Brake Fluid DOT 3 vs DOT 5

[Scott Howard]

I am in the process of a complete brake system rebuild on my 1962 Series 62 CV. Has anyone used DOT 5 brake fluid?  Good? Bad? or Indifferent?   Thanks Scott.   CLC #22304

[Larry]

I can give you what little I know.

I have 2 collectible vette that I run dot 5 in. I was told its better for the vette calipers to avoid leaks

On any of my other cars I run plain on regular brake fluid.

The problems with silicone is

It loves and absorbs moisture.
it gets microscopic air bubbles in it with a normal pump and bleed brake bleed (must use a power bleeder to avoid the bubbles)

its expensive

[Geoff Newcombe #4719]

DOT 3 readily absorbs moisture, not DOT 5.  I use DOT 5 whenever I do a fluid change, I have used it in all of my 60s Cadillacs and other older cars that I have owned over the years and have it in the 60 Cad. I own now.  DOT 5 is used by the Harley-Davidson factory in all their new motorcycles and has been for many years.  It is a real boon to old car nuts especially in cars that are not driven much.  A few older brake systems (especially British cars I am told) have different rubber compounds in their seals that are not compatible with DOT 5.  I have always been able to bleed my brake systems with the good old pump and bleed method and have never had to use a power bleeder.  DOT 5 suppliers can be found in Hemmings that sell in bulk (gallon containers) that help keep the price down, worth the extra price in my opinion.

[Scott Howard]

Thanks Geoff, That is pretty much what I thought and have been finding out from other people.  Scott CLC # 22304

[Art #22010]

When rebuilt my 49 I went to DOT 5 as my master is located along frame rail.  Far superior.   System must be completly drained of old, preferably new wheel cylinders also.
  like they say, set it and forget it.  Art