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Swinging Arm Stealth Leak


Theophilus

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What started out as a Saturday reserved in its entirety for a spin on the Twisted Sisters of the Texas hill country next became a day set aside for troubleshooting my brakes and then deteriorated into a sleuthing exercise to determine the source and reason for a fluid leak that ended up not involving brake fluid.

 

THE FACTS:

 

1. This was my first time to wrench on this or any bike, and I don't really work on cars too much.

 

2. Something was making the forward end of strut A in Fig. 1 (end not visible in figure) quite wet with some sort of fluid. The proximity of this strut end to the rear master cylinder and the very real failure of the rear brake late last week had led me to believe that this might be brake fluid.

 

3. The above referenced self-performed rear brake inspection and flush did not reveal any leak in the rear brake system.

 

fig1hf9.jpg

 

4. Transmission, engine oil, and final drive fluids were replaced 7 months/5000 miles ago at a dealer.

 

5. Transmission fluid is full.

 

6. After a bit of head scratching, I suggested to the P.O., who was helping with this exercise, that we open the final drive filler plug and check the FD fluid level. He didn't think that was necessary, but I insisted, because I wanted to mess with as much on the bike as possible while I had him around. He relented, and we broke open the plug. To our surprise, the fluid level was not visible without a flashlight. There was fluid in there, but it was very, very low -- not anywhere near full.

 

7. Wheels were now spinning in the P.O.'s head. He had me loosen the gaiter clamp, and he very slowly pulled back the gaiter at point E in Fig. 1. As soon as the gaiter was the slightest bit away from its mount, cloudy grayish fluid came running out, so we popped the gaiter back on very quickly.

 

8. A visual search for the ultimate source of the fluid that had been dripping onto the front strut end (and the cat) yielded the view shown in Fig. 2, looking forward from the rear of the bike.

 

fig2al9.jpg

 

9. I had been smelling fluid burning on the cat for some while before we tore into the bike this Saturday. Soon after the dealer-performed fluids maintenance, I had smelled and seen a very small bit of smoke from oil dripping onto the cat, though there was no decrease in engine oil level. This went on for a few weeks until I decided to do something about it. The drain canal for the transmission had been left very wet by the dealer and appeared to be dribbling fluid onto the cat. After I wiped this out carefully, the problem seemed to go away for a few months, but in the last few weeks, the smell had come back.

 

10. For some inexplicable reason, we did not check the engine oil level this Saturday. Last check was probably 5-6 weeks/200 miles ago. Haven't been riding too much. frown.gif

 

AN INTERPRETATION:

 

A. Location of drip in Fig. 2 suggested tranny fluid leak, but transmsion full of fluid would seem to make this unlikely.

 

B. Location of drip would seem to rule out engine oil...I think.

 

C. Our thinking is that the seal that is supposed to keep FD fluid in the FD has given out, allowing FD fluid into the swinging arm, where it was never intended to be. The rear gaiter being full of fluid seems to indicate this, and the low FD reservoir and full tranny seem to point to FD fluid as the likely gaiter contents. The cloudiness of this fluid seems to suggest admixture of various greases, courtesy of the drivetrain.

 

D. The drip in Fig. 2 may be FD fluid that has made it up to the front gaiter during hard stopping events that have caused it to run uphill. Since the gaiter is really designed to keep contaminates out rather than fluids in, the egress at this point may not necessarily indicate a bad gaiter(?)

 

PLEASE HELP:

 

(i) Is the interpretation plausible? Likely correct? Almost certainly the case?

 

(ii) What are the likely alternative explanations, if any?

 

(iii) If the interpretation is correct, it would appear that there is a seal between the FD and the swinging arm that needs replacing and that the entire drivetrain from driveshaft rearward needs to be cleaned and re-lubed. Please comment...

 

(iv) If the interpretation is correct, what is the likelihood that this fix could be performed by two guys who have never torn into a drive train and have no special tools, but who also have this board, the BMW shop manual, and the Haynes manual at their disposal?

 

I appreciate any insights and your time in responding if you have some wisdom to share on this.

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The final drive input shaft seal is leaking gear lube into the boot/gaiter. This is very common, and beyond the cosmetic aspect of it, it is usually no big deal. You can have the seal replaced, but the problem may re-occur. Many people just leave it and occasionally clean it off and check the gear lube level in the final drive.

 

Loosen the clamps and pull back the boot/gaiter and see how much gear lube is in it. If just a couple of ounces, then it is in the category of TADT. On the other hand if the boot is flooded and it just pours out, time for a new seal!

