Cherokee 180 soft brake - causes?

"Dave Stadt" writes:

Wow; I'm surprised.... I'd think oil would absorb air far too easily.
That's SURE to cause spongy brakes...

I've never seen or heard of oil absorbing air.

Well, overfill a crankcase and watch the oil get whipped into a
froth, and rapidly lose its lubrication qualities...

Automotive brake fluid was, ISTM, the very first federal
automotive safety standard. It must have:

High boiling point
low air absorbation
compatability with rubber lines and seals

There were a few cars, but VERY few, that needed non-standard brake
fluid. One was a friend's Hillman Minx (Mynx?) that Goodyear or
Firestone or such had put DOT-3 in; every seal was gone. The other
was the Citroen DS with master hydraulic pump that ran brakes,
steering, suspension and transmission. It used exotic "green blood"
and every owner carried a spare 10 litres or so...just in case...




--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

"David Lesher" wrote in message
...
"Dave Stadt" writes:

Wow; I'm surprised.... I'd think oil would absorb air far too easily.
That's SURE to cause spongy brakes...

I've never seen or heard of oil absorbing air.

Well, overfill a crankcase and watch the oil get whipped into a
froth, and rapidly lose its lubrication qualities...

That's not exactly what could happen in a brake circuit. We are talking
brake circuits not crankcase. Leave oil exposed to the atmosphere and it
does not absorb air.

Automotive brake fluid was, ISTM, the very first federal
automotive safety standard. It must have:

Traditional automotive brake fluid is alcohol based and is hydroscopic. A
can will become useless in a matter of hours if not tightly capped. It is
not oil based.

High boiling point
low air absorbation
compatability with rubber lines and seals

There were a few cars, but VERY few, that needed non-standard brake
fluid. One was a friend's Hillman Minx (Mynx?) that Goodyear or
Firestone or such had put DOT-3 in; every seal was gone. The other
was the Citroen DS with master hydraulic pump that ran brakes,
steering, suspension and transmission. It used exotic "green blood"
and every owner carried a spare 10 litres or so...just in case...

Anybody that drove or drives a Citroen needs more than 10 litres of green
blood. A Priest, a tow truck and a credit card with no limit is a good
place to start.

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

"Dave Stadt" writes:


That's not exactly what could happen in a brake circuit. We are talking
brake circuits not crankcase. Leave oil exposed to the atmosphere and it
does not absorb air.

Nope, just water..... but in any case the key issue is having a
fluid that has very low compressibility even at high temperatures.
(Look at the NOVA series on the 777; the rejected-takeoff test has
the solid carbon rotors glowiing bright orange as the rims melt...now
THAT'S hot....). Even a small amount of suspended air makes it
compressable. And oil, unlike brake fluid, does not err ?stratify?
well.

Automotive brake fluid was, ISTM, the very first federal
automotive safety standard. It must have:

Traditional automotive brake fluid is alcohol based and is hydroscopic. A
can will become useless in a matter of hours if not tightly capped. It is
not oil based.

Ahem.. it's not alcohol-based; it's glycol based. (Except DOT-5 which is silicon..)


High boiling point
low air absorbation
compatability with rubber lines and seals

Anybody that drove or drives a Citroen needs more than 10 litres of green
blood. A Priest, a tow truck and a credit card with no limit is a good
place to start.

Not at all; you merely need 2 tools: a cell phone and a pickup
w/trailer. Just like any MG/Jag owner...

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

"David Lesher" wrote in message
...
"Dave Stadt" writes:


That's not exactly what could happen in a brake circuit. We are talking
brake circuits not crankcase. Leave oil exposed to the atmosphere and it
does not absorb air.

Nope, just water..... but in any case the key issue is having a
fluid that has very low compressibility even at high temperatures.
(Look at the NOVA series on the 777; the rejected-takeoff test has
the solid carbon rotors glowiing bright orange as the rims melt...now
THAT'S hot....). Even a small amount of suspended air makes it
compressable. And oil, unlike brake fluid, does not err ?stratify?
well.

Automotive brake fluid was, ISTM, the very first federal
automotive safety standard. It must have:

Traditional automotive brake fluid is alcohol based and is hydroscopic. A
can will become useless in a matter of hours if not tightly capped. It is
not oil based.

Ahem.. it's not alcohol-based; it's glycol based. (Except DOT-5 which is
silicon..)

Ahem..glycol is.....well why don't you look it up.

"Dave Stadt" writes:


Ahem.. it's not alcohol-based; it's glycol based. (Except DOT-5 which is
silicon..)

Ahem..glycol is.....well why don't you look it up.

Could be, I'm no chemist (and got a C in the subject to prove it...).
But everything I've read on it describes it as glycol. The other
one most of us think of is anti-freeze. Time was, that was
alcohol...well, it used to be it evaporated regularly.

To solve that {and corrostion issues...} Ethylene glycol as "permanent
antifreeze" came on the scene in the 1950's/60's. If that's an
alcohol, then I've learned something new. It sure doesn't burn like
one...



--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

David Lesher wrote:
"Dave Stadt" writes:



Ahem.. it's not alcohol-based; it's glycol based. (Except DOT-5 which is
silicon..)


Ahem..glycol is.....well why don't you look it up.


Could be, I'm no chemist (and got a C in the subject to prove it...).
But everything I've read on it describes it as glycol. The other
one most of us think of is anti-freeze. Time was, that was
alcohol...well, it used to be it evaporated regularly.

To solve that {and corrostion issues...} Ethylene glycol as "permanent
antifreeze" came on the scene in the 1950's/60's. If that's an
alcohol, then I've learned something new. It sure doesn't burn like
one...

A hint: glycols are two-valued alcohols (two hydroxyl groups).

--

Tauno Voipio
tauno voipio (at) iki fi