Had a knock down drag out with the dealer today cause the gasket was leaking on the rear master cylinder and the damn DOT4 is causing the paint to flake off the resevoir. Service writer told me it was impossible because the "tank" (reservoir) is plastic. Damn near had to shove his head to the ground to make him look at it. They replaced the cover and gasket and told me they would order a tank if the paint (said as he rolled his eyes) continued to peal off.

Does anyone know when (and if) the rear master cylinder resevoir was changed to plastic on the touring bikes?

 

Rear master cylinder COVER was changed to plastic with the 2010 models.

 

Should use dot 5 fluid because it won't harm paint. Cost more for the silicone based fluid, but well worth it, plus the boiling point is a lot higher and it also won't go bad sitting over the winter as the dot 3 and 4 and 5.1 will.

 

That is very in incomplete advice and dangerous if followed without truly understanding all the issues.

Failed to mention that the 2 types of fluids are totally incompatible and the risk of serious damage to seals in the system is very real!

If you want to follow this route, please do very thorough research first!

 

Yes... it is good advice to research the different types of fluids, and true the dot 5 is
NOT compatible with the other types. If you're going to change from one type to the other, then you need to flush the entire system, (front or rear) depending on which you're working on. I have only seen instances on bikes where dot 5 are used, but maybe there are some that do call for the dot 3 or 4. The dot3, 4 and 5.1 are glycol based and will eat paint like a bull dog eats hamburger, while the dot5 is silicone based and does not ruin your paint if some gets on it. Always research any changes you would make to your brakes as this is an area you don't really want to fail. If you do not thoroughly understand the differences and reccomendations for your bike, then consult your Harley dealer. Check your manual too as it probably will tell you the type of fluid for your bike and all the instructions for flushing the system and proper bleeding, etc, etc... and so forth. Good advice from sgdiesel though... never make changes to stuff you're not familiar with until you check it all out very thoroughly. OK... I do believe it's awfully close to beer time, so gotta go. Good luck bro. Hope this helps ya out some and by all means do it right and ride safe. By the way when flushing a brake system... never use any kind of solvents as they can and will cause seals to swell and fail. Flush a system only with the type of fluid that you will be using. Follow closely the instructions for your bike. This is not rocket science, but you need to thoroughly understand it all before you go ahead with any changes.

 

It appears to be a very common problem on front and rear master cylinders on newer Touring bikes. My 2010 had the plastic cover as Dawg alluded to but the gasket was changed sometime later. You could no longer buy just the gasket or cover. You had to buy the upgrade kit. This only applies to the stock black cover. I don't know if the same applies to the chrome. Many whos "front" master cylinder leaks (its more of a weep thats not always noticed initially until you find that the wind has blown the weeping fluid back on your beautiful tank and you one day notice spots in the paint clear coat or worse, that you cannot remove.) The biggest issue to getting the leaks to stop is to follow the new lower torque specs to the letter. It barely feels tight....and completely drying the lip of the master cylinder resevoir before installing the new gasket and cover. I now remove, dry the lip and re torque the cover as general maintenance during oil changes. I started doing this after going through 3 covers and gaskets, and two upgrade kits, (one front and one rear) and after realizing that the small pock marks in my paint, was due to a weeping front master cylinder gasket and the same thing you describe happened to my rear master cylinder resevoir...powder coat on the resevoir started turning chaulky white and peeled. .

 

One other thing I was just thinking about... is if your bike has an ABS system (anti lock brake system), then you would have to use type dot 3 or 4. The dot4 would be the better of the two. Dot5 is not compatible with anti lock brakes in any type of a vehichle. It should say in the cap on your resevoir the type for your bike. It will definitely say in your manual. I ride an old 90 heritage that I built from scratch, so I do not know what bikes use anti lock brakes, but I know some of the later models do. If it is ABS then you have to use type 3,4 0r 5.1 which are all compatible due to being all glycol based. The main difference is in the boiling point and you should use the highest boiling point and dot3 is the lowest of them all. Check with the dealer... I know the older bikes almost all use the dot5, unless they have been changed for some reason. Well, time to pop open another brew... before I forget anymore stuff. I think beer makes you think better. I know with every one I have... I think that blonde shootin pool over there looks better.