RE: A&G's Re: [Chrysler300] Convertible top oil
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RE: A&G's Re: [Chrysler300] Convertible top oil

I'm with you John, if they can make seals that stand up to hydraulic oil in car jacks, lifts, forklift trucks for years, why not brake systems?   Sure, older rubber parts may not have been compatible, but what about modern seal material?  I've had a hydraulic car lift in my shop since 1989, never had a leak or had to add fluid.  Not to start a huge discussion here, but, I too use silicone brake fluid and swear by it, have had it in my 300G since 1978. 


The only thing I can think of, beyond potential rubber incompatibilities, is that brake engineers like the idea of a fluid (DOT 3,4) that is hygroscopic, that is, it absorbs moisture throughout the fluid, and keeps it from settling in low spots, and gradually lowers the boiling point of all the fluid.  This eliminates points were water can puddle that could boil, turn into a gas, and result in brake failure.  Also, corrosion would be reduced because the fluid absorbs the water.  But the down side is it is always there sucking moisture into the fluid unlike hydraulic oil or silicone fluid, and needs to be bled every 2-3 years.  I've gone as long as 18 years with the silicone filled brake system in my G without flushing the brake system, until I noticed the car pulling a bit to one side.  Once I noticed that, I pulled the front hubs and saw that the lower cylinder on one side began to leak.  Removed the brake cylinder, inspected it and found corrosion at the lowest point, indicating the presence of water causing the corrosion.  I rebuilt the system, had the wheel cylinders resleeved with brass, refilled with silicone fluid.  Now I bleed about every 7-10 years just to be safe, but it sure is better than every 2-3 years.  I have heard from other club members that have converted to silicone fluid in the late '70s and not bled since, but I don't know how often those cars are driven.


Bob J


From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of John Grady jkg@xxxxxxxxxxxxxxxxx [Chrysler300]
Sent: Saturday, July 09, 2016 8:52 PM
To: Allan <agmoon@xxxxxxxxx>
Cc: chrysler300@xxxxxxxxxxxxxxx; dan300f@xxxxxxx; Fern Rivard <crc@xxxxxxxxxxxx>
Subject: Re: A&G's Re: [Chrysler300] Convertible top oil



I do not understand , never did , advantage of brake fluid in brakes ? Why not hydraulic oil , like construction equipment ? Temp resistance maybe , but water in brake fluid boils . Maybe it was the rubber at the time ( 1920's )  deteriorated in oil . Not now with right stuff .( except German rubber) ( MB junk)  Might relate to the change in top cyl fluids in 62 . Better seals , oil resistant, allow  oil.  Atf and ps fluid are both essentially 10 W oil with additives . Semi auto trans was 10 W .

I use silicone exclusively in brakes because military says to . Good enough for me . But silicone oil is like 10 W oil physically . But it loves rubber and other way round . Biggest issue is $ but you can find mil surplus by the half gallon . 

Maybe one of our mopar engineers knows "why brake fluid ? " . 

If you do not change religiously in MB brakes fail as in 2000$ worth of fail . Yet I had 37 Packard with original brakes when I bought it that still worked ok . Strange stuff ... 

Sent from my iPhone

On Jul 9, 2016, at 4:53 PM, 'Allan' agmoon@xxxxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:

We've heard this before about brake fluid.


Anybody know why brake fluid would be manufacturer used over hydraulic oil.  Brake fluid seems just plain dumb for all kinds of reasons, not the least of which is that it is hygroscopic for heaven's sake - duh...  But we are not engineers.  What do you engineers say?


Since it is available, today we guess that one should use top of the line true synthetic hydraulic oil but which brand and exactly which Spec.?  On expensive to fix cars, people today are using more and more Red Line, Royal Purple, Amsoil and the like.


We are interested in reading what knowledgeable others have to say.


Sooo what should we do and why?







----- Original Message -----

Sent: Saturday, July 09, 2016 3:57 PM

Subject: Re: [Chrysler300] Convertible top oil



Well Dan, I recently  had to replace the convertible top pump and motor assembly in my 300H covertible from Hydro Electric in Florida. The original had packed it in last summer while attending a car show where it couldn’t  move the top up or down properly unless we gave it some manual assistance. I was expecting to get some kind of warranty from them but they said that it was too old and wouldn’t cover it! I told them that I had purchased the assembly years before restoring the car but they didn’t buy that.

Now getting to what oil to use, I prefer using power steering fluid as it is colorless and less likely to stain anything if you should develop a leak in the system. The replacement pump and motor received from them was already filed with automatic tranny fluid (the red stuff). Some of the early cars used power brake fluid which would be a disaster if a leak should occur.

Why would you want to replace the oil in the system in your 66 300? I could see doing so if it looks like it’s dirty or?

Cheers from Fern with silver/lilac 300H convertible located in SE BC




Sent: Saturday, July 09, 2016 12:42 PM

Subject: [Chrysler300] Convertible top oil



Hi all:


Can anyone apprise me of the best oil to use in the hydraulic lift of the convertible top of my 1966 300?  Should I purge the old oil?  If so, what liquid should I use for purging?




Dan Reitz

Bell Canyon, cA


Posted by: "Bob Jasinski" <rpjasin@xxxxxxxxxxx>

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