Silicone or Dot 3 Brake fluid

[Jeff P.]

I'm sure that this has been brought up before. I had calipers SS Sleeved. Here in the east would Silicone be an ok choice. Thank You Jeff

[Edward J.]

Re: Silicone or Dot 3 Brake fluid

Jeff, you can use the dot 4 fluid its a step above the dot 3 , I don' think dot 5 fluid is what you want to use.

There are dot 3 or 4 syth. fluids thats out there, castrol,valvoline etc.

[Michael G.]

Re: Silicone or Dot 3 Brake fluid

Silicone brake fluid systems seem to be a touchy subjuct among us members. Am soon to finalize my new brake system and am looking to use silicone brake fluid as well. Have read many good things about the use of silicone brake fluid as well as opposing views.

Ed.....you seem to have an opinon about the use of Dot 3 and 4 over silicone fluids. Why do feel it's better as opposed to a silicone system?

[Edward J.]

Re: Silicone or Dot 3 Brake fluid

Silicone brake fluid systems seem to be a touchy subjuct among us members. Am soon to finalize my new brake system and am looking to use silicone brake fluid as well. Have read many good things about the use of silicone brake fluid as well as opposing views.

Ed.....you seem to have an opinon about the use of Dot 3 and 4 over silicone fluids. Why do feel it's better as opposed to a silicone system?

Mike, I Don't think silicone will react well with the rubber brake seals, as the difference between the dot 3 and dot 4 is just a higher boiling point. and with the syth. dot 3 or 4 theres alittle longer life between flushing, and Dot 3 is what the factory fill is.

I Think leave the dot 5 to the euro.cars ( BMW Mercedes)

[Terry M.]

Re: Silicone or Dot 3 Brake fluid

I'm sure that this has been brought up before. I had calipers SS Sleeved. Here in the east would Silicone be an ok choice. Thank You Jeff

Jeff you are right, it has been brought up before -- search is your friend.

In the early 1980s, when I had my calipers on the 1970 SS sleeved, I chose the opportunity to rebuild the master cylinder (although with just over 50K on the car it was hardly necessary) and I installed DOT5 fluid. Some twenty or so years later I flushed through fresh DOT 5 just for peace of mind. I haven't had a lick of brake problems in over thirty years and around 11K miles. I am a believer in DOT5. I have no fear of damage to my paint because of the brake fluid.

I must add it is essential to clean the brake system of the old glycol fluid before adding the DOT5, Alcohol and clean dry shop air will work fine. Filling the empty system will be a chore unless one uses a power bleeder of some sort. I used gravity, and it took several days. If I had it to do over again I would get a pressure bleeder like John Hinckley recommends.

[Jim T.]

Re: Silicone or Dot 3 Brake fluid

I have used silicone DOT5 in my 68 convertible for about 25 years now. Have not changed it since it does not absorb moisture like DOT3 and DOT4. In my master cylinder the fluid is still clear enough that I can see the bottom of the two separate fluid cavities when I remove the lid to check the fluid.
I have used it in my 1970 coupe for about 22 years. The 68 has manual brakes and the 70 has power brakes. My 70's stopping ability is impressive to me.
I switched my MG's hydraulic clutch fluid to silicone about 15 years ago. Have had nothing but good operation and no rebuilds. The seals like it.

[Larry M.]

Re: Silicone or Dot 3 Brake fluid

Everyone has their own preference regarding brake fluid.....sort of like engine oil and car wax. I can respect that.

Like Terry M, I completely redid the brake system on my 1967 and installed DOT 5 brake fluid. That was in 1995. No maintenance or failures since that time (15 years), although I recently re-bled the brakes after rebuilding the rear trailing arms. The first few ounces of old brake fluid were yellow/amber colored instead of the normal purple hue. But the fluid was clear and no corrosion is/was apparent.

Another example to consider.

Larry

[Terry M.]

Re: Silicone or Dot 3 Brake fluid

Everyone has their own preference regarding brake fluid.....sort of like engine oil and car wax. I can respect that.

The first few ounces of old brake fluid were yellow/amber colored instead of the normal purple hue. Larry

I believe that with time DOT5 loses the purple color and the fluid becomes amber. I have noticed that on my 1970, and others have reported it on this board and other places. It does make determining the kind of fluid that is installed a little more challenging if one is not the person who rebuilt the system. But there are simple tests to determine if the fluid id DOT5 or glycol based.

[John D.]

Re: Silicone or Dot 3 Brake fluid

I have had DOT 5 in my 67 for almost twenty years with zero problems. Does anyone have access to SAE technical paper 860633 ? It covered the issue of residual glycol brake fluid in the conversion of Army vehicles to silicon. If I remember correctly the minimal glycol based fluid left after flushing the system had no impact on brake system performance since the two do not mix.

[Terry M.]

Re: Silicone or Dot 3 Brake fluid

I have had DOT 5 in my 67 for almost twenty years with zero problems. Does anyone have access to SAE technical paper 860633 ? It covered the issue of residual glycol brake fluid in the conversion of Army vehicles to silicon. If I remember correctly the minimal glycol based fluid left after flushing the system had no impact on brake system performance since the two do not mix.

I have it here someplace -- along with a couple of other SEA papers about DOT5. As I remember the Army tested DOT5 conversion practices over a long term (ten years, I think) in the Panama Canal Zone.

There was a time when Dow Chemical, one of the manufacturers of DOT5, recommended simply flushing the new DOT5 through the brake system. I have some containers from the late 1960s with that recommendation printed on them. That method resulted in a black sludge in the brake system. It appeared to not affect the system adversely, but was regarded as undesirable none-the-less. The end recommendation was to flush the system and rebuild the components to eliminate as much of the residual glycol fluid as reasonably possible.

[John H.]

Re: Silicone or Dot 3 Brake fluid

I Think leave the dot 5 to the euro.cars ( BMW Mercedes)

Ed -

BMW and Mercedes don't use DOT5 silicone fluid; there isn't a car on the planet that uses DOT5 silicone fluid as factory fill.

[Peter J.]

Re: Silicone or Dot 3 Brake fluid

I did my 66 with Dot-5 in 1995 or 96 with my newly sleeved M/C, new brake lines and rebuilt and sleeved calipers and have had no issues with they them at all.

[Terry M.]

Re: Silicone or Dot 3 Brake fluid

Ed -

BMW and Mercedes don't use DOT5 silicone fluid; there isn't a car on the planet that uses DOT5 silicone fluid as factory fill.

Harley did/does use DOT5 and the only other DOT5 users are military vehicles. Modern cars can't use it due to their anti-lock brake systems. And most wouldn't use it anyway since the cost is higher than glycol and they only care about the car through the warranty period. Most of us are long past that.

BTW: New Corvettes use DOT 3 for the brakes and DOT 4 for the clutch. The clutch is exposed to more heat than the brakes (unless you track the car) thus the DOT4 there. And that specification is all bout cost.

[Richard R.]

Re: Silicone or Dot 3 Brake fluid

Jeff I had my calipers SS sleeved in 1988 and went back with Dot 5 with no problems. The one advantage is, it is not water soluble. Dot 3 mixes with water very easily and is the reason to use SS. There was an article some years back about a fellow member taking his car to Denver and when reaching the higher elevatios he had no brakes. Seems like if you have the least amount of air in your system it is magnified. Hope this helps Reed

[Patrick T.]

Re: Silicone or Dot 3 Brake fluid

One thing I'll mention is that any glycol brake fluid will destroy the finish of any paint it touches. DOT 5 is silicone and won't harm the paint in any way. Ask me how I know! I've had DOT 5 in my car for 11 years and never had a single problem.