[Healeys] Brake Fluid -- Silicone vs. glycol

Bob Spidell bspidell at comcast.net
Sun Jul 25 17:13:22 MDT 2021

I'd add that DoT5/Silicone BF should be flushed occasionally (like, 
every 5-10 years). It doesn't absorb moisture, but supposedly water can 
pool in low spots (you'll get some condesation in the reservoir every 
time you check the level). I usually have to do something to my brake 
systems that often anyway. I've noticed that DoT5, which is purple 
coming out of the bottle, turns clear/amber near the wheels where, of 
course, heat is generated.


ps. I've followed several threads where owners are reporting 
crystallization or gelling of Dot3/4, and no one has come up with a 
definitive cause.

On 7/25/2021 3:36 PM, Gary Anderson via Healeys wrote:
> Having co-authored the book on restoration of Austin-Healeys and been 
> involved in classic cars for over 30 years, I've confronted this 
> question in many forms and many times. I've talked to vintage racers 
> and great collections managers on whose decisions thousands of dollars 
> and human lives can depend.
> Out of all this, the simple neutral answer depends on how you will use 
> the car.
> Assuming you've replaced the complete brake system AND all seals and 
> gaskets, then:
> If you use your classic car regularly and maintain it carefully, then 
> by all means use glycol-based fluid and change it at least every two 
> years (more frequently if you're racing and/or doing long tours).
> If you don't use your classic car regularly -- it's parked for months 
> on end or used for display and show rather than regular driving and 
> touring -- then use silicone fluid.
> Regarding the proviso above, if you're not changing gaskets and seals, 
> then use whatever fluid was used before, but with glycol replace it 
> every two years at minimum and with silicone, check the level 
> frequently and top up as necessary.
> Let me know if you can find a classic collection manager or racing 
> driver who will disagree with that answer.
> Best
> Gary Anderson

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