Rain-testing the Stock CARC Vent - Myth Busting ?

[leafman60]

Ok, after fabricating my own CARC vent and posting the pictorial here I got to thinking. Several people have postulated that the stock vent is bound to let rain into the CARC drive.

I have not been totally convinced of that but I made my vent system primarily because I do a lot of off-road running and creek crossings. Intuitively, I could accept that, if the stock CARC vent got submerged in water while crossing a stream, water could enter the CARC drive.

I decided to do a little test with my almost-new stock CARC vent from my Stelvio. I constructed a little experiment and the results are interesting.

I took the stock vent fitting and screwed it into some tubing. The tubing is connected to a vented collection bottle. This apparatus should collect any water I could get to intrude on the vent fitting.


I improvised a test stand.


I then used a garden hose and sprayer to focus an intense shower onto the CARC vent. I tried several angles of spray for expended periods of time. I am not certain as to what rain or road water exposure the stock vent encounters on the bike but I feel like the water stream shown in these photos matches if not exceeds that encountered on the bike.

First, I tried spraying straight across from the side.



After ample time, maybe 2-3 minutes, I inspected the catch bottle and there was no water inside.



Then, I tried an overhead angle. Again, this resulted in no water in the bottle.



I then directed the scattered spray upwards underneath the vent hood. This did result in a drop or two of water in the bottle after 2-3 minutes.


I then focussed a concentrated stream directly at the underside of the vent hood. This did result in more water in the catch bottle but not nearly as much as I would expect.




Ok, now for a submersion test. I happened to have a funnel that allowed me to slip the tubing through and effect a good seal and thus provide a way of submerging the vent fitting.



I filled the funnel and let it stand. Yes, I obtained the greatest amount of water through the vent fitting while it was totally under water. Again, though, water did not just freely flow through it as I expected.




I removed the hose from the bottle and observed the flow. It was more like a constant and steady drip.


Based on this rather quickly-prepared test, I am not sure I would worry a great deal about riding in the rain with the stock vent set-up. I cannot imagine that even a hellacious rain would result in the kind of water exposure that I created here. Yes, water could get in. Maybe it does. I simply could not detect any water intrusion with a steady fanned spray on the vent fitting. If rain got thrown up under the vent cap, maybe it would enter. I just can't see how that could happen based on where the vent fitting is placed.

Two other points. Perhaps there is a condensation effect going on for some people. As moist air is drawn into the CARC there may be condensation resulting during the normal heat cycle. Second, maybe there is some production variation in the vents. Perhaps some do not perform as intended.

I question whether heat variations would suck rain during operation but perhaps it does.

I do believe that regular submerging of the stock vent could result in water infiltration to the CARC. The degree of that infiltration would depend on many variables including the depth of submersion and time duration of submersion.

In the end, I am glad I made my CARC vent since it will be subjected to occasional submersion. A plumbed vent line may not be necessary for everyone but it will not hurt. Better to have it and not need it than to need it and not have it.

 

[Trophy900]

Hey Leafman - nice experiment and I appreciate your time and efforts. Really this vent type is pretty standard to those used on other manufacturers rear differentials. As a matter of fact, it is almost identical to the one on my Concours 14 so as some have questioned it as cheap or not up to par - I'm not so sure that is accurate. Anyway, these devices are really pretty simple - just a shrouded tube that forces a liquid to have to defy gravity to make it's way past it. I personally believe some of the problem that has been noted with the Stelvio is because it tilts slightly backwards and sits on a relatively flat surface so that under just the right conditions water can travel down the top of the CARC and get splashed up under the shroud. I don't doubt for a minute that the couple of people that have had a problem really did have it occur, I really don't think it a cause for distress, and as you and others have sorted out a simple answer it shouldn't be something anyone looses sleep over.
Thanks again for taking the time to help define it's effectiveness.
Ride Safe,
Jeff

 

[Bisonheed]

Good work, nothing like a home grown experiment

 

[Brian UK]

Remember the CARC is a sealed unit, I wonder what results you would have got if you had used a sealed collector bottle.
But, if you immerse the CARC, the chances are that you will cool it quite quickly, probably producing a small vacuum, which in turn may well suck some water in.

 

[Forseti]

Hmm....

All I know is that after a few days of riding in hard rain over rough surfaces (access roads.. un improved roads etc.) my fluid was white from moisture contamination.

I have since taken a good look at the other possible ingress point.. around the anti-jacking shaft, and found no other way for moisture to get in. Also note that the carc was never submerged.
Perhaps the rapid bounce from "washboard" surfaces and rough gravel/dirt contributed to the water getting in? Dunno.
Perhaps it is possible that my vent is not perfect as well but being that they really are simple I doubt that to be the problem.

 

[Trophy900]

Shrike,
Were able to quantify how much water was mixed in with the oil? Did you allow it to settle and separate or measure the volume? I think that would help us get our arms around what magnitude of intrusion you had.

 

[Luma46]

While I am not convinced that an elaborate CARC vent is required, I need to acknowledge that after riding for 4 hours in a pretty heavy rain, and that was after I picked up my bike in Richmond, the color of the oil was very questionable when I drained it for the first service at about 1200 kms. It was not quite white as in previous post picture, but it was kind of yellow brown, but I thought it was the nature of the factory fill oil.
The CARC typically runs at 50+ C and if you are crossing a creek with CARC Submerged, I can easily imagine that sudden drop of temperature will suck in some water.

 

[Campagman]

Just done the oil changes on my 08 after 5000 miles that included a long stretch in Europe in the rain and some dsily commutes in the wet.

Oil looked fine. But did spot these in an engineering magazine Immersion Proof Breathers
http://brownell.co.uk/our-products/immersion-breathers/immersion-proof-breathers.html

Whats the thread size into the swing arm?

 

[Mi_ka]

How about suction through thermal expansion and then constriction of the air in the CARC: You ride hard in sunny conditions and then you slow down a lot in much cooler intra-rain conditions. Worse yet, you come down from a climb on a mountain so the higher barometric pressure along the cooler rainy air put a positive inhaling force on the breather.
With the Stelvio, a river crossing is in the flight envelope so a rapidly cooling air in semi submerged CARC should easily suck water from a submerged breather.
With the price of the CARC best be sure than busted.

*edit: on second more thorough read I just noticed you have already talked about thermal effects - duh!*

 

[Goodvibes]

Isn't there a seal around the wheel attachment point (axle) where it mates with the CARC housing? Why wouldn't that also be considered a moisture entry point?

 

[Lannis]

Isn't there a seal around the wheel attachment point (axle) where it mates with the CARC housing? Why wouldn't that also be considered a moisture entry point?

If that seal had degraded to the point that it was allowing water ingress under negative pressure, it would surely be allowing oil to pass the other way under positive pressure, and you'd see it dripping down the CARC.

You don't see liquid oil coming out of the breather because it's designed to let vapor out, but keep oil in.

If no oil can get out of the seal, surely no water can get in .... ?

Lannis

 

[kiwi dave]

If no oil can get out of the seal, surely no water can get in .... ?

Ordinary oil seals are designed to prevent egress of oil in one direction only, as I once found out by inserting one in the wrong way around. Thus oil and water could possibly enter past the CARC seal if there was a differential in pressure to encourage it on the way.

BTW, I've never seen a pic of white fluid like Shrike posted, even in the Triumph twins that used their primary chaincase as an engine breather. Looks like somebody substituted milk in the CARC in place of the oil.

 

[Forseti]

Shrike,
Were able to quantify how much water was mixed in with the oil? Did you allow it to settle and separate or measure the volume? I think that would help us get our arms around what magnitude of intrusion you had.

Didnt see this post till now...

No I did not attempt to figure out what amount of water had intruded. Didnt think to. Should have but didnt.

 

[Forseti]

BTW, I've never seen a pic of white fluid like Shrike posted, even in the Triumph twins that used their primary chaincase as an engine breather. Looks like somebody substituted milk in the CARC in place of the oil.

