Copyright © 1999 by Oak Okleshen. Used with permission. All Rights Reserved. May not be distributed in any form without prior written permission from the author.

Locally, (not an airhead member…) a gentleman acquaintance called me late in the year (several years ago…) and asked if I would help him get his 1982 R100RT in running order. He stated the machine was not ridden in over 2 years and was in storage in his aircraft hangar. The battery was dead, and the windshield cracked as something had fallen on it. So he requested generic repairs and a full 10,000 mile maintenance schedule to be performed. I wasn’t fond of working on it just then but he insisted and not running at the time, trailered it out for work. I knew the machine well, as it had been in pristine condition prior to his ownership when purchased from another acquaintance locally…

Considering the period of time the machine laid around inactive, one of the first areas I examined was the brake fluid, being as I need to order parts I might as well determine if the brake system was in working order. SURPRISE… Both the front and rear brake were in a TOTAL STATE OF FAILURE. The brake fluid had literally turned into chocolate fudge compound and all the lines were solidly plugged with deteriorated particulate matter. The master cylinders both front and rear were totally damaged, as were the wheel calipers and in short, the ENTIRE BRAKE SYSTEM needed replacement. Parts were relatively cheaper then, and with the repairs and maintenance elsewhere his total costs approached 2500 dollars.

If this incident doesn’t hit home, I should mention that there have been THREE other instances locally where brake fluid flushings were ignored and components had to be replaced at abominable and totally unnecessary costs. After all, brake fluid itself is quite inexpensive by comparison!!

Some not too many years ago, at a large rally, I went around examining brake master cylinder reservoirs (handlebar mounted) on perhaps several hundred machines. MOST exhibited brake fluid that was virtually black and deteriorated. Fortunately, the brake systems were still working, but it was a series of accidents waiting to happen. So what is all wrong about these scenarios, and what is the proper thing to do??????

Before I get into any more details, there are several articles in AIRTECH pages that are highly pertinent and should be reviewed. In the July 1995 issue, there is a FEATURE article WHY YOU SHOULD NOT USE DOT-5 Fluid. This article was composed (and then edited) by a long time pro on the subject (Steve Wall), a friend of mine thus there is no more need to discuss the DOT-5 fluid issue. Of those still curious, please refer to that issue of AIRTECH.

The other article was in the Dec 1995 AIRTECH pages and part of one of my submissions regarding long time storage (over the winter…) and in brief (item #3 of the article) discusses the need for brake fluid change. The main thrust of the discussion was that if the brake fluid was left in the system too long, it will positively wreck the brake system components.

Now let’s continue…

WHY DOES LEAVING BRAKE FLUID IN THE SYSTEM TOO LONG CAUSE DAMAGE?

The answer is quite simple. The DOT-4 and DOT-3 fluids permissible in the BMW hydraulic brake systems are HYGROSCOPIC, which means they have an affinity for moisture. Given enough time, moisture will enter the system and cause corrosion problems and deterioration of the system. ALSO, with AGAIN, the protective additives in the fluid diminish with time and compound the possibility of damage.

BMW/NA has gone through the trouble to have FREE brochures printed and distributed at rallies and dealers etc., for the owners to pick up and read, pertinent to brake fluid maintenance. They didn’t do this to sell brake fluid and related services. They did it to save you problems and have a safe running machine.

FAILURE TO FLUSH THE FLUID AND RENEW IT ON AN ANNUAL BASIS OR AT 10,000 MILES OF USE (whichever comes first) CANNOT BE OVEREMPHASIZED. If you stretch your luck, and even if the fluid LOOKS clean but is over 2 or so years old, corrosion can start in and damage insidiously starts in. The boiling temperature of the fluid gradually lowers and if let go long enough, can in a very surprising way cause a lockup of the brakes while you are in motion. The result?? You may end up going right over the handlebars!! Need I elaborate further??

I should add, that while the AIRHEAD machines do not have ABS, for those who may have the ABS system on their second machine, if the system gets deteriorated with stale fluid, you may wish to add another 1500 or more dollars for new ABS components too!!

WHAT SHOULD I DO TO PREVENT PROBLEMS WITH THE HYDRAULIC BRAKE SYSTEM??

