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Cold weather brake problems


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74 replies to this topic

#51 grossgary

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Posted 06 February 2007 - 01:34 PM

digital thermometer read -8 degrees this morning so i did something i normally don't do - i warmed the car up. brakes worked fine, i guess warming up freed the valve. i will wait until warmer weather to check into it. this is in my XT6, old gen but possibly same issue.

#52 nipper

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Posted 06 February 2007 - 02:34 PM

digital thermometer read -8 degrees this morning so i did something i normally don't do - i warmed the car up. brakes worked fine, i guess warming up freed the valve. i will wait until warmer weather to check into it. this is in my XT6, old gen but possibly same issue.


i love my remote starter


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#53 OswaldtheBold

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Posted 06 February 2007 - 08:38 PM

http://auto.howstuff...ower-brake2.htm


OK i see freezing as the cause. One side of the booster is exposed to moist cabin air, the other side to dry outside cold air. You Get this mix you get condensation. When the air is cold enough that condensatiuon freezes. Check valve doesnt have anything to do with it.

When it is below 35 the AC in the car does not work, so there is no way to dry out the air.

http://sg.answers.ya...02205101AAz5pfN

I just searched the net and i come up with an unsatisfactory answer (flush the brakes). In that one article that stated that, the respondont just did a flush the year before. (he had a 2000 subaru).

Now there arew two failure modes. The one with the bad master cylinder, the pedal goes to the floor. The freezing Power Brake booster, you get a very hard pedal.
best i can tell is that we all need pwer brake boosters (im not sold on that). If there is no recorgnized problem, then there is no solution.

For now, DO NOT DRIVE BELOW 30 DEGREES UNTILL YOU HAVE A BRAKE PEDAL!

nipper

At least in my case, I don't think the problem is moisture in the brake booster. I had the booster replaced with a new one, and the problem was essentially unchanged. I consider it unlikely both the old and the replacement boosters were exposed to conditions sufficiently similar to cause the same problems, while my other '97 Legacy parked next to it has never had this problem.
I am leaning towards the check valve theory, but haven't had the chance to try it yet.
Anybody know the cost of a replacement valve and hose from Subaru?

#54 cookie

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Posted 06 February 2007 - 08:52 PM

I bet we will know soon. Sounds like good maintenence for all of us.

#55 uniberp

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Posted 07 February 2007 - 11:14 AM

I'm way late into this, but did anyone mention that older engines pull less vacuum?

Qeustion: does an engine pull less vacuum at didel in extereme extreme cold temps due to increased air density?


I bet we will know soon. Sounds like good maintenence for all of us.



#56 nipper

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Posted 07 February 2007 - 11:38 AM

I'm way late into this, but did anyone mention that older engines pull less vacuum?

Qeustion: does an engine pull less vacuum at didel in extereme extreme cold temps due to increased air density?


It shouldnt. It may pull less vaccum cause of high idle, but thats a a result of the engine temp not air density. You get into air density with altitude, not so much temperiture. Remeber this is an artic front, look at the barometer, you will se its reading high pressure, same as a summer day.

nipper

#57 LosDiosDeVerde86

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Posted 07 February 2007 - 12:30 PM

master cylinder or a frozen brake system (extreemly rare). There was a test for the Pwr brakes, but since you replaced that its the master cylinder.

nipper

nipper


i havn't read all the posts and this quite possibly could be a re-post:

i had the same problem. got a brake flush and bleed and all was fine. i woke up yesterday here in Pittsburgh and it was -8 and the breaks worked perfectly.... the struts however seemed frozen and the entire ride to work felt like i was in a WWII Military Jeep.

#58 uniberp

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Posted 08 February 2007 - 11:47 AM

It shouldnt. It may pull less vaccum cause of high idle, but thats a a result of the engine temp not air density. You get into air density with altitude, not so much temperiture. Remeber this is an artic front, look at the barometer, you will se its reading high pressure, same as a summer day.

nipper


If compression is lower, by say 10%, wouldn't vacuum be lower? I never checked compression on my 2 (97 2.2 and 99 2.5PII), so IDK about degrade rates.

