Changing the brake fluid

The cap has not been off of my mastercylinder in at least 12 years so I think a total fluid change is in order. What is the best way to do this on my Seca 750 and what type of fluid would you recommend (Dot3 - Dot4 - Dot5 - Dot Dot Dot.

Also, I currently have no leaks whatsoever so am I running the risk of creating problems by a total flushing?


thanks

 

I had to completely rebuild the MC and the caliper on my 650 due to it sitting in my father's garage for over 10 years. Honestly the best thing to do is completely disassemble the system (drain it first silly). Then inspect everything (MC, hoses, Caliper). If there were no signs of water absorption, then replace the copper seals on the hoses. Back fill the brake system (using a pump, fill the caliper until fluid shows in the reservoir). Top off the reservoir and bleed.

I actually decided that my brake lines were too dry rotted to put back onto the bike again. I opted to get a 40" SS hose and banjo fittings from Jegs. After the work was completed, and the new hose was installed, I just couldn't tell you exactly how much better the braking was on my 650.

Before you go and swap brake fluids, you have to ask yourself if going to the DOT5 is worth the costs. I have used nothing but DOT4 in all of my bikes. It's not overly expensive. But then again, I only flush out my brake systems once a year.

But to quick answer your question.... If you do go with a DOT5 fluid, make sure you get all the old fluid out first.


Just my $0.02,

 

One thing I can say after learning the hard way is to be careful with those cover screws. Breaking them can create a lot of problems, and an EZ-out sure wasn't the way to go for me.

Take the time to search for "master cylinder screws" or "stuck fasteners". I wish I had...

On your other questions, I'm sure someone with greater experience will jump in.

 

Thanks for the feedback.

My lines are in great shape no cracking at all. My brakes work pretty well but I know it's time to change the fluids. I picked up a fresh bottle of Dot 3 the other day would I see any benefit if I were to go with the Dot4?

 

DoT3/4 is fine, going to DoT5 will require a complete teardown to get it completely clean. If you really want to trust it, just flush it THOROUGHLY with new fluid and bleed. If not, then tear everything down and rebuild. In between those extremes, replace the lines and brake pads and flush/bleed the system. If there's no signs of water incursion then flush and bleed. The master cylinder on my '81 was full of brake fluid JELLY (and the PO was riding it!!!) so I vacuumed it out with a shop vac rather than flush crap through the system.

 

You say you have no leaks. Does the brake function?
The brake fluid in my MC actually turned to dust. It took time but I did flush the MC, lines, fittings, and caliper. Works like a champ again. I know people will probably shreik at me doing this and for not replacing everything but I wanted to do it old school and make sure everything worked mechanically before I spent a lot of money. Once I do the valve clearance check and it runs totally to my liking I'll go back and start upgrades. Oh yeah I did upgrade the MC screws to allen type from chacal because I stripped one of them and had to easy-out it. :lol:

 

Guys I should have been more specific in my post. My bike still has less than 10,000 miles on it and is in near perfect condition. The brakes work well I am just thinking a total fluid change is way over due.

Would siphoning the fluid out of the mastercylinder refilling with new fluid then bleeding until I see clean fluid be the best way to go?

 

that will work just fine, if the fluid has not turned to jelly yet. don't forget the anti-dive cylinders if you have them.

The guys are right though - brake fluid deteriorates after a while, regardless of what the mileage is. When was the last time it's been changed?

It has been changed, right? 8O

 

I wouldn't siphon it out.
Get a Syringe and just use it to drain the Master.



After the Master is Drained ... shoot it with Brake Parts Cleaner.
Syringe-out the cleaner
Q-Tip the window clean
Kleenex the MC dry.

Fill it up with some fresh, clean Brake Fluid.
Bleed the system until what come out is as clean as what you put in and YOU have flushed and cleaned the Brakes.

 

I doubt it :cry:

 

Rick, that a great idea. We have a couple of those "snot suckers" left ovre from when the kids were young

 

I had the same situation with my '81, worked fine but hadn't been touched. Opened it up to do a preventive flush since I had just taken the bike over, and found jelly. Cleaned it out, flushed, pulled caliper off its mounts, cleaned and lubed that whole assembly, put it all back together with clean fluid and it's fine. I too stripped one of the MC screws and used a Craftsman extractor on it. I plan to replace the lines during winter layover, though. Oh, and one more thing: I replaced the rubber MC cover gasket/diaphragm as it was permanently "squished" and crispy around the edges.

 

Even though your brakes may work fine, do yourself a favor as the others above have suggested and clean/inspect all brake system components. You will probably be surprised at the amount of goo you'll find in there which you'll want to clean out - I certainly was - it was actually stunning. It's relatively easy to do. After all, you want to make sure that your brakes are top-notch, without question.

 

There was a thread a few weeks (months even?) ago that had a link to some great, very in-depth data about the differences between DOT 3,4,5 fluid.

It basically boiled (ha ha..) down to the fact that 3 and 4 are basically interchangeable, although 4 is the 'better' of the two, with a higher boiling point. They are both organic.

5 has a different chemical makeup that prevents it from absorbing water.

Because 5 can't absorb water you MUST change it MUCH MUCH more often or you will have catastrophic brake failure.

Because 3 and 4 absorb water they will evenly mix the water throughout the system, preventing a build up. 5 allows the water to collect (and IIRC, it is heaver than brake fluid so it settles in the caliper.), where it is much more likely to boil and turn to compressible steam. Resulting in NO brakes when you need them most (i.e. after holding them long and hard).

The water can also cause corrosion.

There is a new 5.1 what is the best of 3/4 and 5.