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I agree (as if my opinion counts). I tried to put a good eye on the original pictures, and it looks like there is some grime on the front edge of the final drive (or maybe it's just a shadow). Anyway, my '98 RS has been leaking a tad from back there for 60,000 miles.

Now - my question is why did the oil migrate all the way up to the swing arm/transmission gaiter??? Perhaps the previous owner had never opened the FD gaiter to let the excess oil out, and the driveshaft/ujoint stirred it up enough to let it sling forward ?

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It's final drive fluid as previously stated. To be sure it's not coming from the tranny, try this;

 

Change the final drive fluid with something of a different color, ie Amsoil, Royal Purple, or some other fluid type, than what the tranny currently has. At least this will help eliminate that possibility.

 

Go ride.

 

Pull the the boot back at the final drive as Ken H. describes and see just how much is leaking. A few onces or less, no problem. More than that, the pinion seal needs to be replaced. FWIW, you can ride a long time with a leaky pinion seal, like 10 of thousands of miles.

 

Let us know what you find.

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Tommy, what type of final drive gear oil are you using? If you recently changed brands or types that could possibly lead to accelerated gear oil leakage..

 

Some synthetic gear oils do seem to leak out easier than conventional Dino spec gear oils.. Personally I don’t think it has anything to do with whether or not it’s synthetic gear oil but more in line with how much seal conditioner is in the gear oil.. Some of the conventional Dino based gear oil’s do seem to have a lot more seal conditioner in them..

 

Maybe try draining the torque tube then installing fresh conventional Dino gear oil in the final drive,, then ride it a while & keep an eye on it..

 

My GoldWing had a final drive pinion seal seeping oil (not lot but enough to leave spots on the floor when parked).. Kind of a pain to install a pinion seal in that bike so I switched from 75W140 synthetic gear oil to 80W140 conventional gear oil & added ½ ounce of seal conditioner to the gear oil.. The idea was to slow the leak down until I got a chance to re-seal the final drive this coming winter.. That bike hasn’t left an oil spot all summer now.. (unlike the BMW the GoldWing has a torque tube drain opening to allow trapped oil in the torque tube to drip out)..

 

Twisty

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It's final drive fluid as previously stated. To be sure it's not coming from the tranny, try this;

 

Change the final drive fluid with something of a different color, ie Amsoil, Royal Purple, or some other fluid type, than what the tranny currently has. At least this will help eliminate that possibility.

 

Go ride.

 

Pull the the boot back at the final drive as Ken H. describes and see just how much is leaking. A few onces or less, no problem. More than that, the pinion seal needs to be replaced. FWIW, you can ride a long time with a leaky pinion seal, like 10 of thousands of miles.

 

Let us know what you find.

 

Thank you all for the insight (I love this board). I like the idea about filling the FD with another color of fluid. After reading all of this, my main concern is for the lube that is supposed to be on the components inside the swinging arm. I am assuming that the lighter gear oil will have broken down the grease that is supposed to be lubing these components. Two questions remain for me:

 

A. Should I be worried about grease loss on the drivetrain components?

 

B. How big a job is replacing the pinion seal? Too big for me and the P.O. to tear into with only basic maintenance tools? Primary concerns are: (1) need for special tools, etc. that I am likely not to have and (2) any critical adjustments or shimming that need to be "just so" upon reassembly to keep FD or other drivetrain components from eating themselves up.

 

I have posted with a smiley, becuase it sounds like this whole thing may be much less of a problem that I had feared at first .

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It's final drive fluid as previously stated. To be sure it's not coming from the tranny, try this;

 

Change the final drive fluid with something of a different color, ie Amsoil, Royal Purple, or some other fluid type, than what the tranny currently has. At least this will help eliminate that possibility.

 

Go ride.

 

Pull the the boot back at the final drive as Ken H. describes and see just how much is leaking. A few onces or less, no problem. More than that, the pinion seal needs to be replaced. FWIW, you can ride a long time with a leaky pinion seal, like 10 of thousands of miles.

 

Let us know what you find.

 

Thank you all for the insight (I love this board). I like the idea about filling the FD with another color of fluid. After reading all of this, my main concern is for the lube that is supposed to be on the components inside the swinging arm. I am assuming that the lighter gear oil will have broken down the grease that is supposed to be lubing these components. Two questions remain for me:

 

A. Should I be worried about grease loss on the drivetrain components?

 

B. How big a job is replacing the pinion seal? Too big for me and the P.O. to tear into with only basic maintenance tools? Primary concerns are: (1) need for special tools, etc. that I am likely not to have and (2) any critical adjustments or shimming that need to be "just so" upon reassembly to keep FD or other drivetrain components from eating themselves up.