#59 nipper

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Posted 08 February 2007 - 02:19 PM

If compression is lower, by say 10%, wouldn't vacuum be lower? I never checked compression on my 2 (97 2.2 and 99 2.5PII), so IDK about degrade rates.


Not really. 10% is nothing, and you really cant go by percentages, you need raw numbers. YOu can have one cylnder at 180 and another at 160 psi and still be acceptable (mathmatically it should be an 18 psi differnce but most gauges dont have markings that are readable that fine).

A vaccume gauge is more dependent on valve timing, a "hot" cam will have a lower a vacum then a stock cam, but that doesnt mean anything is wrong with the car.
What the vacum gauge will tell you about your engine is if the needle is bouncing around at idle. In fact a vacume gauge can be muchh more informtaive then a compression tester when your first looking for the source of a problem. This isnt mine, but it explains it better then me doing alot of typing:


Diagnosing car engines with a vacuum gauge. A vacuum gauge gives
a quick and cheap (under $15) indication of engine problems. To
isolate a problem further diagnostics are usually needed.

This is a consolidation of diagnostics from three sources:
1. instructions for Equus vacuum gauge
2. Chilton general car care manual
3. Haynes emissions control manual

Connecting the vacuum gauge.
Engine must be warm or the gauge reading will be too high and
computer will be in warmup mode. Select a vacuum hose connected
directly to the car's intake manifold or select an unused port on
the manifold. The best alternative would be to attach a hose to
an unused port on the manifold and leave it there for use with
the gauge. Plug the hose when not in use. Otherwise if in doubt
which hoses are connected to the intake manifold, consult the
hose diagram on the emissions sticker, usually found on the
underside of the hood or on the firewall, or consult a repair
manual. If still in doubt the hose to the MAP (pressure) sensor
is connected directly to the intake manifold. The gauge can be
tapped into a hose using a T-connector. For a quick and dirty
reading unplug the easy to find PCV hose on the valve cover and
plug in the vacuum gauge. Using the PCV hose may not give a
direct connection to the intake manifold and it will cause the
engine to idle slowly, but it will give an intake vacuum reading
and is easy to use when looking at a strange car, for example a
prospective purchase. Start the engine and read the gauge in
inches of mercury (in Hg). The dial on the gauge may be marked
with the good range.

1. Equus instructions
a. testing at idle speed
- compare vacuum reading with manufacturer's specification.
- a lower reading indicates possible incorrect timing,
incorrect valve timing or adjustment, incorrect setting of
idle mixture, worn piston rings, or leak in intake
manifold.
- readings that change slowly indicate incorrect setting of
idle mixture screw.
- readings that change quickly indicate sticky valve guides,
burned valve sets, or leak in head gasket.
b. testing at 2000 rpm
- a lower reading indicates possible restriction in exhaust.
- oscillating reading indicates possible weak valve springs.

