Power Top Fluid
 

A question for you guys with convertible power tops :

According to my GM shop manual, the recommended fluid for my power top pump
is brake fluid. Now knowing what happens when brake fluid meets paint and
the number of possible areas for leakage, I'm considering changing it for an
alternative fluid.

My first thought was to use the standard brake fluid replacement, DOT 5
silicon fuid, which is well proven for brake system applications. But after
discussing this with my local restoration shop, he advised me against it
..... stay with brake fluid in this application ... he's found it gets
whipped up by the pump and foams. I suspect most manufacturers use a
similar pump design, a single 3 lobed impeller, driven by a 12 volt DC motor
with an attached reservoir, so some of you may have experimented with
something else.

Also, looking at the available hydraulic fluids on the market, and not
knowing much about them, there is a bewildering number of choices.

Any experiences out there?? I've posted this in alt.autos.antique &
rec.autos.antique

I went through this same situation and found that the fluid of choice is
none other than good old transmission fluid. Bleed out the old brake fluid,
do not forget to bleed out the lines as well. Then replace with transmission
fluid and life will be good. I have used this and found it works very well.
Good luck Greg


"Mike Atkins" > wrote in message
...
> A question for you guys with convertible power tops :
>
> According to my GM shop manual, the recommended fluid for my power top
pump
> is brake fluid. Now knowing what happens when brake fluid meets paint and
> the number of possible areas for leakage, I'm considering changing it for
an
> alternative fluid.
>
> My first thought was to use the standard brake fluid replacement, DOT 5
> silicon fuid, which is well proven for brake system applications. But
after
> discussing this with my local restoration shop, he advised me against it
> .... stay with brake fluid in this application ... he's found it gets
> whipped up by the pump and foams. I suspect most manufacturers use a
> similar pump design, a single 3 lobed impeller, driven by a 12 volt DC
motor
> with an attached reservoir, so some of you may have experimented with
> something else.
>
> Also, looking at the available hydraulic fluids on the market, and not
> knowing much about them, there is a bewildering number of choices.
>
> Any experiences out there?? I've posted this in alt.autos.antique &
> rec.autos.antique
>
>

> According to my GM shop manual, the recommended fluid for my power top
pump
> is brake fluid. Now knowing what happens when brake fluid meets paint and
> the number of possible areas for leakage, I'm considering changing it for
an
> alternative fluid.
>
My friend has a 1953 Skylark and he uses transmission fluid. Especially
after a cylinder leaked back when he used brake fluid, and he had to repaint
the rocker.

Rabbit

OK, thanks Greg & Rabbit .... good 'ol Dextron III it is !! This will
certainly ease my mind.
"Rabbit" > wrote in message
...
>
> > According to my GM shop manual, the recommended fluid for my power top
> pump
> > is brake fluid. Now knowing what happens when brake fluid meets paint
and
> > the number of possible areas for leakage, I'm considering changing it
for
> an
> > alternative fluid.
> >
> My friend has a 1953 Skylark and he uses transmission fluid. Especially
> after a cylinder leaked back when he used brake fluid, and he had to
repaint
> the rocker.
>
> Rabbit
>
>

Synthetic Dexron II is better yet!

It's easier on the seals, and is easier on the impeller and motor shaft
bushing, which is wet. The seal is behind it on the GM at least.

Refinish King

PS
If you were using urethane paint, you wouldn't have to worry about
repainting for a brake fluid leak, and Valvoline makes a great Synthetic
brake fluid that does not harm paint!


"Mike Atkins" > wrote in message
...
> OK, thanks Greg & Rabbit .... good 'ol Dextron III it is !! This will
> certainly ease my mind.
> "Rabbit" > wrote in message
> ...
> >
> > > According to my GM shop manual, the recommended fluid for my power top
> > pump
> > > is brake fluid. Now knowing what happens when brake fluid meets paint
> and
> > > the number of possible areas for leakage, I'm considering changing it
> for
> > an
> > > alternative fluid.
> > >
> > My friend has a 1953 Skylark and he uses transmission fluid. Especially
> > after a cylinder leaked back when he used brake fluid, and he had to
> repaint
> > the rocker.
> >
> > Rabbit
> >
> >
>
>

> According to my GM shop manual, the recommended fluid for my power top pump
> is brake fluid. Now knowing what happens when brake fluid meets paint and
> the number of possible areas for leakage, I'm considering changing it for an
> alternative fluid.

I'd say, "use brake fluid and be careful with maintenance." Details
follow.


> My first thought was to use the standard brake fluid replacement, DOT 5
> silicon fuid, which is well proven for brake system applications.

I respectfully differ -- "standard" brake fluid, to me, is DOT 3,
though I use DOT 4, which is only a bit more expensive, compatible
with it, and higher in boiling point. DOT 5 silicone based brake
fluid is incompatible with DOT 3/4, should never be mixed with them,
and, in my opinion, shouldn't be bothered with unless (a) you are
completely rebuilding a brake system for a performance application or
(b) you have a car whose manufacturer specifies and uses the stuff.

Now, the power-top pump is obviously a less critical system, even if
Murphy's Law causes it to fail with the top at a 45 degree angle. But
still, putting silicone fluid in there should be done only as part of
a very thorough flush. See for instance "Contamination and sludging"
on
http://www.sdvsa.org/BrakeFluidFacts.htm


> Also, looking at the available hydraulic fluids on the market, and not
> knowing much about them, there is a bewildering number of choices.

Most hydraulic fluids more closely resemble power-steering or
automatic-transmission fluid than they do brake fluid: basically they
are oils, whereas DOT 3 and 4 brake fluids are various esters and
ethers and glycols (see the Material Safety Data Sheets available on
the Web from the manufacturers for details).

CAUTION, and if we're talking about the brakes, WARNING! You can do
major damage to some of the rubber formulations found in brake
systems, and perhaps other hydraulic systems meant to run on brake
fluid, if you introduce petroleum oils or greases!

Best of luck,
--Joe