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19

If the manual is saying small amounts of DOT3 can be used, what they are most likely saying is if you find yourself with low brake fluid and only DOT3 is available, it is better to use that than to not have brake fluid. Once you get back home though you need to get the recommended DOT4 back in the system by bleeding the system and filling with DOT4. As ...


13

DOT4 brake fluid has a higher boiling point than DOT3, making the fluid less likely to boil. Using cheaper, lower-grade fluid increases the chances of your brakes failing in situations where they build up lots of heat, e.g., driving down a mountain on a twisty road. More information: http://www.carbibles.com/brake_bible_pg2.html


12

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.


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

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 ...


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 ...


8

Most people realize that brakes work by turning kinetic energy into heat. The brake rotors and pads get very hot, this heat is transferred to the brake fluid as well, if the brake fluid gets too hot and boils it effectively puts air in the lines and will lead to brake failure. You can put DOT 4 in place of Dot 3 but not the other way around. Note DOT 5 is ...


8

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) ...


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 ...


7

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. ...


7

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 ...


7

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 ...


7

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 ...


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

The main difference of DOT3 and DOT4 is boiling point of the fluid. The DOT3 standard has a lower minimum boiling point requirement then DOT4. Not all fluids are made equal and they will all typically list what both their Dry and Wet boiling points are. You can have one DOT3 fluid that just barely makes it past the standard, then another that can handle ...


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? ...


5

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 ...


5

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 ...


5

Not all sure how much of this is true but info I so far know and go by, DOT 4 has a higher boiling point and also has borate esters. DOT 5 is silicone based This is the dry boiling point minimum as I know of; DOT 3, 205 C (401 F) DOT 4, 230 C (446 F) DOT 5, 260 C (500 F) DOT 5.1, 270 C (518 F) In Australia DOT 3 is supposed to have min 230 C ...


5

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 ...


5

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 ...


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 ...


4

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.


3

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 ...


3

Sounds like a leak or a burst hose or pipe. Modern braking systems have a safety feature that lets you use some brakes even if a hose burst, so that would explain why only the front brakes seems to take. (https://en.wikipedia.org/wiki/Hydraulic_brake#Component_specifics) the FMVSS Standard 105, 1976; requires the master cylinder is divided internally ...


3

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 ...


3

Brake fluid by nature is hygroscopic, meaning it absorbs water. Even though it is considered a closed system, it doesn't mean it isn't hermetically sealed. Brake fluid will absorb water, have no doubt. You should change your brake fluid once a year or there about. As the brake fluid absorbs water, it becomes less tolerant of heat, meaning it boils at a ...


3

I agree with @HandyHowie in that it sounds like your clutch master cylinder is on the way out. Something to check before you go this route, though, is the hydraulic fluid level for the clutch. Looking at the parts involved, it looks as though while the master cylinder reservoir is remote (not attached directly to the master cylinder), it doesn't pull fluid ...


3

What hardware if any should be replaced every time the brake line comes off the caliper? I know there's a brass washer for the banjo bolt, but what is the criteria for replacing it? New/re-furbished calipers should include new washers. Always replace them when changing a caliper or line. I'm going to do pads on both sides of the front since they're ...



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