2. Chilton general car care manual.
- gauge reading steady 17-22 in Hg indicates normal engine in
good condition.
- gauge reading low (15-20 in Hg) but steady indicates late
ignition or valve timing, low compression, stuck throttle
valve, leaking carburetor or manifold gasket.
- gauge reading steady but dropping regularly indicates burnt
valve or improper valve clearance.
- gauge reading dropping gradually at idle indicates choked
muffler or obstruction in exhaust.
- gauge reading slowly dropping to zero as engine speeds up
indicates choked muffler.
- gauge reading fluctuating between 15 and 20 in Hg at idle
indicates stuck valve or ignition miss.
- gauge reading drifting indicates improper carburetor
adjustment or minor intake leak at carburetor or manifold.
- gauge reading fluctuating as engine speed increases
indicates weak valve springs, worn valve stem guides.
- gauge reading vibrating excessively at idle but steady as
engine speeds up indicates worn valve guides.
- gauge reading vibrating excessively at all speeds indicates
leaky cylinder head gasket.
3. Haynes emissions control manual
a. testing at various speeds
- engine starting vacuum should be 1 to 4 in Hg. To test
disable ignition (ground wire from coil), hold throttle
wide open, crank engine slowly with starting motor.
- healthy engine at idle should read steady 15 to 20 in Hg.
- healthy engine at 2000 rpm should read steady 19 to 21 in
Hg.
- healthy engine at open throttle should read close to 0 in
Hg.
- healthy decelerating engine reading should jump to 21 to
27 in Hg as open throttle released.
b. testing at idle speed
- low steady reading usually indicates leaking gasket
between intake manifold and carburetor or throttle body,
leaky vacuum hose, or incorrect camshaft timing.
- low fluctuating (3 to 8 in Hg below normal) reading may
indicate intake manifold gasket leak at an intake port or
faulty injectors on port-injected engines.
- regular drops (2 to 4 in Hg) in reading at a steady rate
indicates probable leaking valves.
- irregular drops in reading indicates possible sticking
valve or ignition misfire.
- rapid vibration (4 in Hg) in reading combined with exhaust
smoke indicates worn valve guides.
- slight fluctuation (1 in Hg) in reading indicates possible
ignition problems.
- large fluctuation (10 in Hg) in reading indicates likely
weak or dead cylinder or blown head gasket.
- slow movement through wide range in reading indicates
possible clogged PCV system, incorrect idle fuel mixture,
or gasket leak between carburetor, throttle body, or
intake manifold.
c. testing at higher speeds
- rapid vibration (4 in Hg) in reading at increased engine
speed indicates leaking intake manifold gasket or head
gasket, weak valve springs, burned valves, or ignition
misfire.
- reading returns slowly to normal and didn't peak above
normal (5 in Hg) after dropping to zero when throttle
quickly snapped open (2500 rpm) suspect worn rings.
- reading returns to normal after long delay when throttle
quickly snapped open (2500 rpm) suspect blocked exhaust.
d. testing for blocked exhaust
- idle speed reading slowly dropping toward zero indicates
exhaust restriction.
- excessive backpressure in exhaust then indicated by
reading not increasing quickly to about 16 in Hg when
engine speed slowly increased to 2000 rpm.
- backpressure also indicated by reading not dropping as
quickly when throttle quickly released and remaining 5 in
Hg higher or more than normal.
- disconnect exhaust manifold from engine and retest. If
problem disappears exhaust system is blocked.
- to locate restriction reconnect exhaust system one unit at
a time testing after each until problem reappears.


nipper

#60 srs_49

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Posted 20 February 2007 - 01:11 PM

:banana: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.


Just an update. It's been 2 weeks since I cleaned out the vacuum line with the check valve. Nightime temperatures have been consistently in the teens, and this past weekend we were up in the mountains where the nightime lows were in the single digits. The brakes have been working fine - no problems at all when the car is first turned on (or at any other time). I highly recommend trying this fix.

#61 yohy

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Posted 20 February 2007 - 02:39 PM

On my '97 LL, I pulled the line off the car and did the same "suck test" as described by srs_49. As the valve appeared to working correctly, I decided not to introduce any chemicals but rather just compressed air. Put it back on the car and in the last week with temps still at or below -0- at night, the brakes have been fine, no issues at all on start up. As mentioned, for a fix that takes 10 minutes and costs zero dollars, you can't beat it.

#62 nipper

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Posted 20 February 2007 - 09:01 PM

As mentioned, for a fix that takes 10 minutes and costs zero dollars, you can't beat it.


Except your way i have to go out and buy an air compressor..
:-p


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#63 yohy

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Posted 20 February 2007 - 10:13 PM

unless you have a good set of lungs!

#64 srs_49

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Posted 21 February 2007 - 06:58 AM

Except your way i have to go out and buy an air compressor..
:-p


nipper


Heck, use the opportunity as an excuse to buy a new tool! Usually works for me (though I got my air compressor as a gift - sure beat getting a tie!).
;)

#65 Reveeen

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Posted 21 February 2007 - 08:46 AM

I have noticed that when cold (-20) my Legacy does not generate more than 13 inches of vacuum when cold, it's fine (20) when warm, maybe this is what you are seeing? (or feeling the result of?) and of course, being turbocharged, if driven cold there sure isn't a lot of vacuum availaible to make the booster work, at least for the first little bit.

#66 Audiophobe

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Posted 25 February 2007 - 06:43 AM

If this is such a common and dangerous problem, isn't this cause for a recall?
I've seen recalls for things less important than this.

