Disappearing brake fluid

ST1300PA Mark

ST1300PA Mark

Joined
Apr 30, 2007
Messages
14
Location
Ottawa Canda
Bike
ST1300PA
I found my brake pedal reservoir almost empty the other day when I was going over the bike prior to a road trip. The brake was still working, but getting a bit mushy. I took the bike in to the local dealer assuming there was a leak somewhere. When I picked the bike up later, the girl at the service counter told me there was no leak, and the fluid loss was caused by air in the brake line. The mechanic who had serviced the bike had already left for the day, so I wasn?t able to get a better explanation of this.
I have never heard of anything like this before. Does this make any sense at all? Can anybody explain it? Or is it more likely I have a slow leak somewhere and the service guy just didn?t find it?

:confused:
 
Doesn't make sense to me. A reservoir worth of air in the brake line?? How did the air get in there. I'm betting a slow leak. I'd have a chat with the tech who did the work. Keep an eye on the reservoir fluid level change should only be because of pad wear.
 
Yea, basically the air was elsewhere in the system and allowed the reservoir to look full. When you used the brakes under real pressure and not just sitting in the shop or on a test ride it forced the air to the top of the system (the reservoir) and you could then see that the system was lacking the proper amount of fluid.

They most likely bleed your brake system to allow the air to flow out and made sure it was completely filled with brake fluid.
 
Mark
It could be air in the lines or a combination of things. "Mushy" does sound like air in lines, ...

... &/or perhaps the bleed valve was loose allowing some leakage and the tech tightened it up(?) It could drip pretty slowly over a long-ish period of time.

If you had a brake line leak you'd likely notice it in your usual parking "spot" and on your bike somewhere.

Also, how much wear do you have on your brake pads? Pad wear will take up some fluid.

The system doesn't hold every much so it doesn't take much to affect fluid level.

More info is needed from the tech IMO. Other, more technically savy STers than I, may have other thoughts.

`Best, Jeff
 
I don't have an explanation, but I had the identical problem on my '04 ABS. About 15 months after I bought the bike, I noticed that there was an exagerated drop of the brake pedal if I released the front brake lever prior releasing the foot brake. I know that a small drop of the pedal is characteristic of the linked brake system, but it seemed to get worse.
One morning I headed down my driveway and had NO rear brake. Checked the rear brake reservoir and dead empty -- no visible fluid. Checked all hoses, calipers, etc and checked the location where I always park and zero signs of leaks.
It was still under warranty, so hauled it to the dealer. They kept it 2 weeks and filled, bled the whole rear system, put a weight on the brake pedal and let it sit for several days to test for any kind of pressure leak and found nothing leaking. I picked it up and have ridden it 11,000 miles since and the fluid level in reservoir has not dropped at all.
Service manager had no explantion at all -- lot of head scratching. I check it monthly and am always vigilant for the "exagerated pedal drop" now.
Regards,
Terry
 
Have you had the recall on the Brake Proportioning Control Valve done? Your symptoms sound exactly like what would happen, although your bike may have a different cause.
 
Well thanks for all the comments guys. After reading Terry's description, I think I have the same situation he had. Very strange. I park the bike in the same spot in my garage all the time, and there is not a drop of fluid on the floor under the bike. As to the proportioning valve recall, does that apply to the '06? I use the dealer I purchased the bike from for service, so I HOPE they would have applied any recalls! I guess all I can do at this point is just keep a close eye on it.
 
DixieFlyer said:
I don't have an explanation, but I had the identical problem on my '04 ABS. About 15 months after I bought the bike, I noticed that there was an exagerated drop of the brake pedal if I released the front brake lever prior releasing the foot brake. I know that a small drop of the pedal is characteristic of the linked brake system, but it seemed to get worse.
One morning I headed down my driveway and had NO rear brake. Checked the rear brake reservoir and dead empty -- no visible fluid. Checked all hoses, calipers, etc and checked the location where I always park and zero signs of leaks.
It was still under warranty, so hauled it to the dealer. They kept it 2 weeks and filled, bled the whole rear system, put a weight on the brake pedal and let it sit for several days to test for any kind of pressure leak and found nothing leaking. I picked it up and have ridden it 11,000 miles since and the fluid level in reservoir has not dropped at all.
Service manager had no explantion at all -- lot of head scratching. I check it monthly and am always vigilant for the "exagerated pedal drop" now.
Regards,
Terry
Click to expand...
Lots of pad wear will cause the brake fluid level to drop close to the bottom of the rear brake master cylinder. If the level was not topped all the way up in the beginning it is conceivable to me the level dropped low enough that you then got air into the system via the rear master cylinder reservoir with resultant loss of rear brake pedal pressure.

In regards to the rear pedal drop - there is no pedal drop in a properly functioning braking system like we have on the ST1300. If you have some pedal drop there is moisture or air in the secondary master cylinder or in the lines leading to and from the proportioning valve and secondary master cylinder. It is important with the linked brake system to replace the fluid as Honda recommends and bleed the system as required. It is tempting to try and bleed it without removing the right side fairing which is required to bleed the proportioning valve and then to not remove and tilt up the secondary master cylinder to bleed it. If the latter is not done it is guaranteed that some air remains in the lines to it or in the SMC itself.
 
dduelin said:
Lots of pad wear will cause the brake fluid level to drop close to the bottom of the rear brake master cylinder. If the level was not topped all the way up in the beginning it is conceivable to me the level dropped low enough that you then got air into the system via the rear master cylinder reservoir with resultant loss of rear brake pedal pressure.

In regards to the rear pedal drop - there is no pedal drop in a properly functioning braking system like we have on the ST1300. If you have some pedal drop there is moisture or air in the secondary master cylinder or in the lines leading to and from the proportioning valve and secondary master cylinder. It is important with the linked brake system to replace the fluid as Honda recommends and bleed the system as required. It is tempting to try and bleed it without removing the right side fairing which is required to bleed the proportioning valve and then to not remove and tilt up the secondary master cylinder to bleed it. If the latter is not done it is guaranteed that some air remains in the lines to it or in the SMC itself.
Click to expand...

Thanks Dave....looks like it's time for me to sit down with the service manual and get ready to bleed the complete system again. Fluid level is OK but still have a sporadic minute pedal drop...(Didn't have the foresight to buy the warranty extension:( :( ) It's time for brake & clutch fluid change so I'll have at it. Thanks for your insight.
Regards,
Terry
 
DixieFlyer said:
Thanks Dave....looks like it's time for me to sit down with the service manual and get ready to bleed the complete system again. Fluid level is OK but still have a sporadic minute pedal drop...(Didn't have the foresight to buy the warranty extension:( :( ) It's time for brake & clutch fluid change so I'll have at it. Thanks for your insight.
Regards,
Terry
Click to expand...

Don't be too hard on yourself because he extended warranty is not worth the paper it is written on if you don't have competent dealer techs to fix your bike properly, you are better off learning how to fix yourself. I would have gotten the warranty in a heart-beat if I would have had any confidence in the mechanical ability of the service departments I have come into contact with. It was the thermostat issue that sealed my opinion on the incredible lack of mechanical understanding they had...Service Manager quote: "The thermostat is never suppose to close all the way"!!!!!!!!!!
 
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