The answer couldn’t be simpler. MERELY FLUSH OUT THE OLD FLUID ONCE A YEAR OR AT 10,000 MILES OF USE, WHICHEVER COMES FIRST. For those machines permitting DOT-3 fluid, it is readily available at just about all the automotive parts and accessories stores. DOT-4 is somewhat more difficult to obtain but now is available at your dealer in newer packaging. The latest information I have is…(Oct 98)

In all instances DOT-4 can be substituted for DOT-3 as it has somewhat IMPROVED characteristics. It is not recommended that DOT-3 be substituted for DOT-4 as the life expectancy may not be as substantial and performance of the fluid not as good. (In emergency it may be permissible if flushed out reasonably soon thereafter and replaced with DOT-4…)

HOW DO I FLUSH OUT THE SYSTEM AND REPLACE THE FLUID??

Normally this takes some expertise and if you believe you are capable, there are some basic rules to follow…

1. DO NOT CONTAMINATE THE BRAKE FLUID SYSTEM WITH ANY SOLVENTS OR CLEANERS AS THIS WILL MOST CERTAINLY RESULT IN DAMAGE TO THE COMPONENTS.
2. Assists used in bleeding the system such as hoses and fittings may be WASHED in WATER but must be perfectly dry before any use.
3. Empty the reservoir using an ear syringe or suction cup of sorts. Fill it with FRESH NEW FLUID of the correct type.
4. At the caliper, attach a short plastic clear hose to the caliper bleed screw so you can SEE what is coming out. Make the hose long enough to drain into a container.
5. KEEPING THE RESERVOIR AMPLY FULL ENOUGH TO AVOID DRAWING AIR INTO THE SYSTEM, loosen the bleed screw and pump the master cylinder, forcing out the old fluid. BEFORE RELEASING THE HANDLE OR LEVER TO REPUMP THE MASTER CYLINDER, LOCK THE BLEED SCREW. This prevents drawing air into the system when you relax the master cylinder for a repump. Now pump the master cylinder up again and then release the bleed screw just as you did the first time. Repeat the entire procedure until the fluid comes out absolutely clean and free of any air bubbles etc… Do so for a second caliper if you have one. When done, make sure the bleed screws are snugged properly and the master cylinder is at its proper fluid level.

WHAT OTHER CONCERNS MAY THERE BE WITH THE HYDRAULIC BRAKE SYSTEM?

Yes, there is another concern that is RARELY discussed. That is the LIFE EXPECTANCY OF THE FLEXIBLE HYDRAULIC HOSES. There seems to be no set figure published, but by my observation I have seen them get quite stiff after 10 to 15 years of use. That certainly is a sign of aging, and may suggest they be replaced certainly by 15 years of use.

Also worthy of mention is the use of AFTERMARKET stainless steel brake lines. These are generally manufactured and meant for use in SEMI-RIGID applications. At the local dealer, machines have come in with these braided lines and the braid was FRACTURED from flexing. This could easily be the precursor of a disaster. I would recommend NOT using aftermarket lines-stay with the STOCK BMW brake components.

Also, if any DAMAGES had occurred to the hydraulic brake system components, components will have to be repaired and/or replaced. This will entail OPENING UP the hydraulic circuits. Upon completion of repairs, the system will likely refuse to accept brake fluid pumping through the master cylinder and the entire system. And if the master cylinder is excessively actuated without fluid pumping through, it can easily be damaged. So what’s the answer…

The device needed is a BRAKE BLEEDER. Buying a good professional unit can cost upwards of $2000.00. But don’t fret, as I have already sent Jan Hofman a tech article with photos on how to build the POOR MAN’S BRAKE BLEEDER for less than 50 dollars and it works just as good as the high priced units. If all goes on schedule, the brake bleeder article should follow this one the next month of publication. If Jan gets enough space perhaps he might put both articles in one AIRMAIL issue.

Thus in finality, the rules are clear…

1. Perform annual brake fluid maintenance or at 10,000 miles, whichever comes first. Use only DOT-3 or DOT-4 fluid-whichever is specified.
2. I would suggest you replace all flexible brake hoses by 15 years of usage. (No published rules on that…)
3. If a system stays closed a brake bleeder shouldn’t be necessary for maintenance. But once opened, it will likely be a necessity.
4. And if you haven’t quite absorbed it yet, DO NOT USE DOT-5 BRAKE FLUID IN THE BMW BRAKE SYSTEMS… (See July 1995 AIRTECH pages.)

Contact Oak by sending two detached first class stamps to:

Oak Okleshen #35
22637 S. Ridgeway
Richton Park, IL 60471

Oak passed away April 4th, 2017