Tip & How-To about Ford F-100

Brake Fluid misconceptions

I have come across several misconceptions concerning brake fluids. Unfortunately the brake fluids available to us are the inheritance of a by-gone age and we are stuck with the inferior Glycol-Ethyl based fluids because there is no practical way upgrade all the vehicles in the world to the far superior Silicone based fluids, and the two differnet based fluids are not compatible with each other.
Brake fluids need to comply to several stringent requirements, these have been upgrared over the years and are marked by their DOT ratings, most recently from DOT 3 to DOT 4, and the seldom seen DOT 5.1.
Here the main problem arises. DOT 4 supercedes DOT 3, (the older fluid is not meant to be used on older cars) and if you come across any, it is long past its Sell By Date.
The main difference between Dot 3 and Dot 4 is the boiling points of the fluids (which for obvious reasons have to be as high as possible). DOT 3 has a dry boiling point of 205 deg F. while DOT 4 has a dry boiling point of 230 deg F. With a mere 3.7% water added to the fluids DOT 3 boiling point drops to 140 deg F. and DOT 4 drops to 155 deg. F.
Basically, what it comes down to is that DOT 3 fluids should be phased out and removed from systems as soon as possible, even on older and vintage and veteran vehicles and replaced with DOT 4 fluid.
Strictly speaking, if normal maintenance routines are followed, there should not be any DOT 3 equiped vehicles on the roads anymore.

More about this in a following tip.

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1 Answer

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Best regards!

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