Re: [Chrysler300] Brake Fluid for a 300F

I have both a 1957 300C and a 1962 Chrysler 300H that both have been running with silicone fluid for over twenty years now with now issues, except that since I had repeated failures of the brake light switch on the C, I eliminated it and to a mechanical switch mounted next to the brake pedal to activate the brakes lights such as was used in 1962 Chrysler models.. Since then, no issues at all.

Hoever, after a brake job on my 1960 300F about 10 years ago also using silicone and redoing the brake switch to match the H, I recently went out to my garage to take the F out for a spin and found to my dismay that there was no braking available at all. I have not had the opportunity to investigate the matter yet, but I have been concerned about this since it happened recently. All I know is that the master cylinder was completely empty and was unable to trace any fluid on the garage floor.

Recently I went to Karp's Brake service near where I live here in California and asked the proprieter Jeff what he recommends using in older cars, silicone or regular brake fluid (Dot 3 for example)? Keep in mind that Jeff is one of the few persons that gets 1955 Chrysler brake systems to work again when most cant and he repairs all kinds of brake systems from the past and has been doing this for decades now on all makes and models. He said his conclusion over the years is that there are some seals in replacement parts that will not maintain their integrity using silicone fluid, and it is hard to know going in which replacement parts will ulimately fail using this fluid. just as some fluid brake switches as in pre 1962 models use and also fail. After many years of people asking him this question, he maintains that he recommends using converntional brake fluid in the systems of our old cars for this reason - just be sure to flush the brake system every few years to keep moisture out of the system. Here in California, the climate is generally very dry, so flushing may not be needed quite as often as in more humid areas of the country/world. My cars are kept in a sealed, climate controlled garage so the change intervals can be extended some. But Jeff at least was pretty firm on his conclusion about this use of conventional fluid being the best option. Before my experience with my F, I would have probably still be using silicone fluid - but that was an eye opener for me and a bit scary and very unexpected. I personally will rely on experts such as Jeff for what I will do. I was lucky for some time with my C and H, but on my F I was not. .

Steve Albu

On Tue, Mar 24, 2020 at 3:06 PM dverity@xxxxxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:

Most 61’s still had a pressure switch. I had silicone fluid in my old G, and always had a good pedal. I had the car for 75,000 miles, so I did change a few brake light pressure switches. Good switches last, cheap ones don’t. My 66 Imperial has had silicone in it since 1987. Still the same wheel cylinders and master. II t also has a good pedal.

Don

From: mailto:Chrysler300-noreply@xxxxxxxxxxxxxxx

Sent: Tuesday, March 24, 2020 3:59 PM

To: John Grady

Cc: Ron Waters ; chrysler300

Subject: Re: [Chrysler300] Brake Fluid for a 300F

I have a G that I put silicone fluid in it about 40 years ago and never had a leak in a wheel cylinder or the pressure brake switch until after it was in a body shop getting rust repaired for 4 years. At that point a wheel cylinder failed. I don't recommend going 35 years without changing the fluid, as had I changed it every 10 years or so, that cylinder would likely not have failed. I am replacing the master and wheel cylinders and will use silicone fluid again. I use Dot 3 or 4 in my drivers and change the fluid when I replace brake pads. If I put Dot 3 in my G I would change it every year or 2 max. I will probably never wear out the shoes on my G as I doubt I will drive it that much. I will change the silicone after 10 years if the virus doesn't get me first.. I mentioned that silicone had not affected my pressure brake light switch before on here and someone wrote me back saying that G's didn't have a pressure switch. My car was delivered in November 1960 and is equipped with a pressure switch.

Loren Nelson 300G in spring blooming N Georgia

On Tue, Mar 24, 2020 at 11:38 AM John Grady jkg@xxxxxxxxxxxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:

Moisture cannot mysteriously get to brake line in first place with silicone , but glycol carries it just as you say and once saturated it settles out in wheel cylinder bottoms .

So if you change it often you are ok . But it also absorbs it from air as air pressure changes at master over a long time , then you push it into system . Silicone does not . Army does not have soft pedals. It is difficult to install right — really .

Cars were made for ten years life, we are 60 now . Water is in the glycol . And I admit to not tracking this on so many cars . Silicone does not have the problem at all . I like that . To each his own.

