15

Standard automotive brake fluid (DOT 3,4 and 5.1) are made from polyethylene glycol (PEG). PEG is soluble in water, methanol, ethanol, acetonitrile, benzene, and dichloromethane, and is insoluble in diethyl ether and hexane. A long way of saying it will clean up with soap and water. DOT 5 brake fluid is diorgano polysiloxane (Silicone). It is not soluble ...


13

There is no difference between the two. To replace it, you have to flush out the old brake fluid with new fluid. See this answer on how to bleed brake lines for more details.


12

The piston is hold in place by a rubber-gasket. The piston does not slide in this gasket, instead, they stick together. So, when the brake is activated and the piston moves towards the disk, the gasket deforms a little to allow this movement without sliding. When the brake is released, the gasket moves to its original shape and retracts the piston. ...


11

If you lost all (or almost all) of your brake fluid, you have a leak. Check all of your calipers (assuming disk brakes all around) to see if there is a leak at the wheels. If none there, check the soft lines (rubber lines at the wheel) for leaks. If no leaks there, check around the master cylinder and anti-lock brake unit for leaks from the lines. If you do ...


11

Not having brake fluid in your car won't destroy the brakes, but whatever you hit when the brakes don't work just might. :) The brakes in basically every passenger car since the 50's are hydraulically operated. That means when you press the brake pedal you are pressurizing some fluid lines. Those lines run out to the wheels where the added pressure forces ...


11

tl;dr: You are doing a better job than most, and as a result reducing your chemical footprint further will largely require being more proactive about safe chemical disposal than most people are willing to be. Having said that, there are a few things to consider. Reduce the amount of waste that you generate where possible. The best thing I can suggest for ...


9

For everyone's edification, here are the dry/wet boiling point specifications for the different brake fluids: Dry boiling point Wet boiling point DOT 3 205 °C (401 °F) 140 °C (284 °F) DOT 4 230 °C (446 °F) 155 °C (311 °F) DOT 5 260 °C (500 °F) 180 °C (356 °F) DOT 5.1 260 °C (500 °F) 180 °C (356 °F) Why ...


9

Depending on the car model and the technology used, not all fluids I mention here do exist. Here is list of all that I know of: fuel (some cars use two typed of fuel, e.g., petrol and gas, so they have two fuel tanks) engine oil two-stroke oil (in some systems the oil is separated and only combined in the injection) gear oil Automatic Transmission fluid (...


9

Dot 3 and Dot 4 are mixable, you can use whatever you want. Just do not put Dot 5 into it, thats a whole different thing and not mixable with Dot 3 or Dot 4.


8

Check Brake Fluid on Wikipedia. DOT 5 is not interchangeable or compatible with DOT 3, 4, and 5.1 fluids and can cause catastrophic system failure. Dot 3, 4, and 5.1 are glycol ether based. They are compatible, but like motor oils, you should use the recommended or higher grade fluid. Dot 4 and 5.1 also have borate ester to handle higher temperatures. DOT ...


8

The information & links posted by Paulster2 offer excellent explanation of what the various types of brake fluid are. There are a few grade : DOT3 DOT4 DOT5 DOT5.1 The difference between them is a specificed standard regarding the boiling temperature, which rises as the DOT number rises, and amount of water absorption. There are based on two ...


8

The biggest advantage to DOT5 brake fluid is that it is hydrophobic meaning it doesn't like water. This is in contrast to DOT 3, 4, 5.1 which are hygroscopic which means it will absorb water even just out of the air. This is a huge advantage if storing the car for most of the year and only breaking it out a few times during the summer. If using any other ...


8

Based on what you have posted, changing the brake fluid is not going to solve the problem. It's just going to provide a clean new fluid to boil when your brakes stick. If I read what you said correctly the guys at the garage are telling you that the brake cable (likely the emergency brake cable) on the rear is what's causing the rear brakes to stick. They ...


8

Any sort of brake fluid leak is a serious issue which needs to be fixed for several reasons. Any fluid leak means that air is also getting into the system which will accumulate and degrade braking performance. A small leak could turn into a sudden complete failure suddenly and without warning. As well as the obvious safety issue a sudden failure will be ...


8

There's one slight problem with your theory. The fluid which goes out to the brake cylinders/calipers stays out there. It will never come back to the master cylinder. You have to do something to remove this fluid. The only way is to flush it out. The biggest issue with all of this is the brake fluid which never comes back and stays in the lines will absorb ...