 

I have posted with a smiley, becuase it sounds like this whole thing may be much less of a problem that I had feared at first .

 

Howdy Tommy! First off, a pinion seal, IMO, is a PIA. I'll takle the bike bearing/seal/O-ring, but I'll let a tech takle the pinion. It's not too expensive anyway.

 

Second, make sure you're running the weight that God (or BMW) intended to go in the final drive. 80/90w is what should be in there.

 

Third, Don't worry about the gunky grey stuff. You're going to find that everytime you drain the drive...

 

Fourth, the stuff you found when you pulled the boot back was drive oil mixed with dirt, mixed with all kinds of nasty stuff. It can't really drain back INTO the drive, only out, so don't fret about what you saw exiting the boot.

 

The more they sit, the more apt they are to leak as the seals will tend to dry a bit. Again, unless you're really losing a lot, don't fret. Also, fill ONLY to the bottom of the threads on the drive. Don't overfill! The extra oil has to go somewhere, and it will go out of the vent AND the pinion seal.

 

Good luck!

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Allen,

 

Thanks for the head's up on the pinion seal. My concern was not for the components of the FD, but for the components inside the swingarm, primarily the two U-joints. I presume that their lube has been effectively washed away by FD fluid, and that is my concern.

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Allen,

 

Thanks for the head's up on the pinion seal. My concern was not for the components of the FD, but for the components inside the swingarm, primarily the two U-joints. I presume that their lube has been effectively washed away by FD fluid, and that is my concern.

 

Tommy,

Stick your finger in the drippy oil and smell it. Smell like sulphur? It's gear lube.

Like the others, I'm pretty sure it's your pinion seal and my '96 R1100RT has a slight seep there too. about a tablespoon comes out once a year when I inspect the boot.

 

The excess gear lube will have no effect on the u-joints or bearings in the swingarm. The joints are sealed.

 

Mick

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ShovelStrokeEd

I agree with Mick, no real worries about washing the lube out of the U-joints, they are well protected by external seals.

 

As to changing the pinion shaft seal, it really isn't too bad a job, the old seal can be extracted with a couple of sheet metal screws and some diligent prying/pulling with vise grips. The new seal is just pressed into place with an appropriate seal driver (piece of PVC pipe turned or filed down to the exact OD of the seal - about 0.010". Make sure it is square on the end and then just tap it into place with gentle swings of a large dead blow hammer. The hammer, if you don't have one, will likely cost more than the seal and you can easily substitute a chunk of 2x4. While you have the old seal out, use a flashlight and check the surface of the pinion shaft for scratches or scoring in the area of the seal. You might have to drive it in a bit less to find a clean spot on the shaft.

 

Did I mention this involves removing the final drive entirely and doing the job on a bench with a good vise. It can be done on the floor but it is much, much harder.

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Regarding the effect of gear lube on the drive shaft U joints, there is A LOT of space inside the paralever. You could probably empty two FD's worth of gear oil into it and not have it touch the U joints.

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Yeah, but somehow the stuff is getting all the way up to the front gaiter, so I am guessing there is some sloshing and frothing going on in there. But, since the U-joints are sealed, no worries there, I guess. I am waiting to hear on the splines, though...

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Regarding your problem. You need to take it one step at a time. First, pull the gaiter and allow the fluid to drain. If you get more than a half cup of so of fluid then it would probably indicate the need to replace the seal. If not the I wouldn't worry about it. Regarding the spline lube, I would only do that if I had to take it apart and replace the seal. smile.gif

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Yeah, but somehow the stuff is getting all the way up to the front gaiter, so I am guessing there is some sloshing and frothing going on in there. But, since the U-joints are sealed, no worries there, I guess. I am waiting to hear on the splines, though...

 

Tommy, as a rule any oil leak usually looks worse that it is as oil migrates to the low spots then drips out & makes a big mess..

 

In your case I don’t blame you for trying to determine if the gear oil has washed the splines free of moly grease..

