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pj4

brake fluid

7 posts in this topic

can a person mix dot 4 with dot 3 fluid? i understand dot 4 has a higher boiling point, also not to put dot 3 in a unit with dot 4.

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I guess that you answered your own question. If you can't mix dot 4 with dot 3, then you can't mix dot 3 with dot 4 - ins't that the same thing?

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There would be no benefit to add DOT 4 into a Dot 3 system. The boiling point would remain the same as if you had never added DOT 4, unless the complete system was flushed so that 100% of the DOT 3 was removed. If any DOT 3 remains in the system than the boiling point will always be DOT 3 no matter what fluid you add.

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DOT 3, DOT 4 and DOT 5.1 are all compatable to mix.

Many people are not aware of the difference between 5.0 and 5.1: 5.0 is Silicone based, and CANNOT BE MIXED with anything else. 5.1 is a super high spec using the same type base fluids as 3 and 4. Hence, 5.1 is compatable to mix with 3 and 4 without causing damage. If you mix 5.0 with anything else you will attack all the rubber and synthetic rubber components and you will have no brakes!

When comparing new fluids, there is no benefit to adding a higher number / spec fluid - that is mixing two different ones.

However, if you have DOT 3 that is 2 years old and the boiling point has dropped by a lot, sometimes over 100 deg, topping off with 1/2 pint or more of anything else will improve the overall quality of the fluid.

ALL of today's cars should have the brake fluid flushed every 2 years. All Brake fluid will absorb water and drop boiling point, and needs to be flushed. It is not hard to do - first use a turkey baster or something similar to remove as much as possible from the reservoir (of course, you'll never use it for your turkey again). Fill the reservoir with new fluid. Then do a complete brake bleeding procedure on all 4 corners starting with the furthest away - usually right rear, left rear, right front, then left front. Bleed or purge at each wheel until you get fresh new fluid. Of course check and keep the reservoir full.

All of today's cars with antiskid, antilock and traction control systems recommend this as a preventative maintenance procedure!

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3 years/36,000 miles is a common service interval for brake fluid. If its brown and nasty its way overdue!

Brake flushes are one of the few "maintenance services" that IMO are very bennificial!!

All of the Linn Companies service locations provide this service.

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thanks a bunch for all the info.as ive said before, got to love this web site for the vast amount of information .

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