8

Short answer: It gets REALLY hot - like, way over 100C (decimal). And, as @SolarMike's answer states, the water that the fluid absorbs from the atmosphere likes to vaporize under those conditions. Brake systems are technically closed, sealed systems, but no seal is perfect. Put another way: Heat in the engine bay is a non-issue for brake fluid. All of the ...


7

I found this description of synthetic based brake fluids. According to the page, all brake fluids are technically "synthetic" in that they are man made and do not contain a petroleum base. "Synthetic" brake fluid, as we think of it, has a silicon base. Non-synthetic brake fluid (normal brake fluid) is glycol based. There are trade offs to each type. Silicon ...


6

Prestone does make product that is compatible with DOT3 and DOT4 fluid referred to as DOT3/4. Several sites state you can use 4 in place of 3. However using 3 in place 4 may decrease brake performance. Without knowing the year it is hard to tell which is the most correct type of fluid for your Toyota. Regardless of the type used, that is the lesser of your ...


6

As R.. says, the remaining softness will be down to air in the lines - this can be fixed by properly bleeding the system. Before you do that, however, you need to establish the cause of the loss - until you do so, the car should be regarded as dangerous and must not be used. If you're in any doubt, take it to a professional. The most likely cause of a ...


6

tl dr - Mixing Brand X fluid with Brand Y fluid is of no consequence, as long as you are mixing the same grade of fluid (DOT3, 4, 5, or 5.1). In order to be rated at a given grade, it must meet the prerequisites of the grade. This has to do with wet/dry boiling points, not who makes it. With that said, you can mix DOT3, DOT4, or DOT5.1 together (each of ...


6

There are quite a lot of different fluids inside a modern car. I tried to group them by purpose. Hydraulic Fluids General use: Hydraulic fluids are used to transfer power from one point to another Brake Fluid - Based on glycole-ether, mineral oil or silicone oil. Brake fluids are designed to have high boiling points because the brake system is subject to ...


6

It sounds like your clutch master cylinder is initially letting fluid past the piston seals. Pumping the clutch pedal sounds like it gets the piston sealing again so that the clutch starts to work. I am presuming that the clutch and brake both share the same reservoir and that you are not loosing fluid and not having to keep filling it up. Is that correct? ...


6

If your brake pedal went to the floor it means that there was not enough hydraulic pressure to apply the brake. If they were working fine before and never felt squishy then your master cylinder has probably gone out and needs to be replaced. Alternatively you may have a lot of air in the lines, enough that the pressure applied by the brake was not enough to ...


5

Two things to look for. 1) air in the brake fluid. 2) incorrectly assembled brake pads, especially the anti noise shims. Air in the brake fluid is the most common cause of low, spongy brake pedal feel. Moisture in the fluid will not substantially change the pedal feel until the fluid temperature exceeds the boiling point of any water in the fluid, then ...


5

Yes. When brand new, brake fluid looks clear. Once there is a significant amount of water absorbed, it will turn an amber color. This applies to regular brake fluid (DOT 3, 4, & 5.1) and not synthetic. Here is an image of new and old brake fluid: As you can tell, it gets darker as it gets older.


5

It seems as though the plunger in the master cylinder isn't retracting after use Occasionally when motorcycles are stored you can run into this problem. Older brake fluid along with a bit of moisture and oxygen can contribute to a buildup of material inside the master cylinder bore where the plunger goes. After pulling the brake once the plunger sticks ...


5

When buying a used car it's usually a good idea to change all fluids, just so you know exactly when they were changed, and can start your own fresh service history. This may be part of the reason why the dealer recommended these services. Like almost any other fluid used in a car, time, environment, and use will eventually cause degradation and decreased ...


5

YES. A big Y-E-S. It's a huge safety issue. See, braking fluid absorbs(even attracts) water over time, not so much over usage, if at all. Brake fluid gets really hot, even more under sustained braking like when driving in the mountains. If there's water in the system, it'll try to evaporate. This causes vapor locks, pedal/braking pressure falls away, etc. ...


5

If your caliper has any brake fluid coming out of it, it's time to rebuild/replace the caliper. There should be absolutely no fluid loss anywhere in your braking system. If it is leaking at the caliper, not only is the caliper failing, but if the brake fluid gets on the rotor/pads, it won't provide much in the way of stopping, either. This is a huge safety ...


4

The Astra H has a concentric clutch slave cylinder which means the gearbox has to be removed to replace it, 5 to 6 hour job. Try holding the clutch pedal down on the floor, engine idling - car in first - handbrake firmly on. Just keep it held down for a while and wait. If the slave is faulty, after a little time the clutch will try to take up the drive and ...


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