I agree with Robert and David. I don't that DOT 3 fluid can't be used with
DOT 4, as long as it's not silicone based. DOT 4 has better wet boiling
point than DOT 3, but if it's fresh and uncontaminated, the performance
should be about the same. In fact, I used to use DOT 3 Ford truck brake
fluid in my E30 M3 because it had a very high dry boiling point, and since I
changed fluid so often, I didn't really care about wet boiling point. The
Ford fluid was about 1/3 the cost of ATE Blau.
Silicone brake fluids, usually rated DOT 5, can cause seals to deteriorate
and leak. Bad. But you were smart enough not to put that in.
So don't sweat it. When you get the chance, suck out the reservoir, replace
with DOT 4, bleed the brakes.
----------------------------------
Bill O'Neill
'95 E36 M3 "kompressor"
'90 E34 535i
Date: Mon, 16 Feb 2004 17:45:21 -0500
From: "Gerry Phillips" <[email protected]>
Subject: [bmw] Brake Fluid oops
Hello All,
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?
Thanks in advance.
Gerry A. Phillips
BMWCCA Peachtree Chapter
89 535i
87 325is
------------------------------
Date: Mon, 16 Feb 2004 18:39:45 -0500
From: Robert Chase <[email protected]>
Subject: Re: [bmw] Brake Fluid oops
Hmmmm,
Dot 4 fluid has a different boiling point and water absorbing
qualities. I think its rather similar to Dot 3 otherwise.
If it were
one of my cars I would be making an appointment with my
mechanic to have
the brake fluid changed. I heard of someone putting the
wrong kind of
fluid on one of my other lists (they put some other kind of
fluid [power
steering, transmission or something otherwise bizzarre] in the master
cylender) and it eventually deteriorated his seals in the brakes.
Eventually it required the replacment and major cleaning of lots of
components in the system. I am a "fluid" nazi with my
Mercedes and even
use the special Mercedes fluid in the radiator to keep from
deteriorating the plastic in the Behr radiator (my radiator
is original
and over 22 years old with no problems at all). German cars
in general
are engineered rather tightly and there is less fudge factor
than in any
other type of vehicles.
I dont think the lower grade of brake fluid will do damage
but I would
not reccomend leaving it in the car for more than the time it
takes you
to make an appointment to have it replaced.
Robert Chase
------------------------------
Date: Mon, 16 Feb 2004 15:52:46 -0800 (PST)
From: David Morrison <[email protected]>
Subject: Re: [bmw] Brake Fluid oops
The main difference is boiling point so basically
you've somewhat lowered the boiling point of the total
fluid in the system. Shouldn't be any problem unless
you are tracking it and doing heavy braking. I would
probably just wait till your annual brake fluid flush
... you do flush it regularly right? The water
absorbed by the system would degrade your performance
more than a little blending of DOT 3/4 if its been
more than 1.5-2 years since a flush. Oh, UNLESS your
DOT 4 fluid was the silicon based type, then the DOT 3
fluid is a different type and I would be flushing it
out right away.
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