[T3] Battery Install, Oil Change & Brake Fluid Reservoir

[Jim Adney]

When my '68 Square was just a few years old, I started to have problems 
with the calipers sticking, so I decided to learn how to rebuild calipers. That's 
when I discovered that the OE brake fluid was blue, later determined to be 
ATe Blue, a DoT-4 brake fluid. ATe Blue is still available, but it was too 
expensive and too hard for me to get at that time in my life, so I switched to 
domestic DoT 3 or 4. As brake fluids, those worked just fine.

Eventually, however, as I acquired a wife and a second Square, I started 
having more trouble than I liked, trying to keep the calipers and master 
cylinders on two cars all in good running condition. Seemed like something 
always needed rebuilding every couple of years.

In the meantime, a good friend of mine bought a '71 Super Beetle and had 
his dealer install STP Silicone Brake Fluid in it. This was before there was a 
DoT-5 standard, so this did not have any DoT listing. I'd never heard of the 
stuff, but the memory stuck in my mind. Eventually, this led to a phone call to 
Dow-Corning, where I found a fellow by the name of Chip Nelson who had 
run the D-C test program for silicone brake fluid, which D-C had developed 
for the military. We had a couple of hour-long phone calls where Chip 
shared huge amounts of useful information. That was in 1977. I still have my 
notes from those conversations.

For their testing, D-C offered to put their brake fluid in any employee car, as 
long as the employee agreed to let them do all the brake service on that car 
for free and to inspect and replace parts as necessary. They did this for 
several years, on as broad a spectrum of auto makes as possible. Chip 
explained that, for some reason, the only systematic problem they 
encountered was with Corvettes, where they found that the factory flare 
connections tended to be not quite as perfectly sealed as one would hope. 
They did not leak normal fluid, nor did they leak the silicon fluid, but they 
sometimes sucked in air on the pedal upstrokes.  

Every year, Chip and his team would replace brake parts on a number of 
those cars, to be cut apart to look for wear and rust. There must have also 
been a control group, because they published photos of cut apart cylinders 
that had been used with both silicone and normal brake fluid. The silicone 
bores were always shiny while the normal ones showed rust.

Chip sent me a sample bottle of their brake fluid, which by that time had 
been qualified as DoT-5. I cleaned out the brake system in my beige '71 
Square and managed to fill the system from that small sample bottle. From 
that time on, that system never needed any new hydraulic work.

Why is DoT-5 better? It's better for two reasons. First, it does not absorb 
water, so rusting of internal hydraulic surfaces in hugely reduced. Second, 
it's a MUCH better rubber to metal lubricant, so the rubber seals that have to 
slide along a metal bore tend to almost never wear out. I had found seal 
wear in master cylinder bores to be a big problem with DoT-4 and rust in 
caliper bores to be even more annoying. DoT-5 fixed both of those problems.

Around 1980 I found a supplier for DoT-5 and started to install DoT-5 in 
various customer cars, all old cars, all daily drivers. I stopped keeping 
records of this after that list got past 50 cars. In that time, I believe I only had 
two "failures." One was with a Volvo master which stopped working. I rebuilt 
that master and found that one of the pistons was badly corroded and a 
chunk of that crusty white oxide had fallen off and worn a groove in one of 
the rubber seals. So I can't blame the DoT-5 for that.

The second "failure" was some sort of British sports car where the owner 
wanted to do the work himself. He was never able to get the system bled and 
finally took the car to a different shop, where they replaced EVERYTHING 
and bled the brakes with their usual DoT-3 or 4. I never got to see any of 
that, so I have no way of knowing what the actual problem was, but I'm 
guessing it was user error.

Over the years, I've heard many people tell me things about DoT-5 that 
simply aren't true. I've heard that if you allow it to mix with DoT-3 or 4 it will 
turn to jell, but I have a little bottle of DoT 4 plus 5 that's been mixed since 
1977. They're still there. You can shake it up and mix them as much as you 
like, but they will slowly separate and they're still perfectly fluid.

I've been told that DoT-5 isn't compatable with some of the rubber 
compounds used in brake systems, but I've never seen a problem, and Chip 
explained the 4 (yes, only 4) different elastomer families EVER used in 
hydraulic brakes, and DoT-5 is compatable with all of them, even natural 
rubber, which was last used, even in rebuild kits, sometime around 1966.

(Some of you may know that old British cars were known to use natural 
rubber brake seals, which required special brake fluid. Now they can use 
DoT-5. OTOH, this is no longer a problem, because those old cars have 
surely had all their seals replaced with seals made later than 1966.)

I've also been told that DoT-5 is more compressible. That's true, but the 
difference is insignificant and imperceptable. This complaint often comes 
from the 914/4 crowd, where there's a huge problem getting all the air out of 
the proportioning valve. Yes, I've been there and done that, but once you get 
the last of the air out, the brakes are fine.

Okay, how about downsides? There are three. First, it's expensive. Second, 
it's lighter than the glycol based DoT-3 & 4 (and 5.1.) Since the silicone is 
lighter, there are places where normal bleeding won't expell the old fluid; 
you'll just keep bleeding silicon fluid off the top. You can overcome this 
problem by mixing the fluids using turbulance, which is easy to create in 
master cylinders and wheel cylinders, but not possible in all parts of our front 
brake calipers. To bleed our front calipers, just unbolt them and bleed them 
slowly while they are upside down, with the bleed valves on the bottom.

The late Type 3 calipers, with two bleed valves, make this easy: Just bleed 
the air off the top and the old brake fluid off the bottom. I like to go back and 
bleed a tiny bit off the bottom after a few weeks of daily driving, just to get 
any remaining old fluid out, and to give me an idea of how good a job I did of 
getting all the old fluid out in the first place.

The third downside is that DoT-3 is probably not suitable for use with ABS 
systems in modern cars. This is apparently because there's lots of metal to 
metal contact in the ABS pumps, and silicone is not a good metal to metal 
lubricant. You may wonder about metal to metal contact in a standard brake 
system, but the side pressure on those pistons is minimal and no cause for a 
problem there.

So, not a problem in our Type 3s.

Since 1977, ALL my air cooled VW have had DoT-5 installed in them. I've 
had to do almost no maintenance on the hydraulics of those cars. The 
largest benefit may be with old cars in storage. When I got my '69 out of 
being stored for over 10 years, the brakes were still perfect. OTOH, I've got 
a '73 in storage for about 30 years. It's pedal now goes to the floor, so I 
know that master is going to need work.

For anyone who's interested, I have a FAQ I wrote on how to install DoT-5. 
I'll gladly email a copy to anyone who requests it.

-- 
*******************************
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
*******************************