RE: [Chrysler300] Pros and cons of silicon brake fluid

[<john_nowosacki@xxxxxxxxxxx>]

Yikes,

Now I must ask my question regarding my disc brake conversion on my G.

 

Does this mean I need to change to Dot 4 instead of the Dot 3 that was in my master cylinder with front disc brakes?

 

________________________________

From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of Warren Anderson
Sent: Thursday, May 22, 2008 7:22 PM
To: chrysler300@xxxxxxxxxxxxxxx; Narve Nordanger
Subject: Re: [Chrysler300] Pros and cons of silicon brake fluid

 


Really nice post. 

Adding only, the boiling point of DOT 4 is higher than DOT 3 which is what drum brake cars use. DOT 4 I consider to be necessary for European, high performance disc brake applications. I really doubt any normal use old Chrysler with drum brakes will ever boil DOT 3. Moisture migration is greater with DOT 4 than with DOT 3. 

The DOT 3 & 4 synthetic fluids I have seen but have no in use information on. As with so many things, the possible non compatibility of old rubber compounds and this stuff would concern me. The published boiling point is once again so high I really wonder why old drum brake cars would need it. 

If you accidently put DOT 4 fluid intended for your BMW in your 300 with DOT 3 in it, that is not a problem. DOT 3 or 4 in a DOT 5 system and there is no idea what that mess might be. 

Maybe there is a member that has seen something about DOT 5.1 in old car applications. That stuff is very high boiling point with lower viscosity, which I find interesting, and has some moisture migration advantages also. It is not silicone; not related to DOT 5 at all. 

Warren Anderson
Sedona,AZ

Having almost 20 years experience with using silicon fluid on my C-300 and a
few Type 1 VW products, some lessons learned can be identified.

Compared to DOT 3 and 4 the silicon brakes do not seize up, especially disc
brakes which otherwise frequently get stuck (VW discs which needed freeing
up every 3 months of standstill with mineral, performed faultlessly for the
next 10 years with silicon), there is less risk of rust in the cylinders as
it is not hydroscopic and you will have less fading by hot brake fluid
(higher boiling point). It does neither attack your paint.

The downsides are sticking brake light switches (every 12 months on the VWs,
also frequently on the C-300) rendering the switch either permanently on or
off, it is actually compressible as John L has recognized (I once bottomed
the pedal on one VW during panic braking, and there was no air in the
system), and if you spill any it is really hard to later repaint the spot
without silicon fish eyes. When introduced, the silicon fluid also gained a
reputation for destroying old rubber gaskets/cups, so everything renewed is
recommended. Blending silicon (DOT 5) with mineral fluid creates "porridge",
so a total clean-out (spirit) is essential before changing back and forth.
As I have recently learned, the engine runs very poorly (not at all) if you
get DOT 5 into the intake.

Bottom line: Unless you are racing, silicon brake fluid is beneficial for
cars with external brake light switch as Tony Rinaldi recommends. For cars
with pressurized brake switches, stick to mineral and change it every 2-3
years to avoid sticking and rust.

Narve Nordanger

(out to fix my C-300 brakes this week-end)

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