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Sniffle valve for water too?

Bubblehead

Well Known Member
On the way back from Sun-N-Fun to Fort Worth Monday I landed for fuel at Mount Pleasant, Texas and could not get out before ceilings and visability lowered. I tied the plane down, signed up for the crew car and went to dinner and to find a hotel.

Overnight the town and surrounding area got 5 to 8" of rainfall and gusty winds. The next afternoon ceilings were improving so I went to the airport to load up and get on home. When I cranked the engine the prop moved about 20 degrees and stopped, which is definitely not normal. I tried it again but no go. After turning the ignition and Master off I got out of the plane and saw water coming out of the exhaust pipe.

I pulled the prop through about 20 blades and got more water out. Once I stopped getting any water out I tried starting the engine again but could not get it to fire. It did crank but more water was coming out!

Thanks to a good Samaritan mechanic we rolled the plane over to his hanger and put the batter on charge. I pulled the cowling off and removed the spark plugs. All were wet with water. I blew them out and fulled the prop through another 20 blades or so. More water came out!

I have a Superior cold air sump and there are two drain plugs for the air section. I removed the rear one and got about a cup of water out! I jostled the plane a lot to get all the water I could out before putting all the spark plugs back in and finally the bottom drain plug. The engine started and ran normally and a quick mag check told me things were back to normal. I replaced the cowling, loaded up the baggage, disconnected the charger, restarted the engine and flew the rest of the way back to T67 Hicks Airfield north of Fort Worth.

I did not install the sniffle valve when I installed the cold air sump. I'd never had much trouble starting the engine when hot so I did not think I needed the valve and left it off. KISS ruled. I think having the sniffle valve would have allowed the water to drain and perhaps helped me avoid a delayed departure and a lot of work.

My plane is an RV-8 with horizontal induction and the air filter on the baffle ramp on the left side. The driving rain Monday night must have been blowing right onto that filter and the water flowed down the duct through the FI unit into the air sump.

I am also ordering cowl plugs. Those would have helped this situation too. And yes, I realize what hydraulic lock would have done, which is one reason I am writing this! Perhaps someone else can avoid this problem by installing the sniffle valve, cowl plugs, or both, and if they see water coming out the exhaust pipe will reconsider trying to start the engine.
 
Water

Thanks for the heads up! I certainly will be careful to ensure cowl plugs are in place when outside. Let me know if you do the snifflevalve install and how that works. Thanks again.
 
I also have a superior cold air sump and that sniffle valve has failed 2 times on me.
 
WARNING

Yeah - if you ever get water out the exhaust on rotation DO NOT TRY TO START THE ENGINE. There is a good possibility of slugging once the airflow starts and having major damage. Possible: broken - piston, head/barrel, case, bent crank, bent rod, wrist pin - - - just to name a few.

Thanks for posting, I would not have thought that much water could get in there. I have a TG and will take note. Thanks, hopefully you have no damage, but should check (borescope) after a few hours in case a ring land was broken. A leak down test would not hurt asap.
 
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Oil

It would probably be a good idea to change the oil. If you had water on the top of the pistons it is a good possibility that some water "may" have found its way to the crankcase side.
 
Maybe I am completely misunderstanding the issue, but wouldn't a small hole drilled in the air filter intake right in front of the injection servo let any rain/water that entered through the filter drain out instead of filling the servo intake. IIRC the plans call for the hole? Correct me if I am mistaken. Larry

PS My Hanger neighbor had a compression lock due to water from an overnight storm. Had no hole in the intake. Now has a hole. :)
 
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I remember the snorkel instructions saying to drill a small hole in the lowest point in the snorkel.
 
The problem is a hard blowing rain will not drain out a small hole in the snorkel. I have a friend with an RV-8 with the 200 hp I/O 360 that experienced that exact problem. Tail-draggers with horizontal intake sumps need the sniffle valve for sure. I have one in my RV-7A with cold air sump just as a precaution.
 
It would probably be a good idea to change the oil. If you had water on the top of the pistons it is a good possibility that some water "may" have found its way to the crankcase side.

You get a bunch of water in your oil all the time due to condensation and blowby when you shut down. As long as your oil temps hit 180F or higher when flying, this will just boil off. So unless your dipstick reads 2 quarts high because you have so much water, it's not an issue.
 
Water

Pour a few cups of water in you oil sump and tell me that it instantly burns off before potential damage to bearings or compromise the lubricity of the oil....It does take some time at temperature to burn off the condensation of the combustion process. I would change the oil immediately in my engine if water was sitting on my pistons and hydraulic locked my engine. I have seen the damage that can do to a engine. Lucky to not bend a connecting rod.
 
I have drilled a 1/8" size hole at the bottom of my snorkel for this reason. Of course I know to plug my inlet if there is a chance of rain, at least the left side but the drain hole is an insurance for the water not to get to the intake.
 
Rhonda Barrett said that a certain brand was recommended as others were always going to fail. Sorry I don't remember (silly me) what she recommended, but if my Vans part fails she will be my first call. If any one knows, please post.

I just opened a box from Don at Air Flow Performance with a great looking sniffle valve! $25.

http://airflowperformance.com/index.php/product/manifold-drain/

Looks like Don calls it a "manifold drain"

Now that I think of it, this valve requires slight vacuum to shut. With ram air induction there will be a slight increase in MP over lower cowl pressure I would think and thus the valve will not shut?
 
