Rotary valve oil overflow

32 posts in this topic

Posted

Hi All,

My rotary valve oil reservoir started to over flow a couple of weeks ago when I was flying. I have an Avid with the inverted 582. I removed some oil and tried it again. It was overflowing after an hour or so of flying. There was no sign of water but I decided to replace the water pump and rotary shaft seals anyway to be sure. There was no sign of water in the oil that was drained out of the rotary valve and no grooving of the shaft under the seals. My coolant and passages were super clean. I put everything back together and started it today. It seems to run smoother than ever although there should not have been a difference with the seal change. After running for 15 minutes or so it appears that the rotary valve oil was rising again in the reservoir.

Does anybody have any ideas about what else could be causing this? I have probably flown around 40 hours in this Avid over the past 3 months with no problems until I was pushing a little hard to catch up with a friend and running at 6300-6400 rpm and 115 mph indicated but only for about 10 minutes then back to 6000 rpm. I don't think that could have caused the problem but maybe I guess.

Thanks,

Dan

Avid C Speedwing with 582

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Posted

That's a new one. My first thought would have been water too. It's a closed loop system in order for it to rise something has to be getting in there. Is the vent in your cap open so it can breathe? 

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Posted

Yes, the pin hole vent in the top of the cap is where the oil eventually comes out and ends up getting into the cockpit and all over the floor, back side of panel etc. I have the oil that I drained a few days ago in a bottle to see if any water separates but so far it looks just like the 2 stroke oil that has always been in there. After running today I pulled out enough oil to bring the level back to half full in the reservoir. I will get some run time on the ground tomorrow morning to see what happens.

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Posted (edited)

My first guess would be water, but if your oil isn't getting cloudy, then maybe not.  Not sure that it's possible for crankcase pressure to get into that area, but if you engine is mounted inverted, is it possible that air/fuel mixture is being pushed from the crankcase and filling the area around your crankshaft gear (what drives the water pump shaft) with air?  I know if you aren't careful when you put the oil in to start with, you can trap air in there on an inverted engine and the gears will eat themselves up in a short while.  Just now looked at the blowup of the crankcase in my LEAF catalog, and there are 2 O rings/seals on each side of the gear on the crankshaft.  If one side is letting air by, that could perhaps displace the oil in there and push it out through the bottle.  Sorry for the bad news,..  If I was going to check this on my engine, I would see if I could get oil to go into the lower port with a clear hose going off the upper port so I could see if air bubbles are coming out as the oil goes in.  That is actually about how I fill them when I remove and replace an inverted 582 engine.  If you have a Kitfox with a "right side up" engine, disregaurd everything I just said.;-)  JImChuk

PS  just reread your post after I posted my reply, and if it was me, I wouldn't run the engine till I knew the gear area didn't have air In it

Edited by 1avidflyer

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Posted (edited)

I did bleed the air from the case using the plug that is at the bottom of the case or, since the engine is inverted in this aircraft, the highest point on the case besides the hose going to the reservoir. I will check in the morning to see if there is air at the bleed plug.

BTW, I did smell the oil after draining to see if there was any hint of fuel in it and I did not smell any traces of gas.

Thanks, Dan

Edited by dav8or

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Posted

You may not smell any fuel residue in the Rv tank as the heat would possibly percolate it out.

what colour oil are you using for your engine?

use a different colour in your Rv system,if the colour starts to  change in the Rv to the colour in the fuel its bad news followed by a crank rebuild.

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Posted

I use clear reinforced dishwasher line. I had to stand my plane on its nose to get the air to finally purge.

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Posted

The oil level was back down this morning to where I think I started Saturday morning. I didn't see any air come out of the bleed plug this morning so I ran it for about 20 minutes with some high speed taxis and some full throttle crow hops to make sure I covered the full rpm range that I can get on the ground. I think what I saw on Saturday was simply thermal expansion causing the oil level to rise slightly. I never really paid attention to how much higher the level is right after shutdown because I don't usually pull the cowling off after a flight until I had this issue pop up. Hopefully the seal change has corrected the problem.

Has anyone else ever noted how much the oil rises in the reservoir from cold to right after shutdown? Also does anyone know of a reasonable place to buy a new rotary valve reservoir? Seems like it is such a special part that Rotax has them marked way up because they know you can't get anything like it anywhere else. Looks like $80 for that little plastic tank which kind of feels like highway robbery.

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Posted

I've never noticed the oil level rise after running the engine.  I usually ran a bit over the full mark, and never had oil coming out the top of the bottle.  JImChuk

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Posted

If the oil level went down it probly had an air bubbles in the system.

