About to change lines and rebuild calipers and master cylinders on my 05 Night Train. Are the seals compatible with DOT 4 since HD recommends DOT 5. It's my understanding they are and the DOT 5 was just a paint saver switch. I also understand that they do not mix so now is a good time to change, being that I'm rebuilding the system. The previous owner never changed the fluid, so the fluid and components (seals) are pushing 12 years old.

Also the red Harley manual has sketchy at best instructions on rebuilding of these components, anyone have a better source?

Thanks

 

H-D switched to DOT 4 some time ago. I changed the 03 883 R and the 2000 Deuce from DOT 5 to 4. Just drained the DOT 5 out by pulling everything out through the bleeder valve with a vacuum pump.

Then I flushed three times with new DOT 4. Worked great. The DOT 4 and 5 in the pump reservoir turned to almost solid snot quickly.

In my area it is cheaper and quicker to get DOT 4. This way I don't have to stock both as the newer bikes are all DOPT 4.

Didn't do anything with the seals in either one. Didn't reference any manual. Just bled and filled.

 

Not true..... DOT 5 (silicone based) is a better brake fluid than DOT 4 (polyethylene glycol based).

It has a higher dry boiling point (500 degrees v 445 degrees), a higher wet boiling point (355 degrees v 310 degrees), because it's silicone based, it has a more stable viscosity over a wider range of temperatures, and it's hydrophobic (won't absorb water). That fact that it won't hurt the paint is just gravy....

The reason that HD went backwards to DOT 4 fluid is because DOT 5 does not play well with ABS systems....

If you are not planning on changing over to an ABS brake system, I'd say you're better off sticking with DOT 5....

Now, if for some reason you just HAVE to use a polyethylene glycol fluid, consider DOT 5.1 (not to be confused w/ DOT 5), it has similar boiling temps as DOT 5..... If you're an aggressive rider, this could be a plus...

I stock DOT 4 for my '12 Limited (has ABS) and stock DOT 5 for my '03 Heritage (no ABS, so no plans to change to DOT 4).......

Just my 2 cents..

 

It's actually worth at least a nickle "hattitude" and it will keep it simple for him regarding fluid requirements. His masters are labeled for Dot 5 ( on his application ) and who knows who might be "topping it off" in the future.

 

I say stay with dot5 as well. On leaky resivoir seal is a nice streak on the tank with dot 4. As stated, HD only changed due to ABS brakes.

 

Thanks everyone

 

I am trying to help a fellow rider bring back a ride that has been off the road for over four years.

I thought I would change the brake fluid while I was at it, but can't find any help through manuals or YouTubes.

Do I 'just do it'

Any suggestions appreciated. Thanks in advance,

Virginia Dan

 

Without ABS, just suck 95% of the fluid out of the master cylinder and refill with fresh fluid.... bleed the brakes (constantly checking to make sure you don't run the master dry) and when you see fresh fluid coming out of the caliper you're done!

If you have ABS, do the same, just make sure you don't activate the system (turn on the key) until you are done bleeding. You will have a small amount of old fluid still in the ABS module. You can ride and activate the ABS a couple times and then re-bleed the system, take it to the dealer to have it flushed (they can activate the ABS while flushing and get a complete flush), or just keep it on a 2 year routine of flushing the fluid and I believe the little bit left in the ABS will get refreshed over time and not be an issue...

Just make sure to match the fluid in the system: DOT5 for DOT5 and DOT4 for DOT4.

This job is much easier, especially as a one man operation, if you use a vacuum or pressure tool to flush/bleed the system... but that convenience does cost a few dollars...

Good luck...

 

3 responses to your second point/ One, as I understand it you cannot leave the DOT 5 in the ABS system because the ABS motors will create air bubbles. From what I have read simply shaking a bottle of DOT 5 will cause it to bubble up and the ABS mimics this same effect, introducing air into the system from within. Second, mixing 4 and 5 will create sludge automatically and it stands to reason even that small amount of 4 left in the ABS system after the bleed would react poorly with the new 5, creating goo. Am I wrong here? Third, DOT 5 is sad to be corrosive to the rubber seals in systems not designed for DOT 5.

I hope I am because I did as you suggested above (on my own, not because of the post) and am now very worried.

 

I'm not sure how you thought anyone was advising the OP to keep DOT 5 fluid in an ABS system, or to mix DOT 5 fluid with DOT 4 fluid...

This is a 3 year old thread, but since you have concerns over my advice, I will try to clarify my recommendations to the OP....

Harley originally switched to DOT 5 (silicone based) brake fluid back in the late 60's or 70's because of its superior performance. It has a higher wet/dry boiling point than DOT 3/4 (glycol based) fluids, it's not hygroscopic so it doesn't mix with water like DOT 3/4 (glycol based) fluids, and it doesn't hurt paint like glycol based fluids..

You are correct, that DOT 5 (silicone based) brake fluid, does not play well with ABS systems due to its tendency to form micro-bubbles when the ABS is activated... That is why HD switched back to DOT 4 (glycol based) brake fluid when they introduced ABS brake systems (2006ish)....

The OP was thinking of changing from his OEM DOT 5 (silicone based) fluid to DOT 4 (glycol based) fluid.... He appeared to think that DOT 5 (silicone based) was inferior to DOT 4 (glycol based) fluid, and was only used because it was a "paint saver"... my intent was to inform him that was an incorrect assumption..

He had DOT 5 (silicone based) from the factory (2005 Night Train), he DID NOT have an ABS brake system... so there is NO NEED to change to DOT 4 (glycol based) fluid, especially because DOT 5 (silicone based) is superior to DOT 4 (glycol based) fluid in it's performance and characteristics... No one was recommending that he leave DOT 5 (silicone based) brake fluid in an ABS brake system... FYI, I am unaware of any vehicle manufacturer that sells any ABS equipped vehicle with DOT 5 (silicone based) brake fluid...

You are correct that it is an accepted practice not to mix DOT 3,4 (Glycol Based) brake fluid with DOT 5 (silicone based) brake fluid.

If you are referencing my recommendation to look at DOT 5.1 brake fluid, DOT 5.1 brake fluid is a high performance glycol based brake fluid, so it is compatible with any other glycol based brake fluids (DOT 3, 4)...... DOT 5.1 brake fluid (glycol based) IS NOT compatible with DOT 5 brake fluid (silicone based)...

Hope that clears up any confusion...