Brake Fluid Reservoir Empty - Again? - K-Bikes.com - Excellence in Motion
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post #1 of 19 (permalink) Old Jan 5th, 2006, 5:31 pm Thread Starter
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Brake Fluid Reservoir Empty - Again?

Late in October, I posted a question about filling the rear brake fluid reservoir - but didn't know why it was empty, since the ABS system had just been serviced at the dealer.

Adding Brake Fluid

After filling this same reservoir to the "full" mark, I made arrangments for the dealer that did the ABS servicing to pressure check the whole system, since they said they were sure they'd filled it up. I parked the RS for quite a while before I had time to take it in, and between filling it up, having it pressure checked - they told me it passed, and now, I've put only a few hundred miles on the bike.

Now the same section of the reservoir is nearly empty again. but so far, I don't see any signs of fluid leaking from anything visible.

Does anyone have a suggestion on where to look?

I'm starting to wonder if I'm real or a troll I don't see how one bike can have so many failures. Every time I think everything's been taken care of and I can sell it with a clear conscience, I find something else. Now it's a mysteriously empty brake fluid reservoir - for the second time in a few hundred miles, and a leaking front shock.

If it weren't for my VFR always being set to go when I'm ready to ride, I'd think I didn't take care of my toys, but really, I'm not that hard on things! :o

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post #2 of 19 (permalink) Old Jan 5th, 2006, 9:09 pm
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That was the front brake wheel circuit,correct?
How about starting with removing the seat and the left-rear body work and check the hoses from the reservoir to the servo pump, the fittings at the pump and spray everything with brake cleaner that possibly looks wet.
Check those reservoir vent hoses and be sure the ends of the hoses are cut at a 45 angle. Make sure the reservoir itself is not cracked.
Is the reservoir oily and dirty? It should be nice and dry.
If you can't find anything and all appears to be clean and dry. Refill the reservoir and start parking that bike on paper to look for leaks.

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post #3 of 19 (permalink) Old Jan 5th, 2006, 10:27 pm Thread Starter
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Quote:
Originally Posted by brucecha
That was the front brake wheel circuit,correct?

Bruce C
Yes, it was and is again. I've got all the plastic off, including the back seat section on the reservoir side, and the reservoir is fairly clean, and the hoses leading from it show no signs of leaks. I'll be able to get more into it on Saturday.

I haven't been able to find any pictures or drawings that show anything about the ABS pump, so I don't know where things connect from the reservoir to the pump. I really hope something's obvious, although if it is, my dealer should have found it.

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post #4 of 19 (permalink) Old Jan 6th, 2006, 6:07 am
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kinda sucks, but it's all I got ...

Quote:
Originally Posted by OCRSRider
.......I haven't been able to find any pictures or drawings that show anything about the ABS pump ......
This link isn't much help, but maybe better than nothing.
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post #5 of 19 (permalink) Old Jan 6th, 2006, 7:50 am
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Originally Posted by OCRSRider
Yes, it was and is again. I've got all the plastic off, including the back seat section on the reservoir side, and the reservoir is fairly clean, and the hoses leading from it show no signs of leaks. I'll be able to get more into it on Saturday.

I haven't been able to find any pictures or drawings that show anything about the ABS pump, so I don't know where things connect from the reservoir to the pump. I really hope something's obvious, although if it is, my dealer should have found it.
The pump is on the left side, behind the rear-quarter plastic, directly behind the accessory electric port.
The reservoir should be spotless, not like it was in those first pictures you posted.
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post #6 of 19 (permalink) Old Jan 8th, 2006, 12:47 am Thread Starter
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I'm at a loss...

Every piece of plastic and the gas tank were off today, and a friend helped me wash and check every inch of the bike. If brake fluid leaked out, it didn't leave any spots, marks, or stains.

I'm at a loss as to where the fluid went, either this time, or the last. I filled the reservoir up again. Now that everything is spotless, if anything leaks following today it should show up pretty easily.

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post #7 of 19 (permalink) Old Jan 8th, 2006, 6:05 am
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Fluid and hydraulic problems like this can be very frustrating. Your braking system has moving seals, so static testing may not reveal all. I would put first trust in a pressure test if competently done, tricky though, because seals might get better according to the direction of pressure.