Often soft pedal has in fact nothing to do with fluids . Often mismatched diameter shoes and new drums or shoes . Why people give up on brake designs that won at nascar 55 and 56 .. add in skill of guy doing it . My first attempt on an F was a disaster , all new stuff back in 67

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On 24 Mar 2020, at 11:12 am, 'Ron Waters' ronbo97@xxxxxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:

John -

The way I understand it, moisture gets trapped in the brake lines. Having a brake fluid that absorbs moisture is a good thing, since otherwise it has no place to go and settles either between the fluid and the inner line, or by the line-to-wheel cylinder connection, which will cause rust to form. Since DOT 5 does not absorb moisture, that may lead to the condition just described. DOT 3/4 starts out as a golden color, but turns darker as it reaches a moisture saturation level. So I would change out DOT 3/4 every five years or so and your brakes will be happy. Having a soft pedal, IMHO, is a worse alternative to this. Very scary.

There is also something called DOT 5.1, which I haven't researched. Anyone want to chime in ?

Ron

From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of John Grady jkg@xxxxxxxxxxxxxxxxx [Chrysler300]
Sent: Tuesday, March 24, 2020 10:02 AM
To: nick@xxxxxxxx
Cc: Mister Michael; Chrysler 300 List
Subject: Re: [Chrysler300] Brake Fluid for a 300F

FYI — Soft pedal with silicone is because you got air entrained in it . Takes months to get out , If ever , if in a car . Must pour very carefully from undisturbed container sitting on a shelf , still for a year , imho. And extremely smoothly , slowly ideally down a paper ramp into master . Anything to avoid aerating it . Just dumping it in makes tiny bubbles . Micro bubbles stay suspended. Soft pedal. I would avoid pressure bleeders . Obviously if you shake can once you are done for .
It is standard in military ( where I got mine surplus —some large cans on eBay )   . Rubber loves silicone , —silicone seals rubber and preserves it twenty years or more . Critically, it does not absorb water .I really believe “sealed   for life” .. like a stored military truck. But if you do not know about the easy aeration it will not work .

All glycol absorbs water ; on our cars it ends up over many years in the bottom of wheel cylinders and makes a rust pit as it is heavier than glycol.. One day you get a very big sudden surprise .

On several of my cars I added a micro switch to pedal mount to get rid of problematic and in the way hydraulic switches. See 70’s dodge trucks for idea /switch , or make bracket yourself for a real 15 amp large body micro switch . Pedal up holds it open. Helps with dual master room and plumbing too . Although not absolutely sure on any given pressure switch, silicone is more chemically innocuous than glycol (?) so switch failure is most likely due to lousy switch — not silicone   ,— plus, and a biggy , a spilled or sprayed drop of glycol , and your paint is absolutely trashed due to the chemical aggressiveness. A leaking master gasket took all the paint off my firewall , under master .

MBenz requires new brake glycol fluid every two years . I did not do that, result was $ 2000 in bills as rubber in ABS system valves fell apart and seals in rear axle disc brakes too, brakes failed after 5-6 years. ... ...personally I think due to crappy German rubber , but it happened .

Temp differences in glycol DOT rankings mean little on drum brakes , but critical on discs . Might as well use best , however.

I would not use the stuff on a rebuild.     I have seen those pits on 4- 5 300F, enough for me -/ — and once had the sudden brake failure they imply . As shoes wear , or are replaced , seal moves to new place in wheel cylinder can uncover pit, your brake fluid squirts right out around seal lip .

Just info , your mileage may vary . Most of above info learned the hard way ..... If you go glycol , change it every few years .. keep record..

John

Ps , glycol probably ok in a car driven a lot , gets warm under hood frequently water vapor probably leaves due to higher vapor pressure etc . But a sitting car must soak it up .. military does not have “ soft pedal ”

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On 23 Mar 2020, at 11:19 pm, nick@xxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:

Do not use synthetic if you’re still using the original brake light switch. Supposedly it will cause it to leak and fail. I just use regular brake fluid.

From: Chrysler300@xxxxxxxxxxxxxxx <Chrysler300@xxxxxxxxxxxxxxx> On Behalf Of Mister Michael milwaukee241@xxxxxxxxx [Chrysler300]
Sent: Monday, March 23, 2020 8:17 PM
To: Chrysler 300 List <chrysler300@xxxxxxxxxxxxxxx>
Subject: [Chrysler300] Brake Fluid for a 300F

Ready to fill up the master cylinder after replacing all lines. Which brake fluid is most recommended for our cars? Used silcone in other classic cars and have had soft pedal. Tempted to use the original dot 3? Never had a problem with the stuff.

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