Buick35 Posted November 10, 2023 Share Posted November 10, 2023 (edited) Can silicone brake fluid be added to regular brake ? Edited November 10, 2023 by Buick35 Spelling (see edit history) Link to comment Share on other sites More sharing options...
Fordy Posted November 10, 2023 Share Posted November 10, 2023 No, the system needs to be thoroughly flushed and cleaned out. Even DOT5.1 is incompatible with DOT5. Steve 4 Link to comment Share on other sites More sharing options...
nat Posted November 10, 2023 Share Posted November 10, 2023 12 minutes ago, Buick35 said: Can synthetic brake fluid be added to regular brake ? Sure, just pour it in. Unless you are a chemist, the safe bet is to never mix different fluids/lubricants. What the heck is "synthetic brake fluid"? Link to comment Share on other sites More sharing options...
Fordy Posted November 10, 2023 Share Posted November 10, 2023 5 minutes ago, nat said: What the heck is "synthetic brake fluid"? Silicon based as opposed to what has been used for years - won't eat paintwork is its real only benefit other than a higher boiling point. Link to comment Share on other sites More sharing options...
dictator27 Posted November 10, 2023 Share Posted November 10, 2023 54 minutes ago, Fordy said: No, the system needs to be thoroughly flushed and cleaned out. Even DOT5.1 is incompatible with DOT5. Steve All rubber parts should be replaced, including hoses. 1 Link to comment Share on other sites More sharing options...
zepher Posted November 10, 2023 Share Posted November 10, 2023 Also, be aware that using silicone brake fluid will result in a spongier pedal feel than regular brake fluid. I use silicone fluid in my motorcycle, but I was warned about the spongy feel and the need to completely flush the system to remove all traces of previous fluid. Link to comment Share on other sites More sharing options...
Bloo Posted November 10, 2023 Share Posted November 10, 2023 (edited) Now this is getting REALLY confusing..... The main advantage of *Silicone DOT 5.0* fluid (other than the boiling point) is that it is not hygroscopic. It does not draw moisture from the air. Actually this is kind of a big deal on older cars with systems vented to the atmosphere. Silicone (DOT 5.0) brake fluid should not be added to Glycol brake fluid (DOT 3, DOT 4, DOT 5.1). Every can of DOT 5.0 Silicone I can ever remember having says it's OK to mix the two, but there are horror stories on the web of the mixture gelling up and things like that. I don't know if I believe it or not. It doesn't matter though. Either way, you should not mix Silicone (DOT 5.0) with Glycol (DOT 3, DOT 4, DOT 5.1). Silicone fluid is difficult to bleed. It also floats on top of the glycol, and therefore never gets to the bottom where all the corrosion damage is happening. Since the remains of the Glycol fluid and water remain in the lowest parts of the system, you don't get to take advantage of the higher boiling point of the Silicone. In short you get all of the disadvantages of both types, and none of the advantages of either. Sponginess is air. Silicone (DOT 5.0) is *extremely* difficult to bleed. You might need to spread the process out over 2 or 3 days. Some never accomplish it. In my opinion, anyone who is going to try Silicone (DOT 5.0) should start with new hoses, all new rubber in all cylinders, and lines flushed with alcohol. There should be no trace of glycol left anywhere in the system. 3 hours ago, nat said: What the heck is "synthetic brake fluid"? The fact that we even have to ask this really annoys me, but we do. I was surprised the first time I got a can of "**synthetic brake fluid**" (not **silicone**). I felt I had to figure it out before adding a completely new unknown fluid to a brake system. It really took a lot of digging and time spent to get a straight answer. So it turns out that synthetic brake fluid is ordinary Glycol brake fluid. All conventional Glycol brake fluid is synthetic. Apparently two or three years ago the marketing people decided that "synthetic" sounded modern and high tech, and started printing that on the cans. Maybe they were planning to jack up the price. Who knows. It's the same stuff it always was. It's like saying "sugar free lettuce". Edited November 10, 2023 by Bloo (see edit history) 6 1 Link to comment Share on other sites More sharing options...
zepher Posted November 10, 2023 Share Posted November 10, 2023 7 minutes ago, Bloo said: Sponginess is air. Silicone (DOT 5.0) is *extremely* difficult to bleed. You might need to spread the process out over 2 or 3 days. Some never accomplish it. I have talked with people that race motorcycles and they are the ones that said in their race bikes they can tell that silicone is slightly spongy compared to regular brake fluid. These are privateers and factory riders for various professional race teams. I have found the same to be true with my street motorcycle. You hands are far more sensitive than your feet to the feel of a brake lever. 2 Link to comment Share on other sites More sharing options...
