Date: Fri, 25 Jun 2010 14:13:12 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Brake question......
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I was surprised how low the boiling point of brake fluid is.
Dot 3 is only 273F I think,
which isn't that far above the boiling point of water , as a handy reference.
Vanagons use Dot 4 Brake Fluid of course...
forget what the boiling point of that is, but it's somewhat higher ..
and it's not anything like 400 degrees I don't think.
shoot the temps of front rotors sometime after heavy brake use ....they can get way up there.
and yes, it's mandatory to change brake fluid every two years on all cars.
When it's old and thin and black ...
it's probably 70 % water I bet.
'just sitting'......... brake fluid absorbs moisture out of the air. It attracts water practically.
In a high humidity environment, it should be changed once a year.
You may notice some Owner's Manuals say 'add brake fluid from a sealed container.'
and that is a great idea on the blue and gold fluids ..so you can tell when the old is out and new is in.
'usually' products made for racing might be better at racing applications than for daily and regular road use, so check on that I'd say.
I just believe in a high quality Dot 4 brake fluid, and change it twice a year, including clutch hydraulics.
Scott
www.turbovans.com
----- Original Message -----
From: Don Hanson
To: Scott Daniel - Turbovans
Cc: vanagon@gerry.vanagon.com
Sent: Friday, June 25, 2010 1:50 PM
Subject: Re: Brake question......
Right on, Scott.
A loaded Westie, maybe an automatic without much engine braking, going down a long steep grade...that is "Brake Fade...waiting to happen" if you apply the brake the whole time to control your downhill speed. If you apply continuous braking all the way down a long hill, the pads and rotors get real hot and transmit that heat into the caliper and through that to the fluid. Real hot brake pads are also less effective, requiring more braking as the heat builds, so you have to push harder, creating even more heat...a vicious cycle..
The most effective way to descend in a heavy vehicle with small brakes is to apply them firmly and slow the vehicle below it's 'perfect speed', then get off the brakes and let it build back up to speed (allowing the brakes to cool off some) Watch the truckers go downhill.
Brake fade is mostly caused by the moisture in your brake fluid turning to steam. Brake fluid has a very very high boiling point but it also loves moisture...So over time your brake fluid will absorb a small amount of moisture...a drop or two in the whole vehicle's brake system is all it takes to create a lot of steam....Water expands and creates a lot of steam which is 'compressable' unlike brake fluid...So at 212f...which is nothing when you are talking brake temps...your brake system can boil the moisture in old stale brake fluid and give you the classic "Soft Pedal" of brake fade....You push and push harder but all you are doing is compressing the steam that's been created by Hot Brakes...
Changing brake fluid regularly is good. Once you experience Brake Fade...you will become a believer...if you live.
In my road racing car I changed brake fluid every race weekend, at least. Sometimes I would change between sessions , if I'd really cooked the brakes. I use ATE Super Blue and ATE Gold, alternating the two so I can see when I get Fresh new fluid out of my bleeder valves..Cheap insurance and not difficult with a Power Bleeder set up.
Don Hanson
On Fri, Jun 25, 2010 at 12:48 PM, Scott Daniel - Turbovans <scottdaniel@turbovans.com> wrote:
hi.
no , that is not classic brake fad.
Brake fad is when you have decent pedal, but brake pads and calipers have
gotten so hot from continued or hard downhill use, that the brake fluid
starts to boil...
then you have essentially no brakes, are barely any.
btw ...
continued light use ..or steady light use, as in a long decent is not the
right thing to do at all.
that just builds up heat.
Instead...use the brakes hard enough to drop some speed, then don't use
them ...
given them some cooling time...then use again a little harder, then let cool
etc...
And brake in new pads properly too. Another subject.
Scott
www.turbovans.com
----- Original Message -----
From: "Paul" <wognacious@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, June 24, 2010 11:54 PM
Subject: Brake question......
Is this what I've heard described as "brake fade?" I'll be going down a
hill
and the pedal feels normal, if there is such a thing, and once in a while
it
feels like the pedal all of a sudden will go right down to the floor
board.
I
