[bmw] RE: DOT 3 brake fluid

["ONeill, William" <William_ONeill@xxxxxxxxxxxxxxxxxx>]

 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" <gphill03@domain.elided>
> 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 <beostar@domain.elided>
> 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 <davidm3286@domain.elided>
> 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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