Where did my brake fluid go?

[6322]

I hesitate to say this since I have not met Kurt, but I assume he is like most other members and is deeply into middle age. Therefore, it is possible, perhaps even probable, that the fluid was never in the fluid reservoir.

Kinda like fake news?

 

[jagarra]

I used Apple Hydraulics to do my 16mm M/C on my R90, they use a brass sleeve. Used Mark Frappier on my vintage Jaguar M/C because i wanted to try stainless and this particular vendor based on the recommendations from a member who restored a R90/6 sometime back. Price was about the same, Mark was a bit cheaper, I believe is that the finish and quality was better with the stainless.

 

[SCBuckeye]

To me, this original m/c is an engineering nightmare and not worth doing anything to it, rebuilding or sleeving. Just a waste of money that could be applied to a better one - on the handlebar.

 

[20774]

Contrary to popular opinion, I finished the overhaul of the original master cylinder. Nice firm lever like I remember. When it came to bleeding, I tried to use a syringe to push the fluid up from the bottom, but I think you need speed bleeders for that. With the caliper bleeder just cracked, whenever I put pressure on the fluid to push it, it found the path of least resistance and came out around the bleeder threads. So, back to "old school" methods. Before I put the master cylinder on the bike, I pushed the piston a number of times with my thumb with fluid in the reservoir until it spit fluid through the outlet. That might have accounted for a "bench bleed". Mounted back on the bike, I kept pumping the lever and watching the level. Surprising not that much in the way of air bubbles. I even tilted the M/C up over night. It's a very firm level so I'm sure there's no air in the system.

I think all this stems from having to replace the caliper piston earlier this year...found brake fluid on the ground. I bled the brakes at the time but never really got that firm pressure, but it seemed good enough to stop the bike. I think during that bleeding, the seals might have drug across compromised areas in the bore of the M/C resulting in lower lever pressure and also leaking past the rear seal. I could seem some rust spots at the very rear of the bore. But I used a socket with sandpaper wrapped around it chucked up in my drill...took me a bit to get the hang of it. Bore looks nice.

First ride was good...brakes feel good.

Thanks to Brook and his blogs...certainly helps a lot when it's 10 years between M/C overhauls!!

 

[m_stock10506]

.....When it came to bleeding, I tried to use a syringe to push the fluid up from the bottom, but I think you need speed bleeders for that. With the caliper bleeder just cracked, whenever I put pressure on the fluid to push it, it found the path of least resistance and came out around the bleeder threads. So, back to "old school" methods. .............

First ride was good...brakes feel good.

Thanks to Brook and his blogs...certainly helps a lot when it's 10 years between M/C overhauls!!

Speed bleeders have a check valve to prevent brake fluid from moving in the reverse direction, back to the MC. So, if you have speed bleeders on the caliper you would have to swap to standard bleeders to push fluid up from the caliper. Sounds like you might not have opened the caliper bleeder enough. If this was a front circuit, I've never had an issue bleeding from the MC down to the caliper. Glad you got it worked out.

 

[20774]

Speed bleeders have a check valve to prevent brake fluid from moving in the reverse direction, back to the MC. So, if you have speed bleeders on the caliper you would have to swap to standard bleeders to push fluid up from the caliper. Sounds like you might not have opened the caliper bleeder enough. If this was a front circuit, I've never had an issue bleeding from the MC down to the caliper. Glad you got it worked out.

Thanks for the heads up on speed bleeders...that makes more sense. I'm not sure opening the stock bleeder more would have helped...it would just have leaked faster! At first, I had it open a reasonable amount but had the leaks...I closed it a bit more, still leaked but slower. Of course, closing it more would have defeated the whole purpose.

I considered getting a MityVac system from Harbor freight...I spent as much on a syringe, rubber tubing, hose clamps, etc.! I was looking for a way to fill the system quicker and then get on with regular bleeding. In the end, there's really not that much fluid in the system.

Brakes sure felt good!

 

[m_stock10506]

I had a problem flushing my brake fluid one time - '84 R100 - where one side of the front would not bleed any fluid. I replaced the small section of brake hose there but the problem ended up being a clogged bleed valve.

 

[lkchris]

Really cold weather can play havoc with old master cylinders ...