 

More than likely the gear oil you see up in the front gaiter boot got there when the rear suspension was compressed the rear of the torque tube goes high.. Gear oil doesn’t splash worth a hoot so unless it was deep enough in the torque tube to be contacted by a spinning rear U-joint & tossed around I doubt it did any spline washing.. Peel the rear boot back far enough to look into the opening & see if there is any gear oil thrown onto the top inner surface of the torque tube or boot.. If not, then it probably just ran along the torque tube bottom.. If the gear oil looks like it was slung all over in there then probably pull it apart & re-lube the splines & re-seal the pinion..

 

As far a replacing the pinion seal goes I haven’t ever done one in a BMW boxer myself.. Have done a couple of crown bearings & seals but no pinion seal.. I did make a pinion bearing retainer pin socket on my lathe & mill for a co-worker about a year & a half ago as he was putting a pinion seal in his 1100.. According to him the large pinion nut & thrust washer needs to come off the pinion, then the bearing retaining collar (therefore the pin socket).. At that time the seal presses in the bearing retainer from the rear.. Keep in mind I didn’t watch him do it but he did need to borrow both my large & small (pin point) heat guns & said it wasn’t an easy job.. The torque tube pivot bolts also need to be heated to be removed,, if in fact the pinion nut & thrust washer needs to come off those that will need to be heated to 250°f & if the bearing retainer needs to be removed that will require the pinion front housing to be heated to about 250°f & will require a special pin socket that fits the retainer fluted ears.. Like I said above I haven’t done one so maybe there is a short-cut.. Hopefully someone that has actually replaced one will chime in here.. I can’t get in contact with my co-work for a while as he is over in Europe for a vacation..

 

Twisty

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Given the drip at the transmission end of the swing arm I think it may be more likely a transmission output seal leak rather than (or in conjunction with) the final drive pinion seal. I think it unlikely that a pinion seal leak would migrate up to the front of the swing arm in that quantity. The final drive level being low could be due to a leak, or simply not being filled completely at the last service (for instance, the quantity of refill oil indicated in the service manual won't come up to the fill hole, so if the mechanic used the stated quantity to refill then the amount may seem low by inspection.) Also, the apparent correct oil level in the transmission doesn't mean much either as it doesn't take much oil to create the condition you described. The transmission could easily have offered that much up and not appear to be low.

 

Bottom line, I wouldn't jump to the conclusion that it must be the final drive solely by the apparent low oil level. I'd clean everything up and refill the FD to the bottom of the fill hole, and ride a while. If the FD level drops significantly then there's one answer, but if you instead again see a lot of fluid at the front of the swing arm I'd tend to suspect a tranny rear seal.

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Yeah, but somehow the stuff is getting all the way up to the front gaiter, so I am guessing there is some sloshing and frothing going on in there. But, since the U-joints are sealed, no worries there, I guess. I am waiting to hear on the splines, though...

 

All of us are just giving opinions here...if you have oil in the front gaitor, or between the swing arm and the tranny, you've likely got a tranny seal leak.

 

Go back to an earlier post where I suggested using different color fluids. Pulling the swing arm off to check for the tranny seal leak is no biggie, but I'd sure have a manual and the proper tools (ie. torque wrenches with the proper ranges) and some patience. Again, as others have said, a minor leak looks major by the time it all pools at the low point.

 

You'll be fine. The pinion seal is a bigger deal than the output seal at the tranny. thumbsup.gif

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Could a blocked vent cause the fluid to be forced out via the seal?
In theory yes, but in the case of leaking pinion gear/input shaft seal leaks on BMW FD's, there just too many of them that leak/seep to beleive they all have plugged vents. How would they all be getting plugged? The problem exist across three different designs, the 1100's, the 1150's and now some of the hexhead 1200's are seeping there too.

 

It seems the 1200s are leaking in more places than any design to come before. It's one of those areas I don't suppose BMW will ever get right.

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Phil,

 

About your vent plugged comment. I have been exploring the purchase of an R1200RT which is suffering a lot of final drive failures. My trusted BMW trained and certified wrench (has his own shop) seems to think that there is a good possibility that the FD failures on the R1200 bikes is due, at least in part, to the fact that the system is sealed. There is no vent and when the oil gets hot it expands and has nowhere to go but past the seal. After many cycles of hot and cold, the fluid is gone and the bearings fail. This could be an off the wall reason but it seems plausable to me. Gael

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My trusted BMW trained and certified wrench (has his own shop) seems to think that there is a good possibility that the FD failures on the R1200 bikes is due, at least in part, to the fact that the system is sealed. There is no vent and when the oil gets hot it expands and has nowhere to go but past the seal. After many cycles of hot and cold, the fluid is gone and the bearings fail. This could be an off the wall reason but it seems plausable to me. Gael
Interesting theory, but the expansion coefficient of gear oil just isn't that much for the relatively minor temperature shifts we are talking about. Plus there is a pretty sizable air pocket, probably 1/3 of the total volume of the casing, above the gear oil level that would easily compress a bit. And I doubt that despite the lack of a specific vent, the casing is truly air tight.
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Change the final drive fluid with something of a different color, ie Amsoil, Royal Purple, or some other fluid type, than what the tranny currently has. At least this will help eliminate that possibility.

 

This was a clever idea. Unfortunately, the Royal Purple site says in their FAQ that the purple color will not remain after the oil goes into service. It turns plain brown.

 

My plan at this point is to

 

1. Drain FD into a glass oven dish so that I can see the fluid (and through the fluid).

 

2. Drain rear gaiter.

 

3. Check the magnet on the drain plug.

 

4. Attempt to wipe off the forward gaiter and clean up as much of the mess as I can.

 

5. Refill the FD.

 

6. Replace tupperware.

 

7. Ride.

 

8. Check FD and tranny level at 500, 1000, 2000, 3000 miles, and if all looks well, at something like every 3000 miles thereafter.

 

8. Check "rear gaiter contents" to get a feel for how often it needs to be relieved.

 

 

My question now is - what to put into the FD (and does the plan above seem about right)? The Royal Purple site FAQ recommends against additives (like seal conditioner), so I am thinking to go with whatever BMW said to put in there and keep a close eye on levels.

 

Thoughts?

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My question now is - what to put into the FD (and does the plan above seem about right)? The Royal Purple site FAQ recommends against additives (like seal conditioner), so I am thinking to go with whatever BMW said to put in there and keep a close eye on levels.

 

Thoughts

Plain old 80W90 Gear Lube would be my vote.
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O.K. So I took my unfaired RT out for a spin to warm up the FD. Once home, I drained the gaiter, drained the FD, and filled the FD. Prefaced all of this with a rear brake pad change. This all took longer than it should have because I was watching the Indians not finish off the Yankees in Game 3 on the ALDS. I am pulling for the Sox to win the WS again, but I digress...

 

The rear gaiter had maybe a couple of tablespoons of fluid left in it, and we probably let out about a teaspoon the other day. So that is a total of about 7 teaspoons or 0.034 liters in the gaiter.

 

The final drive had just under 2/3 of a cup or about 0.16 liters in it:

 

fluidcrop1ars1.jpg

 

The fluid looks terrible in this photo, but sitting in a glass baking dish, it looked like new oil.

 

I did pull one small shard of FD off of the drain magnet:

 

shardcrop1aif4.jpg

 

shardcrop2aio4.jpg

 

You can see a finished surface in the first shard photo, and a milled surface in the second one. Is finding this on my magnet a cause for concern? The bike is a Y2K model, with about 39k miles on the clock. The previous FD fluid change was back in Feb of this year.

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Is finding this on my magnet a cause for concern? The bike is a Y2K model, with about 39k miles on the clock.

 

Well, yes. There shouldn't be any pieces of hard magnetic material loose in your final drive. The real question is where did it come from. Maybe a chipped gear tooth?

 

I tore down my final drive because of a piece of soft metal I found in my drained oil at 70,000 miles. I didn't find any more or any damage and concluded it was left over from the original manufacturing.

 

Stan

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Ya, that would get my attention as well. It doesn't appear to be a part of the crown bearing (which seems to be at the root of 99% of the oilhead final drive failures) but it still might be a good idea to have a look. It's not that difficult to tear it down far enough to check.

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Tommy, it’s difficult to tell where that piece came from by looking at the picture..

 

It could have come from the oil add container at some dealership,, or could be left over from the initial machining process,, or could be part of something internal..

 

Take the gear oil out into the sun & look for signs of sparkles & metal partials.. Also strain the removed gear oil through a coffee filter or paper towel.. If you find ANY signs of metal particles or other debris in the removed gear oil that would cause for concern.. If you don’t find anything else in the oil then probably not a big concern..

 

If you are worried about the integrity of the final drive just do another HOT gear oil change in another 500 to 1000 miles & if something else shows up you should probably go into the final drive for a look-see.. If nothing else shows up & the rear wheel stays wobble free (do the hand test every bike wash) then it was probably just a leftover or drop in..

 

Pieces or metal usually don’t just show up in the gear oil without leaving a metal grindings trail unless added at an oil change by mistake..

 

Twisty

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