[bmw] RE: Brake Fluid oops

["Dennis Liu" <BigHeadDennis@xxxxxxxxxxxxx>]

Gerry Phillips wrote:

>I messed up and I need to know how badly.  I checked my brake fluid
reservoir on my '89 535i this past weekend and it was low.   I've topped
off my brake fluid in the past and I know my car calls for Dot 4, but for
some reason I picked up Dot 3 and topped it off with that.  I guess I was
too busy thinking about spending a nice Valentine's evening with my
fiancee.  I realized it after I had already done it.  My questions are:
Will Dot 3 hurt anything?  Should I have the system drained and refilled?
And what are the differences between Dot 3 and Dot 4?
____________

Don't worry about it.  As others have noted, formulations between DOT 3 and
DOT 4 are the same, except boiling points (wet and dry) are different.  DOT
3 is used on a lot of vehicles, as it is somewhat cheaper.

The concern is if one used DOT ***5***, which is a silicone-based fluid and
is incompatible.  THAT can cause some serious problems.  Note that DOT 5.1
IS not silicone, and is actually compatible.  Nice and easily
understandable, huh?

If you flush your system once a year, I'd wait until the next annual flush.
The worst adverse effect, theoretically, is that you'll have a greater
chance of boiling the fluid with hard use, but unless you're taking the car
to the track or riding the brakes while coming down Mt. Washington, I
wouldn't worry too much.

vty,

--Dennis












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