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Yikes! Sudden Mystery Puddle!

aircap

aircap

New member
With the exception of two bouts of snow, this whole winter in Kansas has been lovely, and I've been riding my '78 R80/7 practically daily. Last Saturday (on Kansas Day) the temperature reached 70 degrees and I went for a nice 50-mile ride around the county with a couple friends. Sunday I rode around a bit because I knew a snowstorm was in the forecast for Monday; I put the bike away in the garage Sunday afternoon, hooked up the float charger and put it on its centerstand.

This morning (Friday) when I opened my garage door, I found a puddle of fluid under the bike. I don't think it's oil...it's amber and doesn't smell like oil. Could it be brake fluid? The underside of the engine case is a little grimy, so I can't tell exactly where it's coming from...I had to go to work, so I couldn't take time to mess with it, but I took these pictures. Ideas?

Thanks!

bmw-leak-001.jpg


bmw-leak-002.jpg
 
Is this a /7 with an under-tank front brake reservoir?

If so, likely not good news -- it's not uncommon for the master cylinder to leak past its seals and drain the reservoir, particularly if the bike sat for a long time with little/no brake maintenance and was then put back in service (corrosion in the cylinder rips up the piston seals). :( If this is the issue, time for a mc rebuild or $$$$ replacement.

Most important immediate thing -- clean the frame and anything else painted that the brake fluid flowed over. Brake fluid will take paint off in very short order -- don't just wipe it off -- rinse with water.
 
The reservoir is down under the tank. Will have to take off...I'm off work this weekend, so will dig into it and report.
 
I took off the gas tank and sure enough, the brake fluid reservoir was completely empty. I couldn't tell where the leak was on the MC, though...it appeared to have left more fluid drippings down the right-hand side (from POV of a rider).

I took the whole MC off and inspected it thoroughly, but can't see any evidence of damage or a leak. Guess it's time for a replacement or rebuild, eh? Advice on that? Best source for parts?

Thanks as always, folks!
 
Wonder if it's actually the hose that's leaking...you woulda seen brake fluid all over the engine had the MC leaked, I believe
 
An unlikely possibility

Early in our relationship, my wife -to-be was concerned about a large puddle underneath the radiator of her Honda Del Sol.

Ever the gallant, I did my best, first touching it to see if it was oily and then tasting it.

It was cat urine.

Looks like it would have to be a very large cat, but you can never be sure.

Larry Johnson
El Paso TX
 
If it is the master cylinder seals then the inside of the boot that covers the lever will be wet on the inside, would it not?
 
ljjohns said:
... and then tasting it.

It was cat urine.
Click to expand...

Some things need not be shared on this forum in less there is something that can be gained from this information. Well, I guess this is helpful information in a way. Sniff before taste?

:stick
 
ljjohns said:
Early in our relationship, my wife -to-be was concerned about a large puddle underneath the radiator of her Honda Del Sol.

Ever the gallant, I did my best, first touching it to see if it was oily and then tasting it.

It was cat urine.

Looks like it would have to be a very large cat, but you can never be sure.

Larry Johnson
El Paso TX
Click to expand...

There's a Cheech and Chong joke in there somewhere.:D

Tom
 
"Ever the gallant, I did my best, first touching it to see if it was oily and then tasting it.

It was cat urine."

Too funny! Thanks for sharing. By the way, What does cat urine taste like?

Ed
 
edwarddieck said:
"Ever the gallant, I did my best, first touching it to see if it was oily and then tasting it.

It was cat urine."

Too funny! Thanks for sharing. By the way, What does cat urine taste like?

Ed
Click to expand...

I can go my whole life not knowing that answer. My concern was that it was after he tasted it he knew it was cat urine ... was this not the first taste?
 
Anyway........... . . .. about those parts.

A re-build kit (if that's what you need) is, what, roughly $80?

MAXBMW is number one on my list (Rusty Gill (parts manager) know his stuff).
Hucky's (great pictorial website)
Chicago BMW
Bench Mark Works (Vech)

Or even eBay, with the usual caveat emptor bit.
 
The rubber boot was indeed full of fluid.

I have bought from MaxBMW before...will shop around.

Thanks again!

(And I have had plenty of cat pee moments...LOL)
 
Huckys is quick

I purchased from Hucky's, great price and very quick shipping at a low cost, he is now my regular guy...
When I installed the brand new and oh so tight new o ring I did the following. O ring in hot water for a few minutes, stand piston on end, take dental floss and make two loops, one for each hand (double it up so it won't break) into the O ring and then a bit of silicon grease and it can be pulled safely right over the piston.
As mentioned, be sure and clean ALL brake fluid off the bike. New fluid and bleed, like new! Oh, make sure the hose is in not good shape but GREAT shape. Then you're good to go for many years, or rather good to stop for many...

kurt


Lmo1131 said:
Anyway........... . . .. about those parts.

A re-build kit (if that's what you need) is, what, roughly $80?

MAXBMW is number one on my list (Rusty Gill (parts manager) know his stuff).
Hucky's (great pictorial website)
Chicago BMW
Bench Mark Works (Vech)

Or even eBay, with the usual caveat emptor bit.
Click to expand...
 
So, a new question while I'm still under two feet of snow...

What's the best way to tell whether it's the MC or the hose? Put it all back together and fill it with fluid, then wait to see where it leaks?
 
aircap said:
So, a new question while I'm still under two feet of snow...

What's the best way to tell whether it's the MC or the hose? Put it all back together and fill it with fluid, then wait to see where it leaks?
Click to expand...
Look for tale-tell signs of brake fluid inside the big rubber "box" covering the cable/lever at the rear of the master cylinder and at the rear of the master cylinder piston bore -- if it's escaping through the piston seals, it has to pass through there. Also look for wetness/stains onthe hose, and on the frame below the rear end of the mc.
 
Ah, well the "box" (the big square rubber boot, no?) was full of fluid. Guess that solves that mystery! How big a hassle is the rebuild? Do I need any special tools? Previously kwb210 left some good advice for getting seals in...thanks for that, Kurt!

Also, I have been using a brake fluid that is rated DOT 3/4...I think it's Valvoline Synthetic. Any problem with that? I must admit I find the subject a little confusing. I noticed a sticker under the gas tank that indicated DOT 3 only. Advice?

Thanks again, folks!
 
I just did a rebuild on the master cylinder for my /6. It took longer for the paint to dry on the cylinder body. The old adage about cleanliness applies here.

The only special tools needed will be circlip pliers and a vise. Things that will be useful are some Scotch-brite and a small brass rotary brush that you can chuck up in a drill motor. What I do is use a brush that is smaller than the bore diameter, and wrap a piece of Scotch-brite around it, then chuck it in the drill motor and scrub out the bore. Then I rinse everything well with spray brake cleaner. A very-small diameter wire is needed to clean out the return port.

When reassembling the cylinder I will use a cotton swab and apply a thin film of brake fluid inside the cylinder bore and a film around the new seals, then lightly clamp the cylinder body in the vise in order to use both hands to insert and push down the cylinder piston assembly against the spring pressure and replace the circlip.

The job is not difficult, just take your time and think things out, and remember where everything was when you disassembled it. Not that many parts.
 
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