I have replaced or rebuilt every hydraulic component on the Speedster. Both the brake and clutch systems are dry.
My question is what DOT fluid would you put back into the systems? I'm leaning toward DOT 5, but I welcome and respect your opinion.
THANKS,
Jody in Tallahassee
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If you go DOT5, you can always go to 3 or 4 should you change your mind. If you go with DOT3 or 4, you can 't go to 5.
Next car, I'm going DOT5 for sure.
I would go with DOT 4
DOT five is more for racing conditions and expects to be replaced more frequently. It has a slightly higher boiling point (360°, I think) versus DOT 4 at around 310° but neither will ever get hot in a street car.
That said, either will work fine in a street car. Choose the cheaper stuff.
DOT5 is silicone based and not hygroscopic. It doesn't attract moisture. It's non-corrosive. If you put DOT5 in the system, you can leave it there. It's quite a bit more expensive than DOT3 or 4.
There's almost zero substantive difference between DOT3 and DOT4. If I were going in that direction, I'd use the 3.
But, from everything I've read, I'd go with DOT5.
If the system is NEW, and I mean NEW, and all components are bone dry and clean, I'd be inclined to use DOT5.
If any part of the system is used, like the metal brake lines, I'd just go DOT 3/4(usually labeled as such, I use Valvoline Synthetic 3/4) and change it every 2 years like you're supposed to. The problem is nobody changes it. Come to think of it, I built my Spyder in 2017 and didn't flush last year, as the engine and trans got rebuilt last summer. So it's on my to-do list for this spring.
DOT 5 is NOT compatible with even a trace of regular brake fluid.
Good info to know about change overs Danny... I just did a full changeover to Dot 3 Thanks
Thinking of changing fluid intervals, I used Evans coolant in my Roadster/Subie for life time no change needed. It would be nice if hydraulic fluid had an option as well for longer life seeing no one every changes it in a DDriver.
DOT5 requires longer pedal travel to compress the fluid. I'd just go with DOT3 and change it out every couple of years.
Or just leave what'cha got in there like all of us do in our daily drivers for 10 - 15 years.
Jus' Sayin'..........
I mean...... Do you think and anyone ever changed brake/hydraulic fluid in an old Volkswagen Beetle during the life of the car?
Nobody ever changed brake fluid in their drivers back in the day. But everybody rebuilt their brake cylinders, pretty much every couple of years.
I’ve gotten into the habit of changing fluid every few years since I started taking the car to the track.
Gordon Nichols posted:Or just leave what'cha got in there like all of us do in our daily drivers for 10 - 15 years.
Jus' Sayin'..........
I mean...... Do you think and anyone ever changed brake/hydraulic fluid in an old Volkswagen Beetle during the life of the car?
But that's why they had to replace or rebuild all the hydraulic parts, MC, and wheel cylinders. If you change the fluid every two years, you don't have to replace anything, except hoses that dry up and crack.
THANKS everyone for your inputs.
Danny is imparting wisdom here.
I am thinking of changing my brake fluid. Is there such a thing as colored fluid or dye so I can tell when all the old fluid is out?
One reason I am thinking of doing this is because I want to replace the switches on my master cylinder. I am assuming it is necessary to bleed the brakes after doing this, right?
With the switches at the bottom portion of the M / C remove the old one and promptly replace w/o bleeding. ....as for fluid dye there is old dark and new clear :~)
Thanks Alan!
Ya know Michael, that's a really good idea about having different colored brake fluid that's compatible with each other ! Say like, clear, blue, red, and green that way you would know when you've really bled all the old fluid out !...................Bruce
There was a blue ATE fluid but it is no longer sold in the United States.
I concur with Alan the old is dark and the new is clear so it is evident when you do it.
ATE Super blue. its DOT4, don't let it get on your skin. It burns and gets hot within seconds. Think Icey hot on steroids Ask me how I know. On track cars I go with Super blue, and then change it next to ATE amber DOT4 its easy to see when you have the old out and the new in the system
I started using Motul 5.1 on my bikes and I'm in the process of changing everything else over to it. Unlike Dot 5, it's compatible with DOT 3/4 but has the added bonus that it's not corrosive to automotive finishes.
I would have done it last summer, but my Motul distributor went out of business and I haven't found anyone else that can supply me a 5L can. It's $11/.5L, so buying it in quantity is a must. I'm redoing the brakes n the Spyder and need to flush the 968 and the ML and Smart as well.
@Tab Tanner, is the ATE Super Blue available in the US? What I have read seems to indicate it no longer is.
@dlearl476 Amazon has the Motul 5.1
DOT 5.1 has the same negatives as Dot 3 or 4. It will absorb water AND is corrosive to painted surfaces. It is glycol-based, which is why it is compatible with DOT 3 or 4.
Do not make the mistake of putting in 5.1, and then thinking you no longer have to change your brake fluid.
The benefit of 5.1 is that it's boiling point is higher than DOT 3 or 4, and has about an equal boiling point to silicon-based DOT 5.
I not 100% sure if ATE blue is still available in the US. I have a few cases of it on the shelf.Ill check with my supplier and let everyone know
It is interesting that, on Amazon, 2 Motul 5.1 are only a bit more than $4 than one. Amazon also has a synthetic Motul 4. I wonder if it absorbs water.
Bosch ESI6-32N Brake Fluid on Amazon is also interesting.
i heard U dont want to mix DOT 3/4 with 5 as they dont mix and its hard to flush out the 3/4
No 5 but 5.1 is OK with 3 & 4.
Here's a nice write up on brake fluids and a good source too.
I just bought a brake fluid tester on Amazon. I tend to neglect flushing my brake fluid on all my cars. On the other hand, I don't want change it if it is still OK.
Just about all manufacturers state that every 2-3 years, fluid should be flushed/replaced.
Just do that, and you needn't worry. Maybe Ray was right to get the fancy-shmancy pressure bleeder! I know I'm not having a shop do it $$$
@Gordon Nichols posted:@dlearl476 Amazon has the Motul 5.1
Everyone has the 5.1, in .5L bottles. I have 4 cars and a motorbike to do. That's why I want a 5L can, which no one has. I'm going to check with one more retailer here in town tomorrow and if they can't order it, I'll throw in the towel and use Ate or Pentosin, both of which are available in 5L cans from Pelican and ECS.
@DannyP posted:DOT 5.1 has the same negatives as Dot 3 or 4. It will absorb water AND is corrosive to painted surfaces. It is glycol-based, which is why it is compatible with DOT 3 or 4.
Do not make the mistake of putting in 5.1, and then thinking you no longer have to change your brake fluid.
The benefit of 5.1 is that it's boiling point is higher than DOT 3 or 4, and has about an equal boiling point to silicon-based DOT 5.
I've been using 5.1 in my bikes since ~2005 and I've never had it damage a painted surface. And with the tiny reservoirs on the handles bars, it's nearly impossible to fill/bleed a system without getting at least a drop on a painted surface no matter how careful you are.
If you wash it off it won't damage the paint, Dave. You just have to do it right when you spill it, not days later.
I have a Motiv pressurized tank and Gordon made one by himself 
My cap did not work out well so I had to gerryRig it but I managed it. Honestly, it was not a big job and I bought a 1 Liter and an extra 500ml that is left unopened. I think it is doable at a more consistent pace with this set up. An extra pair of hands, or feet should you need to pump the pedal, is really nice to have.
I also have this pressure bleeder. It worked very well for me. The bleeder comes with a cap specific for your car's fluid reservoir. I had no problem with the cap. I want to get caps for my other cars.
Those pressure bleeders work great; a friend of mine got one:
