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Oil under the swing arm ...

RJVB

RJVB

GT Reference
Joined
Oct 28, 2008
Messages
1,936
Location
Paris
As you know, there are 2 or 3 hoses that end up at the RHS somewhere under the swing arm, which can cause a nice little oily drip along the rear brake and ABS lines. As a result, I've never been too worried about what's happening there, but now I'm beginning to be. Apparently enough had collected and/or aggregated over the winter to leave 2 or 3 tiny drops on the ground, so I took a paper cloth to the lines, and did some quick cleaning. (I should add that I'd already done a bit in December, to run a zip-tie around the swing-arm -passing above, not over the brake line, of course!- to hold down my hugger.)
That's 2 weeks ago. I just went for another check, and I'm pretty sure there was new oil there. Most of it filthy with road dirt, but some that looked, well, like oil. Yellow, not very dark. This was limited to the middle of the swing arm, where the rear brake line (a metal tube) is held to the arm, though some clearly had run further aft, along the ABS wire.

The hoses arriving from the gearbox and the fuel overflow appear dry...

All this suggests there's a crack or leak in the tubular brake line, and I'm slowly losing my brake liquid. Not very reassuring, but fortunately we have a strong engine brake :)

As far as I can see, the rear master cylinder still has liquid in it, I took off the lower fairing, and shining with an LED lamp, the plastic looks clear yellow on the inside, at least up to the min mark and the black plastic holder that goes around it. But that could just be decolouration or residues clinging to the walls; I don't see much when I screw off the cap (but one cannot really look inside). The rear brake still works though, even if I have no memory of triggering the ABS lately (my pads also about 39k km on them!). I don't see any beading or swelling when I press down on the rear brake pedal. I've already seen that around a bad joint in a rear brake system on another bike (but maybe my pressure is already too far down).

How could one make sure it's the tube? It's bound to be something very small...
Is this a part that can be replaced, or does it require replacing all the hoses that are attached to the tube? (Trying to be positive here, and not assume one would have to replace the swing-arm :blink: )
And a bit of a dumb question: can one just "top up" the fluid in the rear master cylinder?
 
Rene, if the hose was damaged the fluid would pump out, there are some pretty high pressures in brake lines, believe me, you'd loose brakes and have no pedal.

I'd suggest pulling the CARC unit and seeing if there is oil in the swingarm. The holes that hold the clips for the brake line and ABS stuff are pushed into holes in the swingarm that go right through to the inside. Whether this is deliberate I don't know but the result is that if the gear box output shaft seal or the CARC pinion seal go and oil gets into the swingarm it will come out of the clip holes givung warning of oil loss from *Somewhere*.

If when you pull back the CARC any oil comes out have a very good look up the splines of the pinion. If it is oily inside the sleeve chances are the pinion seal has gone. Replacing this requires taking the CARC to bits and a special tool to remove the seal holder. If it is dry up the pinion it may be the gearbox output shaft seal, you need to pull the swingarm to get to that.

Pete
 
RJVB

First, is the oil "oil" or brake fluid? The latter is water-soluble and can be washed away. Any fluid leak is potentially serious and should be investigated and remedied ASAP. But, as brake pads wear, a drop in fluid level in the reservoir is normal and topping up is OK.

If the oil is "oil", does it smell like engine oil, or have a more acrid smell? There have been a very few reports of CARC oil passing the front seal, entering the "dry" swinging arm and coming out where the nearest plastic hose clip plugs into the arm. Is the oil level in the CARC normal? - near the bottom of the filler hole threads after the bike has been sitting overnight on the centrestand.
 
Yeah, I know pressures in brake circuits can get pretty high — probably over 40 bar during emergy braking if the measures on our simulator are an indication.

The thought of a 'hidden' seal going is actually more worrysome than an issue with the brake! But I have the oil halfway down the swing arm, close to where the CARC bolts on. There 's another clip closer to the engine, and there's nothing alarming around it. To reassure myself, and if logic is in any way applicable to an Italian bike, any fluid running into the swing arm from the gearbox would encounter the holes of that clip first, and prefer to "go vertical" at that point...

The smell... I did try to get a sniff, but there's so little, and there's so much dirt in it (looks a bit like black shoeshine!), I'm not sure that whatever I could smell is in any way an indication. I'd say it reminded me of the engine oil smell, and the colour too.

I'll be having the 40000km service soon, I guess I'll have to ask for the suggested verifications, and hope for the best! (I suppose a seal won't be too costly, but I'm not sure I want to know the hours required to change it :-/ )

Supposing it is indeed either seal, how urgent would a replacement be (as in: the dealer probably has neither the seal nor the required tool in stock and we all know what that means)?
 
If the oil levels in the CARC and gearbox are still OK it's probably nothing. The CARCs I've seen with a blown seal tend to loose oil noticeably, easily checked by pulling the filler plug.

Pulling the CARC takes about 15 minutes. Replacing the seal? About 2 hours I'd guess, maybe less if you've done it before and are confident.

Pete
 
Losing oil noticeably means it should be noticeable somewhere ... for example on the ground where the bike has spent more than 2 months in an underground parking, or on the rear wheel rim, no?

The filler hole is the one on the rear end, oriented upwards? Any special instructions for opening and/or closing it again?
 
When you get the filler plug off, take a good sniff. It smells nasty. Then you can tell if that little drip smells the same, or does it smell like lovely motor oil.
 
RJVB said:
The filler hole is the one on the rear end, oriented upwards? Any special instructions for opening and/or closing it again?
Click to expand...

Yes. Wipe it and the recess around it clean before removing the plug. For the most optimistic reading leave the rear wheel unmoved. Moving the wheel causes the moving parts to pick up oil and show a lower level at the plug.

Generally speaking, a "dirty" oil leak is a slow one.

You could try removing the plastic clip near the CARC and see what comes out. Just air, hopefully.

If it is CARC oil but the level is still pretty good, I'd keep riding the bike but check the oil level frequently, given the difficulty Pete outlines for replacing the seal. Then again any leak could be just the front CARC bellows being either damaged or simply not seated properly. Removing the CARC (Very easy) should show that, and replacing the boot should be simple too? Pete may like to comment on that though.
 
I'm going to see if I have the tools here to undo the filler cap. The service manual doesn't mention a torque value, so I'll presume I can just re-tighten it by feeling. (I'll also check/drain the airbox evacuation hose while I'm at it, it's been a while... :oops: )

What I don't get is that according to my understanding of the terms, the CARC is the rear part of the swing-arm, which is below the point where I see my oily drip, at least while the bike is on the centre stand. While riding, it may well be a bit higher, but air flow should direct any running oil aft. In other words, how could oil from the CARC end up where I find it?
Is there a fault with this reasoning?

Edit: yes, I do see it's probably the lowest point where oil can get out of the swing-arm, bummer!
 

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Verdict..

One of my friendly neighbour (from earlier stories) dropped by when he saw me tinkering. As he's a long-term (black market...) mechanic, I let him smell the paper towel I'd used for cleaning the goo under the CARC. Immediate assessment: huile de pont, i.o.w., shaft oil. Bummer. He helped me opening the filler plug (the bugger was damn tight, and I only have basic tools here), and we found the CARC to be filled to the brim. The oil looked clean, not older than the approx. 10k km it's been in according to the bill of my last service.

So I am going to ask to get the seals checked (heh, seals, not joints :oops: ) at the next revision. Meanwhile, I see no reason not to keep riding, and take the trip to the Netherlands I was sort of planning for Eastern (about 2x500 km).

As usual, thanks for all the advice :)
 
I had exactly the same leak. I thought it would be the gearbox output seal with gear oil running down to the cable clip halfway down the swinging arm. I was told it was the carc input seal with oil splashing upwards. They also said they changed the needle bearings/triangleur block bottom of the rear spring. My latest oil leak is left cyclinder engine casing. Other guys say there is a sensor o seal here that needs replacing. Having spent £1000 on oil leaks so far I'm ignoring it.
 
nel said:
I had exactly the same leak. I thought it would be the gearbox output seal with gear oil running down to the cable clip halfway down the swinging arm. I was told it was the carc input seal with oil splashing upwards. They also said they changed the needle bearings/triangleur block bottom of the rear spring. My latest oil leak is left cyclinder engine casing. Other guys say there is a sensor o seal here that needs replacing. Having spent £1000 on oil leaks so far I'm ignoring it.
Click to expand...

Nel,

Your leak at the block is probably the cam sensor. Simple job you can do yourself. Just the o-ring and I use just a very thin film of sealant (clear RTV) on the o-ring to help it seal.
 
RJVB said:
So I am going to ask to get the seals checked (heh, seals, not joints ) at the next revision. Meanwhile, I see no reason not to keep riding, and take the trip to the Netherlands I was sort of planning for Eastern (about 2x500 km).
Click to expand...

As long as the levels in the CARC and gearbox (as I posted a bit earlier) are OK, I'd keep riding and not worry too much. A littel oil makes a lot of mess!
 
Hmmm, the gearbox oil level. Didn't think of checking that as I wasn't aware it has similar oil in it. Wouldn't have known how either, I must admit ... :oops:
 
Just went down to check things after this mornings 95km ride back to Paris. Not really any evolution, but I decided to have a look at the gearbox oil level tonight. I wasn't expecting to need a torx key, and even less a dab of white paint suggesting to keep my hands off (though it doesn't look like a 'seal' that's never been broken before). Am I looking at the right screw/plug??

BTW, I had a peek at the boot covering where I expect the U-joint to be. Perfectly clean, amazingly hardly any street dirt even. I hope that means that the leak, if any, is on the CARC input seal...
 
Shudn't be a Torx bolt there...shud just be regular allen style.

Only two bolts, one on the bottom to drain, and one on the top to fill. Get yourself a flash light as well. Dark hole! Not sure you'll see much and might be hard to tell if she is full. I think an even layer of oil needs to just cover the teeth you can see.

I think.......
 
according to the service manual I have, oil should be up to the rim of the hole.

If it shouldn't be torx, then what was I looking at ??
 
RJVJ,
Your description exactly matches my carc leak that Pete and I found on my Breva 1100, it was a seal in the carc that allowed oil to seep out of the brake line stays. It only takes a few minutes to pull the wheel, then the carc to see if there is any oil in the tunnel past the carc, if there is, new seal time
 
Well isn't that just great, I may finally have a real issue with my bike! :mrgreen:
 
RJVB

At the risk of advocating egg-sucking.........

The gearbox and CARC can use the same oil. I do in mine. Both have in-hex filler plugs, not Torx.

Carc. The filler plug is on the outer rear of the unit, about half way up. After sitting upright overnight the oil level should be at the bottom of the filler plug threads.

Gearbox. The filler plug is on the right side of the gearbox, about half way up. Otherwise as above but the level should be about 10mm lower than the bottom of the threads in in the filler opening.

If the oil levels are OK I'd continue to ride the bike and do any seal replacements when convenient. AISB, a little oil makes a big mess.
 
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