800 + miles on interstate over 2 days really mixes the fluids up I guess. :lol:

 

[stromcat]

Shrike,what damage,if any,was caused to your CARC?

 

[leafman60]

Just done the oil changes on my 08 after 5000 miles that included a long stretch in Europe in the rain and some dsily commutes in the wet.

Oil looked fine. But did spot these in an engineering magazine Immersion Proof Breathers
http://brownell.co.uk/our-products/immersion-breathers/immersion-proof-breathers.html

Whats the thread size into the swing arm?

Interesting. Thread is M10 X 1.5

I just wonder about getting those immersion breathers fully coated with mud and clogging them up. Mud coating is a highly-likely situation.


Update-

I went ahead a constructed my own vent plumbing using a discarded metal Harley brake line and some plastic oil line that I routed up under the tank.

 

[ChuckH]

I just returned home from a trip to the UP of Michigan. This return trip included ~250 miles of pretty hard rain -- hard enough to end up with water in the breast pocket of my Gore-Tex lined jacket. Concerned about possible water intrusion into the rear drive through the vent, I pulled the fill plug to look inside. The gear lube was the normal color and clear, so I did not drain and change it.

However, I did install a vent line since I had the necessary parts on hand. Now I should have no concerns at all.

Edit: Two good things came from riding in that rain.
First, my rear cases did not leak. That is a very good sign.
Second, my speedometer did not quit working. Whatever changes Guzzi has made to either their design or quality control have apparently fixed the problem that had earlier been reported.

 

[Forseti]

Shrike,what damage,if any,was caused to your CARC?

Well.... I have not torn into it but..... (knocking on wood etc) I am now about 4000Km after the incident. Thus far I have no leakage, no play, no noises and doesn't seem to run any hotter than before.

So... to my knowledge it appears to have survived intact.

 

[zoom zoom]

All this speculation regarding water intrusion. Has anybody besides me considered HOW, or more importantly UNDER WHAT CONDITIONS, can water intrude?

Since I am not an engineer, here is my guess. Lets suppose the CARC is hot from running under normal conditions. Now, lets cool it suddenly from a drop in temp along with rain. If you put hot water in a plastic bottle than put it in the fridge, what happens? (In case you never noticed, the sides of the bottle collapse inward.) If that bottle were vented, where do you suppose the vapor would come from, be it air or water? It is called contraction. It is probably only a little. What is too much? Is "just a little" ok? IMHO any water in there is not ok.

The conditions I describe above are exactly what happened to me coming home from the Virginia rally last year. (2011) I am the original owner and that is the first time the bike had EVER seen rain. Fluid was changed upon return home. Milk shake! I now have 17,000 miles on the bike, along with a vent, which was installed before any more rain was encountered. The fluid has been changed a couple of times since then and the bike has seen the above conditions on several occasions. Since the first time, I have never had further evidence of water incursion.

Just think about it. It isn't rocket science! CARC= $4000.00 USD. Vent to beneath the seat can vary but is considerably less than 4 grand.

Now. if you guys want to beat this to death go ahead. Keep telling yourself that it does not happen if that makes you feel better. I'm telling you that it can and will happen under the right circumstances. I'm telling you first hand, not word of mouth because it happened to ME.

You do what you want, but you can't explain it away.

Zoom Zoom,
John Henry

 

[Kelvio]

Not owning a Stelvio {yet} but having alot of riding experience I was trying to look at this objectively and impartially.

It looks as though the CARC is just a check valve of some sort that allows breathing, but no water in, basically.
What would the objection be or obstactles be to screwing in a barbed nipple into the 10mmx1.5 hole, then using a tubing up to the air box or under the seat even as has been mentioned, but then putting the CARC valve on the end of that?

That might give you the advantage of still retaining a check valve just as it was designed, but would remote mount it in a drier position, especially if you routed it into the air box and used some sealant around the penetration that woulld be a possible solution.


Just thinking out loud and trying to help from the outside looking in...this may have already been done before, Im new.