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I'm getting the brake system together on my '63 Dynamic 88.
The cylinders, hoses and lines are all new with no fluid in them.
I'm undecided as to whether to use regular DOT 3 brake fluid or silicone DOT 5 fluid.
I would like advice and experience using either type of fluid.
Charlie, I used DOT 5 silicone after rebuilding my brake system. Here's my wisdom...
It is difficult to bleed because it easily incorporates bubbles when done traditionally (press the pedal). I found that gravity bleeding worked well. For the rear I had to raise the front about 6 inches to get a better angle. It took about 2 hours for fluid to come out the right rear bleeder.
I had ongoing problems with leakage at the flare joints. This was mostly operator error. I double flared the stainless lines, which made it too stiff to conform well to the flare seat. I eventually used copper washers in each problem flare joint. These are purpose-made for this problem and are available in the sizes you need. They are soft enough to act as a gasket.
Do all your frame and detail painting before adding fluid. Silicone is difficult to remove completely from surfaces and interferes with paint adhesion and finish. I used naptha wash to remove the silicone. Some silicone got inside the frame rails and would seep out through openings and lap joints shortly after cleaning the exterior of the frame. I made a spray tube to deliver the naptha inside.
After completion, I have been very pleased. No problems after 16 years.
5 is nice because it doesn't eat paint. But you have to be careful not to cross-contaminate for the life of the brake system.
You can use 5.1 to get the higher temp rating in a "traditional" fluid. The Bosch fluid is available affordably on Amazon, too. I just keep a hose handy when doing anything exciting, like pressure bleeding. Douse a brake fluid spill with water and it'll neutralize the fluid before it eats anything.
Brake fluid was designed originally to absorb water to avoid puddles in the lines which greatly degrade performance. Silicone fluid won't absorb water. I would rather have to change the fluid periodically and use Dot 3 or 4.
Thanks guys.
DOT5 it will be.
I know that DOT5 doesn't absorb moisture like regular DOT3.
That's important in this very humid state of Florida.
Just wanted to see if there were any downsides to it.
I recommend the DOT5.
I've had too many brake issues from cars sitting for extended periods of time.
I have it in 4 cars with no issues, with more to follow as the need arises.
1 has been converted for 30 years now that also traps at 132mph in the 1/4 & it stops just fine.
DOT5 is also standard issue in many military vehicles, so it isn't something which hasn't been put to extensive testing.
Here is a picture of the wheel cylinder pistons out of my 5 ton, from an unknown duration.
Yes, it holds a lot of fluid...
As for bleeding, gravity works ok.
Vacuum works well to pull it through the wheel cylinder/caliper if you have issues with gravity bleeding.
FYI when it ages, it turns from purple to yellow but still works well.
It is completely compatible with older brake systems and DOT 3 and 4 fluid, but has a higher boiling point than even silicone fluid. You don't have to worry about flushing every last bit of the old fluid out of the system. Pricing of 5 and 5.1 is about the same.
I'm really liking DOT 5.1. It is not silicone and it is backwards compatible with DOT 3 and 4.
The DOT 5 Composition says silicon. That’s a hard glass-like element that semiconductors are made of. I see lots of breast implants are erroneously claimed to be made of the same substance. That’ll poke your eye out.
