Packard Forum Index » General

Came across an interesting discussion re changing fluids.

Not really getting into the debate of regular vs silicone merits other than the usual reasons promoting the change: higher temp and less of a need to change regularly & no paint damage. Downsides given were expense & never reaching that high temp & one I hadn't heard before -- a softer pedal with silicone. Anyone found this pedal feel to be the case.

Almost unanimous was the recommendation to flush system and change rubber for best results when going from regular to silicone.

What surprised me is some also made the comment that once the silicone change was made it was almost impossible to go back without essentially a complete component change. Reason speculated was once the silicone is in the system, it is very difficult to remove so it reacts badly in the reverse direction. Can anyone confirm this or have run across issues.

I notice that some component mfgs won't warranty new components with silicone. Anyone care to speculate why this might be.

As I have been given to understand it: Dot 3 causes the rubber to swell a tiny bit; no problem. Silicone causes the rubber to swell a tiny bit; no problem. BUT, when you change from one to the other, you get both types (?) of swelling, and then you have a problem.

Have heard of several cases of brake hoses swelling shut after a fluid type change.

Though no major auto manufacturer world-wide uses DOT5 to my knowledge, there are quite a few advantages especially for seldom-used cars, especially museum pieces, which have been well discussed at length.

There really aren't any significant disadvantages that I'm aware of, except that DOT5 will find a leak in a system that DOT3 or DOT4 wouldn't find. I've often heard the comment about a softer pedal but have no experience with that one way or the other. I've used DOT4 for a long time in the 56 Carib with complete satisfaction.

I bow to the above, but been using nothing but silicone DOT-5 brake fluid in my Packards since the late '70s with never a problem. Pedal pressure feels fine, and i've driven other Packards so filled that felt fine, "normal" pedal. Just make sure you flush out your brake system, master/wheel cylinders, lines, with isopropyl alcohol, etc. available at any drugstore, blow the lines/system out with compressed air, before switching to DOT-5.

I'll never go back to DOT-3. It draws water into the system, which rusts your wheel cylinders. A friend has the
same batch of DOT-5 silicone brake fluid in his '42 One-Sixty drophead that he installed in 1978 and it still looks new.

Lotta these silicone campfire stories sound akin to the don't use multiweight/detergent oil, you "hafta" use antifreeze, don't rest a battery on a cement floor, your engine will wear out without ZDDP additive-- that entire decades-old litany of malarkey so-and-so knows someone who heard someone say he heard tell that Henney Penny said...

It's always easier to blame the big bad oil company, the gasoline, the product than deferred maintenance, ancient hoses, et al.