R
rogtwo@aol.com
Guest
OK, here I go causing trouble again. Well, I don't mean to cause trouble,
but that's what often seems to happen -- sorry.
First the disclaimer -- I'm no expert on brake fluid, so what I say below is
mostly speculation based on the little I know about grease.
In the aircraft industry, there is some disagreement about whether it's
better to have hygroscopic grease (ones that ABSORB water) or hydrophobic
grease (ones that REPEL water). The argument boils down to this: If the
grease is hydrophobic, then any water that gets in will sit in little drops
and possible cause significant corrosion right where the drops sit. If the
grease can absorb the water (is hygroscopic), then any water that gets in is
absorbed and distributed throughout the grease, thus eliminating the drops of
water that can cause excessive corrosion. Of course, the grease is now damp,
and may cause corrosion over a larger area. This is why there is
disagreement about which is better -- drops of water in limited locations, or
having the water diluted in the grease. Obviously hygroscopic grease should
only be used in a well sealed environment where it won't be absorbing water
out of the air.
So, now to brake fluid. Since the brake system is well sealed, hygroscopic
brake fluid (e.g., DOT 3), MAY be advantageous. That is, if a tinny bit of
water gets past the wheel cylinder seals when you are swimming, this water
will be absorbed into the fluid. This MAY be less corrosive to your wheel
cylinders than having the water sit as a drop in the bottom of the wheel
cylinder as would happen with a hydrophobic brake fluid (DOT 5).
I really don't know which is better, but in either case it's a good idea to
bleed all the 4 wheels regularly (like yearly). Personally, I'm not going to
bother to switch to DOT 5.
Roger St. John
White '63
Seattle
PS - There is no need to start with clean fluid in your bleeder jar. There
is no way that you are going to suck fluid all the way up your bleeder hose
from the bleeder jar. That is, all the fluid (if any) that gets sucked back
in through the bleeder screw is going to be the dirty fluid (that just came
out of the wheel cylinder) that is still in your bleeder hose. The clean
fluid in the jar isn't going to get near the wheel cylinder.
[Non-text portions of this message have been removed]
but that's what often seems to happen -- sorry.
First the disclaimer -- I'm no expert on brake fluid, so what I say below is
mostly speculation based on the little I know about grease.
In the aircraft industry, there is some disagreement about whether it's
better to have hygroscopic grease (ones that ABSORB water) or hydrophobic
grease (ones that REPEL water). The argument boils down to this: If the
grease is hydrophobic, then any water that gets in will sit in little drops
and possible cause significant corrosion right where the drops sit. If the
grease can absorb the water (is hygroscopic), then any water that gets in is
absorbed and distributed throughout the grease, thus eliminating the drops of
water that can cause excessive corrosion. Of course, the grease is now damp,
and may cause corrosion over a larger area. This is why there is
disagreement about which is better -- drops of water in limited locations, or
having the water diluted in the grease. Obviously hygroscopic grease should
only be used in a well sealed environment where it won't be absorbing water
out of the air.
So, now to brake fluid. Since the brake system is well sealed, hygroscopic
brake fluid (e.g., DOT 3), MAY be advantageous. That is, if a tinny bit of
water gets past the wheel cylinder seals when you are swimming, this water
will be absorbed into the fluid. This MAY be less corrosive to your wheel
cylinders than having the water sit as a drop in the bottom of the wheel
cylinder as would happen with a hydrophobic brake fluid (DOT 5).
I really don't know which is better, but in either case it's a good idea to
bleed all the 4 wheels regularly (like yearly). Personally, I'm not going to
bother to switch to DOT 5.
Roger St. John
White '63
Seattle
PS - There is no need to start with clean fluid in your bleeder jar. There
is no way that you are going to suck fluid all the way up your bleeder hose
from the bleeder jar. That is, all the fluid (if any) that gets sucked back
in through the bleeder screw is going to be the dirty fluid (that just came
out of the wheel cylinder) that is still in your bleeder hose. The clean
fluid in the jar isn't going to get near the wheel cylinder.
[Non-text portions of this message have been removed]