Re:Synthetic Brake Fluid - - Excellence in Motion
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post #1 of 20 (permalink) Old Mar 5th, 2008, 11:07 pm Thread Starter
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Re:Synthetic Brake Fluid

I need a little advice on this. My "02" K12RS has turned over 12000 miles and I wont be able to take it in for it's "check up" and at the same time I've been having some issues with the brake failure warning lights always coming on. The 1st time it turned out to be excessively warn rear brake pads and after having them replaced the problem went away for about a year, and now ever since about last summer the problem has been intermittent but goes away after the bike is thoroughly warmed up and the brakes have been used a substantial amount, and through all of this the brakes have never been bled and the fluid has never been replaced. I just got some DOT 4 synthetic brake fluid and I plan on removing as much of the old brake fluid from the resevoir's as possible then add back to the proper level the new brake fluid. What I need to know is will the synthetic brake fluid conflict with the old non synthetic brake fluid that is in the bikes system that I can't remove? According to the info. on the bottle (Prestone brake fluid) it says it will not, but as our bikes are a bit unique I don't want to take any chances. Thanks for your helps with this.:-)
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post #2 of 20 (permalink) Old Mar 6th, 2008, 4:37 am
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Synthetic has a lot of advantages, most of all it absorbs water less and doesn't damage paintwork.

However, only DOT4 is fully compatible with the braking parts (rubbers etc), unless this has changed on the very latest bikes. So you have to be careful what you read on the bottle. Whilst a manufacturer of fluid may claim compatibility with DOT4, they aren't saying their synthetic is compatible with your rubber seals, hoses and pistons are they? A bike built in 2002 could have braking parts specified and designed in the 1990's when synthetic fluids weren't available.

There are many riders including myself using DOT4 who don't have ABS problems. First flush through with new DOT4 then make sure the reservoirs are topped up. Yes, as pads wear the reservoir levels will drop and what you describe sounds a better indicator of worn brake pads, than the new hi-tech system now being fitted which has caused a lot of errors and problems. But also check you have no leaks which are dropping fluid levels.

Your bike whilst low mileage, is a few years old and its DOT4 fluid will may have absorbed moisture. If you still get problems with ABS warning lights, then you move to checking sensors and the hydro unit. I think most here would flush a system every couple of years, It's got more to do with time spent in the system, than miles on the odo.

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post #3 of 20 (permalink) Old Mar 6th, 2008, 5:59 am
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Please also note that the use of synthetic brake fluid can cause "pad knock off" when used in some applications. This can result in more brake lever travel than regular brake fluid.

I haven't had feedback from anyone who has used synthetic fluid in BMW calipers so perhaps someone on this forum may know?
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post #4 of 20 (permalink) Old Mar 6th, 2008, 10:05 am Thread Starter
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Re:Synthetic Brake Fluid

Thanks for you helpful responses. If what is printed on the bottle is to be believed it says. "Good for ALL DOT 3 & 4 brake systems, ABS, DISC & DRUM Brake Systems." It also says it is a DOT 4 brake fluid not DOT 3. I can't bleed my brake system and I can not find anybody in my immediate area (Port St. Lucie FL) who will even touch my brakes because of the ABS system and even the guy who replace my rear brake pads last year would only just do that part only and would not try and bleed them, so I'm left with removing just what is in the reservoir's only and then toping them back off with the new brake fluid. Thanks again for you help with this.:-)
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post #5 of 20 (permalink) Old Mar 6th, 2008, 2:38 pm
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the lite coming on is in most cases low master cyl (rear)

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post #6 of 20 (permalink) Old Mar 6th, 2008, 4:25 pm
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I do not use synthetic brake fluid.

After ruling out the battery, the levels in all 3 reservoirs and the sensor gaps, I troubleshot mine using a GS-911. The bike stores the failure. Mine read something like "rear pressure too high" My problem stopped occurring after a brake bleed and exersize of the rear caliper.

If I were to have to troubleshoot again and didn't have a GS-911 I would look at the frequency of the warning lights (general error and abs error). It may be as simple as a bad tail light bulb. Here is a fine read on the subject outlining what the frequencies means:

I'm your lights are flashing?

BTW, my issues went away after changing the fluid using a process similar to this one:
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post #7 of 20 (permalink) Old Mar 6th, 2008, 4:49 pm
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I would stick to the non syn. brake fluid......syn. brkake fluid with silicone will not absorb water but instead the water and the fluid will not mix and you will get small drops of water in your system that can lead to corrosion to your brake lines....and pockets of boiling water in your system......not sure ..but...think when you bleed brakes with syn fluid you have to use the vacuum method of bleeding......better to stik to true and tested fluid.....But haven seen this stuff sense the early 90s....but maybe you have somthing new?....
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post #8 of 20 (permalink) Old Mar 6th, 2008, 6:34 pm
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Brake luid

Well I just asked the boys at my shop about having them change out the brake fluid in my 2002 KRS and they said it's a good idea, as they pointed to a customer that just had an ABS unit replaced. He bought a used RS and the previous owner never changed the fluid and he got stuck with the bad unit. They are over $2000.00 to replace unless you locate a used one. My personal experience with adding synthetic to what's already there was bad. I did what you want to do on my old KLT and ended up with a brake fault light constantly reappearing. When it was all done with, I had a bad valve in the ABS unit. Fortunately I crashed the KLT and it was written off as a complete loss so someone else inherited the problem. If I were going to put synthetic fluid in I would remove all the original fluid and have synthetic throughout the whole system. Did I say "fortunately I crashed"? :wtf

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post #9 of 20 (permalink) Old Mar 6th, 2008, 7:40 pm Thread Starter
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Re:Synthetic Brake Fluid

My brake failure light and the triangle with the exclamation point in it both alternately flash, and when I look I can see that the fluid is just a hair's width below the "MIN" line and after the bike is good and warmed up and I've done lots of braking I can do a restart and the lights will more then likely stay out unless I do some violent maneuvers that shake the reservoir all up then the lights come back on and I have to do a restart again to make them go out. I have no idea (or tools) to do a complete bleed of my brake lines and if the local motorcycle shops wont touch it I'm not about to stick my fingers into it! I know my bike has some years on it ("02" that I bought in Aug. of "01") but it doesn't have much more then 12000 miles on it and the fluid looks pretty clean for the most part. The reason I want to put the Synthetic brake fluid into it is for the very reason that it's not as hydroscopic as "normal" brake fluid and living here in humid Florida that just makes sense to me. This is Prestone brake fluid and as far as I know it's got a good rep. so I guess I'm going to go with it and I'm pretty sure if I just filled it up to the proper level the lights would stay out but as it's never been changed out in any way since I got the bike in Aug. of "01" I thought I should at least do something to "freshen" it up a bit.:-)
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post #10 of 20 (permalink) Old Mar 7th, 2008, 9:22 am
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OK. Sounds like you know the solution. I'm sure there is someone with more knowledge on the subject but this is how I understand it from google:

DOT 3,4 and 5.1 appear to be backward compatible, synthetic or not, exluding a requirement for mineral oil. These all absorb moisture (hygroscopic) but are OK in our systems. You gain a higher boiling point with each version.

5 is NO GO. It is silicon based and any moisture will not be absorbed and will remain as droplets. It has been said that DOT 5 will damage our seals but not the paint.
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