#67 nipper

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Posted 25 February 2007 - 09:26 AM

If this is such a common and dangerous problem, isn't this cause for a recall?
I've seen recalls for things less important than this.


So far this is being seen on cars with over 100K, and at that mileage, its no longer considered a design defect, but just a part failing.
If people under 100K have this problem, they need to report it to the NHTSA.

nipper

#68 johnceggleston

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Posted 25 February 2007 - 12:46 PM

regarding the cleaning/blowing out of the check valve, would there be any benift in using an alcohol or similar spray to absorb the moisture? wouldn't blowing it out by mouth re-introduce moisture into the valve?

any chance this problem, in part, is based on the conditions when you turn off, last used, the the car? and/or is there a good/better cold weather lubricant that might benifit the valve operation?

just wondering.

#69 nipper

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Posted 25 February 2007 - 03:29 PM

I dont think its humidity as much as dirt mixed with gunk and himidity.

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#70 srs_49

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Posted 26 February 2007 - 07:07 AM

regarding the cleaning/blowing out of the check valve, would there be any benift in using an alcohol or similar spray to absorb the moisture? wouldn't blowing it out by mouth re-introduce moisture into the valve?

any chance this problem, in part, is based on the conditions when you turn off, last used, the the car? and/or is there a good/better cold weather lubricant that might benifit the valve operation?

just wondering.


I used an air compressor. While there's no air drier, the air coming out is probably less moist than what comes out of someone's mouth. I also ran some carb cleaner through the hose/valve before drying it, so if there was any "gunk" there, the cleaner should have taken care of it.

#71 srs_49

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Posted 26 February 2007 - 07:15 AM

So far this is being seen on cars with over 100K, and at that mileage, its no longer considered a design defect, but just a part failing.
If people under 100K have this problem, they need to report it to the NHTSA.

nipper


I first experienced this problem when the car was less than 2 years old and only had ~40K miles on it, so it's not strictly a high-mileage problem. I took it back to the dealer, but, they were unable to repair. Given the specific conditions under which the problem occured, that's not surprising, even given my dealer's service dept incompentencies. I'm sure had I taken it back out of warranty, they would have been more then willing to replace the master cylinder, power boost assy, and who know what else, until they finally "shotgunned" enough parts that they eventually got around to the hose/check valve.

Yes, I did report the problem to the NHTSA, 2 or 3 years ago. Have never heard anything.:-\

#72 Audiophobe

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Posted 26 February 2007 - 10:18 AM

So far this is being seen on cars with over 100K, and at that mileage, its no longer considered a design defect, but just a part failing.
If people under 100K have this problem, they need to report it to the NHTSA.

nipper


You may know more than me but I doubt that milage is relavant to recalls. My car is a 2001. Would it matter if it has 150k or 50k on it? I would think the model year would be more relavant.

#73 nipper

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Posted 26 February 2007 - 10:26 AM

You may know more than me but I doubt that milage is relavant to recalls. My car is a 2001. Would it matter if it has 150k or 50k on it? I would think the model year would be more relavant.


mileage is very revelant. Things break things wear out. for example if a new car gest sitcky calipers at 20,000 miles thats one thing, if they get it 120,000 miles thats something else. Things bust with time, its just that there is a pattern here. Every car as it gets old develops a pattern of failures with mileage. Thats because they are mass manufactured.
If a model of car starts having master cylinder failures afer 130K, thats just wear and tear, otherwise these things can go on for ever and it really isnt fair to the mfg. Whats next, my frame rotted out at 160,000 miles os its the mfg fault. It doesnt and cant work that way, so its just something we ned to be aware of.

nipper

#74 mcgw1000

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Posted 23 March 2007 - 05:08 PM

I experience the same problem on my 97 OBW. I was planning on bleeding/fushing the barke lines when things slow down a little but i did have an oppurtunity to remove the vacuum hose and blow it out last weekend. I pulled the car in the garage when I got home around 6PM on Friday (it was snow and ice covered). I did not get to it till afternoon on Saturday and when I pulled the vacuum lines, the diaphram was still holding vauum (evidenced by the whosh).

Does anyone have any updates?

#75 nipper

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Posted 23 March 2007 - 05:11 PM


Does anyone have any updates?


Spring :-p

(warmer weather)

nipper




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