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Discussion Starter #1
I went to the auto part store for some dot 4 fluid all they had was valvaline synthetic dot 3&4 all in one fluid. can I use this to flush my brakes
 

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Yes, the 3/4 Valvoline is just fine. The 3/4 dot means that the fluid meets or exceeds the brake system requirements, for dot 3 and 4.. BMW says you can use Castrol fluid. I suspect Castrol is bottled for BMW. I've used Valvoline 3/4 with no problems.
 

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Danger Will Robinson: You cannot mix regular ether based brake fluid and silicone fluid, period.

If the bottle says that is compatible with regular fluid you should be OK - but just beware if it's silicone - from my understanding all "synthetic" brake fluid IS silicone based.

You need to completely purge the old system first before installing silicone, and it's very difficult to get it all out. You will also probably have issues with seals and o-rings failing which if involved with the ABS system can get obscenely expensive to repair - and I mean to the tune of several thousand dollars. :eek:

Generally speaking you should only use silicone for replacement if you know it came from the factory that way. Almost all of the newer cars have silicone installed, the advantages are many: longer service life, higher boiling point and it's not hygroscopic. These systems were designed from the get go for synthetic silicone - and are highly engineered.
 

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Just a smart a** question, but, silicone DOT 5 aside, aren't all DOT 3 & 4 brake fluids "synthetic" in the sense that they're not "natural" oil products? Asked another way, what's the difference between synthetic DOT 4 and "regular" DOT 4 brake fluid?

Just wondering.....

Jeff D
 

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Roamrider said:
Just a smart a** question, but, silicone DOT 5 aside, aren't all DOT 3 & 4 brake fluids "synthetic" in the sense that they're not "natural" oil products? Asked another way, what's the difference between synthetic DOT 4 and "regular" DOT 4 brake fluid?

Just wondering.....

Jeff D
Yep, I guess you could call all of them synthetic since each manufacture has their own "formula". The end result is they all have to meet a specification.

There is - however - a huge difference between ether based and silicone based.

Personally, I use brake fluid distilled from endangered Western Pacific grey whale oil - it's mo' bettah and natural. :D
 

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So it sounds like we're all in agreement here. Dot 3, Dot 4, and Dot 3 and 4 are not silicone base.

And by the way Ron, the fluid I use is distilled from the tear ducts of the Sierra spotted yellow-legged frog.
 

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seahabit said:
So it sounds like we're all in agreement here. Dot 3, Dot 4, and Dot 3 and 4 are not silicone base.

And by the way Ron, the fluid I use is distilled from the tear ducts of the Sierra spotted yellow-legged frog.
But wait - there's MORE! ;)

Of course there's 5 - which is silicone based - and then 5.1 - which is ETHER based and 4X as expensive as 3 or 4. :eek:

I run into the same problem every time I buy a tube of toothpaste. All I want is minty fresh breath.

Who make all this up, anyway? It's enough to drive a guy nucking futs. :crazy: :D
 

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Discussion Starter #8
well my lt is a 2000 with 13k miles. I think that the brake fluid is probably original from the factory the front caliper still have the weird cap in place were a regular bleeder valve goes. and what am planning to do is go thru an entire bottle of brake fluid to make sure all the ol d fluid is out
 

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If the brake fluid really is the original factory fluid, flush, flush, flush at each caliper. Once they come out clean, flush the ABS unit. The BMW Repair Manual says the ABS unit doesn't need to be flushed unless the system is drained or opened. Even so, a little of the coffee-colored fluid will remain right at the bleed nipples. There are springs and ball check valves under the bleed nipples on the ABS unit. Might as well get all the old fluid out while you're at it. The front nipple is for the front circuit. The rear nipple is for the rear circuit.

In case you haven't seen the thread, put a razor blade, quarter, etc. in the reservoir. There is a small hole in the middle of the reservoir that will squirt brake fluid onto the upper wind deflectors and down onto the paint without something covering it up. I suggest a quarter because you might forget to remove the blade. In this economy, nobody would leave a quarter laying around! :D
 
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