My RV-8 also has the horizontal induction, and I got some water in there once after sitting out in rain overnight. I now make it a practice to pull the prop through at least two complete revolutions if the aircraft has sat outside in any rain. Of course I make sure the ignitions are both off, and the throttle is at idle, and the plane is still tied down when I do this.
 
Now that I think of it, this valve requires slight vacuum to shut. With ram air induction there will be a slight increase in MP over lower cowl pressure I would think and thus the valve will not shut?

Depends.

Assume a "worst case", lots of airspeed down low. A 360 at 2450 sucking through a 3 inch ring and moving at 185 KTAS would have an available intake pressure rise (above freestream pressure) of about 11.5 inches H20. Typical lower cowl pressure (stock RV cowl) would ballpark at 4 inches H2O above freestream. The difference is 7.5 positive, so we might think the sniffle will be open.

However, there is a wild card; pressure loss at the throttle body (and filter if present). I don't have exact values for 255 CFM, but an educated guess says an old RSA-5 sucking through a small filter would result in a negative value at the sniffle, while an FM-200 and no filter would remain positive at the sniffle. A guy with a variable cowl exit might close it, raising lower cowl pressure, and easily closing the valve even with an FM-200.

Good news is that it doesn't matter. The leak can only happen at high airspeed, meaning high power, where the leak is a tiny percentage of total mass flow into the engine. A slight positive leak merely fools the system into supplying a wee bit more fuel, which is perfectly safe for the engine, and the pilot would lean to whatever he wants anyway.
 
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Depends.

Assume a "worst case", lots of airspeed down low. A 360 at 2450 sucking through a 3 inch ring and moving at 185 KTAS would have an available intake pressure rise (above freestream pressure) of about 11.5 inches H20. Typical lower cowl pressure (stock RV cowl) would ballpark at 4 inches H2O above freestream. The difference is 7.5 positive, so we might think the sniffle will be open.

However, there is a wild card; pressure loss at the throttle body (and filter if present). I don't have exact values for 255 CFM, but an educated guess says an old RSA-5 sucking through a small filter would result in a negative value at the sniffle, while an FM-200 and no filter would remain positive at the sniffle. A guy with a variable cowl exit might close it, raising lower cowl pressure, and easily closing the valve even with an FM-200.

Good news is that it doesn't matter. The leak can only happen at high airspeed, meaning high power, where the leak is a tiny percentage of total mass flow into the engine. A slight positive leak merely fools the system into supplying a wee bit more fuel, which is perfectly safe for the engine, and the pilot would lean to whatever he wants anyway.


Solid thought process Dan! The valve open 100% of the time would definitely equal no noticeable difference the leak is so small just might as well drill a small hole in a plug at that point. I agree though the valve will most likely still close most of the time.
 
Not much to explain. The valve failed open on both occasions. a known problem discussed here over the years. Not sure why it happen.

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So what happened? How did you identify the valve as the problem?

And how would one test this valve *without disassembling things like drain hoses and such, or removing the valve from the case* during, say, annual CI?
 
So what happened? How did you identify the valve as the problem?

And how would one test this valve *without disassembling things like drain hoses and such, or removing the valve from the case* during, say, annual CI?

Not trying to drift this thread. if the plane is having issues on idle that would be a clue. You could get a clean hose, slide it over the tube (or actual sniffle valve), then blow in the tube with you mouth. If you can blow in, that means no workie. That is a crude way; but it works. It has detected the issue twice for me.
 
Not trying to drift this thread. if the plane is having issues on idle that would be a clue. You could get a clean hose, slide it over the tube (or actual sniffle valve), then blow in the tube with you mouth. If you can blow in, that means no workie. That is a crude way; but it works. It has detected the issue twice for me.

Thanks...that makes sense. No idle issues here, knock on wood, so hopefully will never have to deal with it, but good to know.

I never thought something as simple as a sniffle valve could fail...isn't it just a little ball in a restrictor kind of fitting, free to move up and down with pressure?

Did you cut open a failed one to see what happened? If it were me... "I got's to know, man!" (Dirty Harry reference intentional).
 
Thanks for all the good input. That is what makes this site so valuable. Here is a summary and some responses.

1) pulling through engine before starting - great idea.
2) drilled hole in snorkle - I must have missed that on the plans, but with a tail dragger will all the water go out the 1/8" hole or will some (most?) run past it into the sump? I think it really takes a low point drain.
3) Sniffle failures - that is why I did not install one originally. I will install and take my chances I guess.
4) Oil change - it's due anyway after 25+ hours of flying to/from Sun N Fun and Virginia Beach.
5) water in oil - the final leg from Mount Pleasant, TX to Hicks was about an hour and the oil got to full temp of about 200F. It is probably all out but am changing the oil anyway.
6) Airflow Performance sniffle valve - it looks like a normal AN fitting. SJordan - Can you post a couple of pictures looking down the fitting? The picture you linked only shows it from the side. Do you think it is more robust than the Lycoming part?

Thanks again everyone.
 
Airflow Perfomance manifold drain

I just received one in the mail. It looks like a regular fitting except the outlet hole has been enlarged and something inserted into it to retain what sounds like a ball bearing in there acting as the check valve. Some of the flare has been sacrificed for the larger hole, but a piece of flared tubing should work fine as a drain. It isn't under any pressure, after all.

Ed Holyoke
 
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