Bloo Posted November 10, 2023 Share Posted November 10, 2023 (edited) There is an extremely high probability they never got all the air out. My first experience with this stuff was back in technical college in the 80s. When I say it is difficult to bleed I am not kidding. It might be the understatement of the year. I converted my own car during that time. I was over a week bleeding it. Eventually I did get it right and got a rock hard pedal. One of my teachers was using it in his race car, and I got some pointers. I think I can do it in 2 days now, maybe, with planning and scheduling. It might take me three. I don't use Silicone fluid anymore, but may in the future. It solves the corrosion problem, and that is a big deal. On someone's first try with it in a car, I predict a week before it is bled, and that is if they know what to expect. If they don't know what to expect, it is going to take longer, and most likely they will never get all the air out and just give up. Just for fun sometime, put some in a glass jar. Pour some more in as if you were refiling a master cylinder while bleeding. now get your eyeball up to the jar and look. There are tiny air bubbles in there that were formed when you poured fluid. There are probably even smaller ones you cannot see without high magnification. Come back in three or four hours and look again. Yep, the bubbles are still there. Those bubbles get sucked back into the system if you go ahead and bleed right after you add fluid, or right after you just filled the system. Almost no one uses Silicone fluid in racing. You just can't be screwing around like this trackside like this when things go wrong. A quick bleed is going to be spongy, no question. Glycol on the other hand can be bled very quickly. Edited November 10, 2023 by Bloo (see edit history) 2 Link to comment Share on other sites More sharing options...
Frank DuVal Posted November 10, 2023 Share Posted November 10, 2023 I rebuild a brake system and fill with DOT 5 and get it bled in the same time as DOT 3. Never had an issue here at sea level. I've been using it for 40 years. Maybe I pour slower? ❓ I certainly do not shake the can!😁 🕸️🏎️🪡 4 Link to comment Share on other sites More sharing options...
c49er Posted November 10, 2023 Share Posted November 10, 2023 I have used a lot of silicone DOT5 in my old cars and in customers. Pour it slow ...bleed it slow....whether by pedal or pressure tank. Always use all new hoses and cups if installing DOT 5 if the system had 3 or 4. Flush or replace anything contaminated with the DOT 3 or 4. Never have had trouble getting a good firm pedal.. 2 Link to comment Share on other sites More sharing options...
Bloo Posted November 10, 2023 Share Posted November 10, 2023 @John_S_in_Penna, There have been posts edited, and that response isn't what it seems. It said "synthetic" not "silicone" previously. Yes you can mix synthetic with the ordinary kind, because it is the same thing. 1 2 Link to comment Share on other sites More sharing options...
drhach Posted November 10, 2023 Share Posted November 10, 2023 Other than not being hygroscopic, I think the other advantages to silicone are higher boiling point and not damaging to paint. I've used both in motorcycles over the years. My challenge has always been keeping it straight what I have in the system and keeping enough of both on hand because I have both in my different vehicles. If I didn't have a vehicle that specifically called out its use, I don't think I would bother changing over. Link to comment Share on other sites More sharing options...
Frank DuVal Posted November 10, 2023 Share Posted November 10, 2023 9 hours ago, c49er said: Pour it slow ...bleed it slow....whether by pedal or pressure tank. Yep. I once saw a person bleed a system (not using DOT5 thank goodness) and his foot on the brake pedal looked like a machine gun both in number of hits and force! Wham, wham, wham, wham, wham, OK open the bleeder he said to the other guy. Repeat many times. I shook my head and walked away. People like that are beyond teaching the proper way regardless of brake fluid type....😱 1 1 Link to comment Share on other sites More sharing options...
Paul Dobbin Posted November 11, 2023 Share Posted November 11, 2023 Drain the system of Dot3. Blow the lines out with air. Rinse the lines with alcohol. Add the Dot 5 & bleed. Enjoy 50 years of no brake fluid problems. Antilock brakes sensor may not recognize Dot 5, place black electrical take over the warning light. 1 Link to comment Share on other sites More sharing options...
Frank DuVal Posted November 11, 2023 Share Posted November 11, 2023 It's not the sensor lighting the light on ABS systems that is the big problem, it is the rapid fire application of the accumulator into the brake lines aerating the DOT 5 that is the issue. I will not use DOT 5 in an active ABS system. Active? Most of the AACA eligible vehicles already have frozen ABS parts from the DOT 3 that never gets flushed every two years as needed!😉 1 Link to comment Share on other sites More sharing options...
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