On Mon, 15 Dec 2008 13:02:00 -0000, "Mortimer" > wrote:

>"Vic Smith" > wrote in message
.. .
>> On Sun, 14 Dec 2008 21:15:11 -0500, Nate Nagel >
>> wrote:
>>
>>>metspitzer wrote:
>>>> I found some at a relative's house that may be 15 years old.
>>>> It is in a can with a screw off top. I didn't notice the brand.
>>>
>>>If it is a metal can and has an airtight seal, it is probably OK.
>>>However if the seal has been compromised in any way it is likely full of
>>>moisture and only good for paint stripper. Personally I would not use
>>>it. If it has ever been opened and partially used, it is definitely
>>>trash. DOT 3/4 brake fluid is highly hygroscopic, this is why you
>>>should change it every couple of years.
>>>
>> Oh hell, I never touched the brake fluid on my '88 Celebrity in the 14
>> years it was in there.
>> Never had any indication it was affected.
>> Same with my current cars, one a '90 and the other a '97.
>> Never touched the fluid.
>> These are closed systems.
>
>Don't they have a reservoir vessel under the hood with a removable screw top
>where you can check and top up the level as required? I bet that top is not
>100% airtight and will let a small amount of moisture in over the months and
>years. Isn't replacement of the brake fluid something that is done at
>service every few years?
>
>I imagine the same is true of the power-steering fluid (if the car has PAS),
>though the effect of water in the fluid is much less severe than for brakes.
>

I'm sure some will argue the seal, whether the lid is screwed on or
clamped on, isn't 100% effective.
Evil moisture laden air will somehow infiltrate.
I don't buy it.
But I won't argue against changing whatever fluid you want to.
It could be a safety issue.
Just remember that pouring it in the reservoir will expose it to the
evil moisture laden air to a much greater degree than any seal
leakage. Same with even checking it. Hell, when you pull the cap it
starts sucking up water.
All I'll say for sure is I've had many cars for many years and NEVER
changed PS or brake fluid and NEVER had brake problems related to
fluid.
Maybe I'm just a lucky guy.
I will say the way I drive I can count the times I have had to stand
on my brakes in the last 30 years on less than 10 fingers.
They worked fine, with no excessive fade.
Maybe if had more emergency stops it would show up.
I'd like to see a real chemical analysis of old fluid in a normally
sealed master cylinder before I change my habits.
Problem is in the process. Going by what you hear from the
moisturephobes, just opening the lid will have it sucking up water
from the air, nullifying any lab results.
The reservoir seals I see on the GM cars I've had don't look like
they'll let any air in, and that's been good enough for me.
If anybody thought critically about this, they'd just put some air
pressure on a removed cylinder and see if there's leakage through
the cap. I'll bet they're good for a couple PSI, more than they'll
ever get from the outside.

--Vic


--Vic