i built my car about 12 years ago and only have 4000 miles on it. I want to top off my master cylinder but forgot if I had used DOT 4 regular or DOT 5 silicone. Is there any way to tell which one I used? You know like touch, smell, etc....... I went back thru all my receipts I kept on the car and it looks like I purchased both and for what reason I don't know. Peace, Chaz
There is probably some chemical test you can do, or just dump one in and maybe it will be the right one. Did you own something at the time that used silicone fluid?
silicone fluid looks purple. It won't mix with water like normal brake fluid will. It won't eat paint like normal brake fluid will. Maybe you could take out a sample, and see how it behaves.
I think the color, as Jim said, would be the biggest giveaway. Maybe the smell too. I have DOT 5 in mine but don't remember if it has that same distinctive odor as DOT 3. But the color should tell you. I think DOT 5 also doesn't make your hands all wrinkley like DOT 3 when you get it on them. Don
You have old dirty contaminated brake fluid. After that long drain and flush the system. Check all lines, rubbers, and hoses closely. Replace with whatever you want.
I just used DOT 5 last weekend. I don't recall it having any particular smell, but it does look like purple kool-aid. Also, wear gloves. You don't want any chemical absorbing into your skin.
That is one of the nice things IMO about DOT 5, it seems to stay nice longer in the system than DOT 3. When I rebuilt my 27 roadster about 4 years ago I drained out the DOT 5 that had been in there for 20 years and it came out looking like the day I put it in, clean as a whistle. The parts like the MC and wheel cylinders were rustfree too, but I replaced the MC just to be safe and rebuilt the wheel cylinders for the same reason. But the fluid itself was very clean when I drained it into a glass jar. Some people say it gives soft pedal and other issues, but it is all I run and I like the fact that it doesn't eat my painted parts if I spill any of it. Don
so that's how you tell which it is...if it looks nice, it's silicone, if it' looks grungy it's normal brake fluid.
Do not use DOT 5 unless your braking system is specifically set up for it. It erodes the seals of conventional brakes and you can lose all brakes without warning - that 'Oh shit' moment as the pedal goes to the floor. I nearly took the NSRA safety tent and personnel out years ago when I had this problem on a car I had purchased and subsequently found out it had silicone brake fluid installed. Few hot rod brakes are set up for DOT 5 and there is absolutely zero reason to use it on the street. DOT 5.1 on the other hand is NOT silicone based....
You don't want any chemical absorbing into your skin. Funny thing about this. Many years ago, probably mid 60's, I was working with probably DOT 3 brake fluid, and got some on my hands. I was always getting oil, grease, gas, everything on my hands. I remember it was mid 60's because I worked after work at a sevice station. Not a gas station or convieneint store, a real service station! I had several warts on my fingers which I sometimes nearly ripped off when pulling down those danged flip down license tags or tail lights to get to the gas cap. Long story longer, after a few days of the spilled brake fluid on my hands the warts were almost all gone. I put a few drops of brake fluid on the remaining warts and they soon disappeared. I don't recommend this and it may not be what got rid of my warts. But they remain gone to this day and I am still reasonably healthy and sane.
Right here^^^^ This is correct. DOT5 is for Harley's, since its gentle on paint and chrome. DOT5 does NOT mix with water and all brake fluids attract moisture. So you'll have pockets of water in your brake system that can over time rust parts of brake system from the inside out. As mentioned, DOT5 can destroy seals and lines over time if your parts are not compatible. DOT 3 and 4 do mix. Also, ignore dry boiling point, it's irrelevant in the real world.
I went out and ran a test after reading so far. This was basically what I found. I had some DOT 5 Silicone brake fluid but it was more of a amber-green tint to it, not purple. 1. Took 1 white plastic cup that had water in it and placed DOT 5 silicone brake fluid in it. 2. Took 1 white plastic cup that had water in it and placed some of my brake fluid in it from my Master Cylinder. 3. The DOT 5 Silicone fluid formed balls on top of the water. 4. The fluid from my Master Cylinder just sort of dissolved or dissipated into the water but sort of stayed together. Seems that I must have a NON-Silicone brake fluid in it even though I can't go by color. What do you think? Peace, Chaz
Dot 5 is nice to your paint,..... My personal experience with it my then new 84 F250 was that for some reason or other, extensive brake use at higher elevations would result in a rather soft pedal. Bleeding the brakes revealed air in the system. This happened more than once, and long after changing over from dot4, so it wasn't that I left some air in the system. Someone wrote in a magazine tech section that silicone brake fluid had a tendency to do that. Has anyone else heard of this,...or had a similar experience ? The problem vanished, upon changing back to DOT 4. 4TTRUK
I have to respectfully disagree. We have used DOT 5 exclusively for the past 25 years with zero issues. Right now we have 3 cars with it, soon to be 4. Like I mentioned in the previous post, when I tore the car apart after 20 years the bores on the wheel cylinders were spotless and all the rubber components were still sealing tight. In fact, in 20 years I had never added one oz of fluid to top it off. Like every other subject, we all have different opinions and experiences, that is just what I have experienced. Don
i've had the same dot 5 in my `28 tudor since i bleed the brakes about 20 years ago. i just checked the level in the MC this week and it looks fine and the brakes work great with no leaks
Sounds like you have regular brake fluid. Still wouldn't hurt to crack the bleeders and flush new clean Dot 3 or Dot 4 through it. Twelve years is a long time.
Despite your experience, every major automobile manufacturer who used DOT 5 when it first came out has now ceased to use it because of all the problems and it's ultimate poor suitability for road going vehicles. If you look at a can of DOT 5 on the shelves of the auto parts stores it has strong and specific warnings about it's use. DOT 5 works in race cars which are regularly maintained and have brake systems set up to use DOT 5. But, from personal experience of total and sudden brake failure in a well set up brake system that simply was not equipped to use DOT 5, it suddenly no longer seemed like the wondrous cure all elixir for braking solutions. There have been many things that have seemed like a good idea - some of the vociferously mandated by government - but later proven to be not as good or safe as they were heralded to be - to wit MTBE and Ethanol. To my mind DOT 5 belongs to this category. Life is about choices and the risks we choose to take. Cigarettes are known to cause major health problems for example, and yet people still choose to smoke. So feel free to make your choices and I'll make mine. DOT 5 is not one of my choices....
I understand. All I can base my opinion on is what it has been like for me personally. I would use DOT 3, but I don't want it eating up my painted surfaces, and no matter how careful you are some will get on them. So I pay a little extra and if it gets on the paint it makes it shinier. Don
The Jalopy Journal