Fluid loss can be in 2 ways - the standing head of the reservoir and fairly large hole somewhere, or fluid loss from a very small hole or seal on the high pressure side somewhere, which would only occur when braking. On the latter, if you applied the brake on the stand for several minutes with motor running, I'd expect the pressure to sag

You need to get more into the sytem, but pressure tests might need to be done in 2 directions - at the filler cap and at the bleed nipples with a sealed reservoir cap. One other possibility is an air lock in the system between the reservoir and first lump of hydraulics. When bled the system could work perfectly as there's not much fluid drop needed in the reservoir for braking. With positive pressure testing, there is a chance of trapped air being introduced afterwards and the system should be fully bled through. If you are replacing a reservoir quantity of fluid on a regular basis then any airlock would have moved through.

I haven't delved into these ABS systems, but check if there's a possibility of a seal leak and fluid accumulating in a void somewhere. Similar to what might happen in an enclosed clutch housing.

I don't know what BMW's pressure testing procedure is. Is it a test of braking fluid pressure or designed to detect leaks? It might just be a guage on a nipple with brake applied. That wouldn't find a reservoir leak. If a low test pressure e.g about 1/2 psi from a cycle pump and a water guage manometer were left on a sealed reservoir cap for 1/2 hour I'd expect no negligible pressure drop if there are no leaks.

One thing for sure, we don't get diminishing fluid levels in our brake reservoirs - so you are right to look at where it's going. However, you could consider the following:

Fill up the reservoir then date and measure the level before and after each ride. By looking at your log you can work out if any fluid loss is greater when the bike is standing or ridden. That could eliminate the reservoir lines and you'd be looking more for leaks around the working parts of the system. Do the same thing with the motor running on the stand, aggressively applying brakes for long and short periods. The only way you may find a leak with the clean paper method is to excercise the system. Leaks under gravity alone will be very small and hard to trace. When I'm looking for any fluid leaks I use clean white tissue paper. Wrap a turn or two around each nipple or junction and the hydraulic components you can get at before starting the aggressive stand testing. Good Luck.



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post #8 of 19 (permalink) Old Jan 8th, 2006, 7:49 am
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I'm sure you have done this, but just a reminder to take off the fill caps and make sure the vent is clear and blow out the vent hose with brake cleaner.
Bruce C
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post #9 of 19 (permalink) Old Jan 8th, 2006, 11:38 am Thread Starter
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Nope, I hadn't even thought of making sure the vent hoses were clear, and in my conversations with the Service Manager, he didn't suggest that, either. It's not much trouble to get access to the caps, so I'll do that before I do anything else. Thanks!


voxmagna -- I'd wondered about the possibility of what you described - someplace internal in the ABS pump where fluid could end up accumulating, but not be seen. I'm hoping that isn't possible, based on the fact that it seems that I have a rare problem. If there was some internal place fluid could leak into, I'm thinking I wouldn't be the first or only one with mysteriously disappearing brake fluid.

Keeping strict tabs on the fluid level is a good suggestion. I think the easy and accrurate way is for me to keep the digital camera on the shelf next to the bike, and add notes to go with each picture based on mileage and the amount of time the bike sits between rides. It means I need to start riding it more, and I haven't had much confidence in the bike for a long time. I can always hope that whatever was going on to make the reservoir empty out twice is over, but that doesn't seem to fit with my history with this bike!

The one piece of good news that came from yesterday's detailed tear apart and clean is that all the oily accumulation on the front shock came from loose fittings on the oil cooler, and the shock itself is not leaking. I can't believe the stuff I find loose or missing after this bike is handled by "professional technicians." Since the bike was in pieces when the engine was overhauled, and the shock was free of oil prior to that, I'm pretty sure the fittings weren't properly tightened when things were put back together in August.

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post #10 of 19 (permalink) Old Jan 8th, 2006, 2:01 pm
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Your last post got me thinking. You mentioned a lot of grunge on the front shock that you say came from the oil cooler. Well, on the right side of the frame near the steering head (you can see them in front of the tank) are 2 brake line points of connection. The upper line is from the front master cylinder and the lower one is to the front wheel cylinders and it uses a banjo bolt fitting with 2 copper crush washers. Keep an eye on it for leaking.
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