Brake Fluid Flush


Well-Known LVC Member
Feb 1, 2011
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New Jersey
Picked up some SS lines and a some DOT3 synthetic fluid. Not sure how much better the synthetic really is but was just wondering how much fluid I might need? Manual doesnt say. Got a large bottle so thinking it should be enough? Also I should start with the back passenger wheel?
AFAIK, all DOT 3 and DOT 4 are synthetic. It's kind of like the thing with R-134a refrigerant. All of it is synthetic, but some cans advertise "synthetic" even though that is redundant. They are hoping to fool you into thinking theirs is better, when it's the same.
Note that DOT 4 is a little better than DOT3 as it has a higher boiling point. If you are heavy on the brakes, you might consider it. DOT 4 can be used anywhere DOT3 is called for (it meets and exceeds all DOT 3 specs).

One "large" bottle will be more than enough to completely exchange the fluid. I don't think that it really matters which wheel you start with, as long as you do all of them. There will be a small amount in the ABS pump that you miss.
Brake Fluid

DOT 4 is better when new, DOT 3 MAY BE better when old (its wet boiling point drops less than DOT 4). Either is fine for normal use.
Actually, the spec for DOT 4 is a higher wet boiling point than DOT 3 wet (and higher dry to dry). Dry DOT 3 is better than wet DOT 4, but wet DOT 3 is not. There is some point to be made that DOT 4 may get wet sooner than DOT 3. It is required for my 325i, so I just use DOT 4 in everything.
Most recommendations when bleeding at the wheels say to start the bleeding at the wheel farthest from the master cylinder. Thus, with the master cylinder closest to the front left, you would start with the rear right, then the rear left, then the front right and last the front left. There are other recommendations about bleeding of the master cylinder and/or modulator; you can find this info and more on the internet - Google it.
Not really disagreeing, but... In the case of the LS, the two brake lines from the master cylinder run to the front right corner of the hood, where the ABS module is. From there they split out into the four lines. The brake with the longest run from the master cylinder is actually the left rear, not the right.

That said, given that they all run separately from the ABS module, I don't see how it matters any more which is done first. I understand why it mattered before ABS. Then one line would run back to the back brakes and split into two at the rear axle. If you did the closer one first, it might wind up with some air pushed into it when you bled the next one. Design is a bit different now.

All that said, if you want to start with the rear left, then do so. It will work just as well as if you started with any other wheel.
... They are hoping to fool you into thinking theirs is better, when it's the same ...

Right around that same time they came out with "curly fries"
Clever marketing scheme but .... still same fries.

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