at best, only a couple of degrees warmer than the outside.

I'm not sure if this fix would solve everyone's problems, but you sure can't beat the price ($0). I'll probably buy another hose/check valve assy to have around in case the problem resurfaces.

Thanks for all the suggestions. This problem has been hanging around for over 3 (4?) years. I brought it up to the dealer's attention when the car was still under warranty, but they did nothing because they claim they could not duplicate the problem.

If anything changes, or if the problem comes back, I will post an update.

BTW, there's another thread on this forum started by OswaldtheBold about this same problem.
http://www.ultimates...ead.php?t=70543