2007-01-30 13:58:43 · 6 answers · asked by ricky p 2 in Cars & Transportation ➔ Maintenance & Repairs
A short answer is that Dot 4 has a higher 'boiling point'. As breaking increases the heat raises the temperature of the fluid, making it 'breakdown'.
2007-01-30 14:04:51 · answer #1 · answered by drysac 4 · 0⤊ 0⤋
Well, brake pads cause friction, and friction causes heat. Now I could be a smart as* and tell you the difference between dot 4 and dot 3 is one dot. But the real answer is the boiling point of the fluid.
DOT #3 is 401 deg. F., DOT #4 is 446 deg. F., and DOT #5 is
500 deg. F. Over time, though, the heat generated from braking causes the chemical composition of the brake fluid to change. Gasses are boiled out of the brake fluid and since these gasses are more compressible than the brake fluid they came from, you will notice a soft or spongy brake pedal feel.
There is even a dot 5.1, but you probably won't find it (or dot 5 for that matter) at the parts store.
If dot 5 has a higher boiling point, why don't you see it? Water.
DOT #3 and DOT #4 brake fluids are made from Polyalkylene Glycol Ether which, by nature, has a very strong attraction to water (brake fluid is hygroscopic). Water contaminating brake fluid makes its boiling point drop which causes bubbles to form in the brake fluid (imagine sprinkling water into a frying pan full of hot oil). Bubbles and water are more compressible than brake fluid which makes it more difficult for the master cylinder to compress the brake fluid and in turn, compress the calipers and brake drums. A sign of this may be a low, soft, or spongy brake pedal feel (caused by the the contaminating bubbles and water compressing before the brake fluid does).
DOT #5 brake fluid, on the other hand, is formulated from silicone. While silicone is not hygroscopic and has a higher boiling point than DOT#3 and DOT #4 brake fluid, any water that gets into the brake system will sink to the lowest point of that system (water being heavier than silicone) and may potentially find its way to the calipers, boil at 212 degrees Fahrenheit and cause a vapor lock which could cause brake failure. Additionally, DOT #5 brake fluid, being a synthetic, is much more expensive than DOT #3 and DOT #4 fluids, hence Tire Kingdom uses DOT #5 brake fluid only at the request of the customer.
Most major vehicle manufacturers recommend having your brake fluid replaced about every 2 years (more often in severe driving conditions). Draining and replacing your brake fluid helps to remove contaminants (such as water and rust) and to lubricate the metal and rubber parts of your brake system (like the master cylinder, brake lines and seals, valves, wheel cylinders and caliper pistons) which may help them last longer.
Too much information? Probably.
2007-01-30 22:10:53 · answer #2 · answered by oklatom 7 · 2⤊ 0⤋
dot 4 withstands higher temps. you can use dot 4 for dot 3 but not the other way around.
2007-01-30 22:07:31 · answer #3 · answered by HONDALUVA 2 · 0⤊ 0⤋
bolling point, the material used to make it, dont mix dot 3 and dot 4. you will destroy brake parts and wont be cheap to fix
2007-01-30 22:05:55 · answer #4 · answered by dusty k 2 · 0⤊ 1⤋
What's the difference between Pepsi and Coke? Difference between type F or dextron auto trans fluid?
Be safe. Use what manufacturer specifies.
2007-01-30 22:08:22 · answer #5 · answered by ButwhatdoIno? 6 · 0⤊ 2⤋
the boiling point.
2007-01-30 22:01:45 · answer #6 · answered by rasco 3 · 2⤊ 0⤋