I agree with Kevin on this one..
I use silicon fluid as well in The MGB and my Go Fast V Twin road bike...( go fast? Ya need to be able to STOP fast )
I have a pistol grip hand pump for One Man brake jobs.. Moss Motors, among others, Carry them..The silicon fluid is readily very available .. at least through most British car parts suppliers..
Silicone fluid is labelled DOT 5 here in the states.
Be careful using it in ABS cars (most everything new)...since DOT5 has different compressibility than the earlier fluids, you have to make sure the ABS system is compatible. Definitely a dealer question. Not an issue with surge brakes on trailers, since there is no ABS.
kmclemore wrote:Actually, Rich, not all brake fluid is hygroscopic. Silicone fluid is highly resistant to water absorption, and that's why I use it in all my vehicles. However, you *must* purge the system of all other fluid before installing it... the two don't mix well.
(And yes, you *can* use it in British cars with Girling or Lockheed systems, despite what others may say - I've done it for many years with great success).
I'll deffer to your expertise in the area, sir. My familiarity ends with DOT 3 fluids of the past decade. My understanding was, that the fluid absorbed the moisture to keep it from corroding the brake parts. Mea culpa.
~Rich
dot 3/4 is hygroscopic but works well if maintained. silicone is great but is a lot more compressible..absorbs more air (can cause poor pedal feel compared to dot 4). Can't (or shouldn't) be used in ABS cars, and other drawbacks.. Silicone is not the solution to all cars. Silicone is IDEAL for classic British cars that are not driven hard (raced/etc). I would consider it for my BGT (street driven), but still use DOT4. My 80 B I also use DOT4 due to occasional racing/autocrossing.
I will take the occasional brake flush of DOT4 over the significant drawbacks of silicone DOT5. I would never consider DOT5 for M trailer brakes..You want as much incompressible fluid as possible to actuate the calipers on the discs...and the heat the brake pads will transmit back to the brake fluid. Drum brakes is less of an issue, but I would stick with DOT3/4 for Mac brakes.
DOT 4:This brake fluid is also based upon poly glycol. Its dry boiling point (ERBP) is 230°C minimum and wet boiling point (Wet ERBP) is 155°C minimum. It is used in medium and higher size of modern cars; and also for vehicles in high-altitude, towing, high-speed braking situations or ABS systems. This brake fluid does not require cleaning the system and it can be mixed with DOT 3,DOT 5.1 without damage to the system. This brake fluid also absorbs moisture out of the atmosphere thus reduces its boiling point (ERBP). It can also damage the paint on a vehicle. The modified poly glycol boric ester DOT4 brake fluid is also available.
DOT 5: This brake fluid is based upon silicone. Its dry boiling point (ERBP) is 260°C minimum and wet boiling point is (Wet ERBP) 180°C. It is used in applications, like for weekend, antique, collector cars that sit for long periods and for some military vehicles. Some car manufacturers are also used in their road driven vehicles. This brake fluid does not mix with DOT 3, DOT 4 or DOT 5.1. It will not absorb water and will not damage the paint on a vehicle. It is also compatible with most rubber formulations. It absorbs more air and giving poor pedal feeling. It is unsuitable for racing due to more compressibility under high temperatures. If as little as one drop of water enters the fluid, severe localized corrosion, freezing or gassing may occur. This can happen because water is heavier and not mixable with silicone fluids thus it is unsuitable for ABS.
DOT 5 fluid is highly compressible due to aeration and foaming under normal braking conditions, providing a spongy brake feel. Poly glycol type fluids are 2 times less compressible than silicone type fluids, even when heated.
Catigale wrote:Silicone fluid is labelled DOT 5 here in the states.
Be careful using it in ABS cars (most everything new)...since DOT5 has different compressibility than the earlier fluids, you have to make sure the ABS system is compatible. Definitely a dealer question. Not an issue with surge brakes on trailers, since there is no ABS.
True, but I would prefer the least compressible fluid (dot3/4) in trailer brakes for the least amount of actuator movement, firmer feel, faster acting. Much more important with disc (M) brakes than drum (X) brakes as the fluid will get a lot hotter with disc brakes due to their design (BAD for silicone fluid).
This has been a great discussion to follow.
As Uncle Jim mentioned a few pages back, I too, used to have little one-man-bleeder tubes that had little check valves in the end of them - about 8 inches long or so. You would slip one end of the little clear tube over the nipple and it had a plastic "snap-in-place" holder to keep it locked on. Then you could twist open the bleed nipple and leave it that way, putting the little check valve end of the tube down in a jar or something to catch the brake fluid. Then you go and steadily pump the brakes, stopping to top off the reservoir as you went. When finished, you would just tighten down the bleed nipple and take the hose off.
Don't remember what they were called, but they were not expensive, and got them at the auto parts store...and for a kid on a budget who couldn't afford expensive fancy tools, they were a life-saver!
As far as brake fluid to use - the only fluid that is not compatible with others is DOT5. This is the older full synthetic fluid (good high heat, extreme conditions, used for race cars etc.). DOT3 is the old fluid many of us grew up with and is very hydroscopic (attracts water) and is bad because brakes hydraulics corrode. DOT4 is the LMA type (low moisture absorption) and is great for any brake system. A newer fluid is DOT4+ and this is a synthetic LMA that is compatible with non synthetic fluids. IMO, look for a synthetic DOT4 (DOT4+) and will be great for any system. In my cars I use ATE Ultra Blue, This fluid is blue but also has an amber equivalent. The first time you bleed brakes, use the blue and bleed until the blue fluid appears. The second time, use the amber.
As far as volume, a pint is plenty (as when my brake line broke at the caliper due to a bad factory choice of fittings on the new trailer - did I mention how awesome the brakes are on my car, able to stop the boat and trailer on the highway when we hit bad traffic ).
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due to a bad factory choice of fittings on the new trailer - did I mention how awesome the brakes are on my car, able to stop the boat and trailer on the highway when we hit bad traffic 
).