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Posted

If it's fuel and oil getting past the seal from the crank case your running your engine lean. We know what happens when 2 strikes go lean. Kind of a scary think to have happening. 

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Posted

I really doubt it is fuel/oil from the crankcase. With the speed that it was rising, from half full to full tank in an hour, I would expect to see it in the egt's. There was also no fuel odor at all in the oil. There did not appear to be any contamination at all. I will keep it in mind though. The engine is running very smooth and the egt's are nearly matched

There is a possibility that the reservoir may be plumbed backwards. I never noticed the tube projecting from one of the hose connections before. I looked at another old tank sitting in the hangar and noticed the in and out markings. I cannot see markings on the tank that is mounted due to the bracket. I am going to pull it out to have a look which means I will have to drain it again. If it is backwards, it has been that way for a long time (probably around 100 hours running time on this engine and a couple hundred on the 532 before it).

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Posted

If you look at an exploded view of the 582 crankcase, you see the gear and O ring/seals are in the center of the engine.  It has nothing to do with the seals at the ends of the crankshaft that could allow air to get into the engine.  I don't believe this will cause a lean condition if the end seals are holding.  The bottle is just a resivior for holding extra oil.  It does not have a flow/circulation through it.  If you just fill the bottle when you are filling the system, you will trap air in the gear area, and then bad things can happen.  When I fill an empty system, I unhook the hose from the bottle that goes to the lower port between the carbs.  Usually I slide another hose over this hose so it is about a foot higher than the bottle.  That gives more head pressure to help the oil flow.  Put a funnel into that hose and fill till oil comes out of the other hose and back into the bottle.  At this point, you should be able to hook the hose back on the bottle and fill the bottle to the full mark.   It helps to have clear hoses so you can see if air bubbles are coming out.  JImChuk

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Posted

Jim, The O-rings you are talking about are preventing pressure from entering RV gear area or keeping the oil from leaking out of the housing? Do we have that much positive pressure below the piston? I was thinking it would be more likely to leak RV oil into the crankcase if the o-rings were bad. I think I read that in a Rotax advisory somewhere.

The 2 bottles I am looking at have one connection away from the fill cap that has a tube projecting up into the bottle to almost the fill line. The connection that is directly under the cap is open to the hose at the bottom of the tank. That should create a very slight convective flow through the bottle if they are connected properly at the engine.

Dan

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Posted

I would think that those O rings do both.  Keep oil in, and air/fuel mixture out.  There has to be some pressure in the crankcase, cause when the rotary valve closes, and the piston comes down, fuel mixture is pushed up into the cylinder for the next combustion cycle.  Keeping oil in is mostly fighting gravity, I would think.  Oil is way thicker than air, so I would think the air is likely to leak first.  I forgot about the bottle having different levels above the hose connections.  I'm sure they should be lower with lower, and higher with higher.  That would probably help air to come out also.  Don't think there is much if any flow however.  Just to be clear, I never really said that these O rings 'are' the cause, but threw that out as a possibility.  I do feel that it seems likely though.  What else explains what's happening?  This system and the oil injection system aren't connected, and oil level seems to go up.  I think if it was me, I would drain the entire system, and make sure I got all the oil out.  I'd put a drain hose on the lower fitting and blow into the upper hose even to help it flow all out.  Then I would refill the entire system with the funnel and extra length of hose.  Lift the tail high and see if you can get any air bubbles out, and try the bleed screw as well.  Then see if it seems to make more oil the next time you run it.  By draining and refilling, you will be starting off fresh with a clean slate so to speak.   JImChuk

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Posted

I understood it as a possibility and was just trying to think it through. At the moment I don't think that is the problem.

I think I have the answer. It has taken a long time but something is settling out of the oil in the bottle that I used when I removed the RV shaft for seal change. I will give it more time to see how much clearer it gets.

I was wrong about the tube in the rotary valve oil tank. It goes all the way to the top of the tank inside. My guess now is for bleeding air that might get into the system. I swapped the lines on my tank and refilled like Jim suggested from the lower line until it flowed over the top of that internal tube then filled the tank to the fill line. BTW the tank that came in my Avid does not have the arrows indicating flow like the newer one does but it does have the tubing inside.

I ran it again for about 20 minutes after the hose swap on the tank and the level did rise about 1/2 inch in the tank when I checked immediately after shut down. After 5 minutes or so it was back down close to the cold mark. I will check it again tomorrow when it is completely cold again to see if it is exactly on the fill line where I started today.

Thanks, Dan

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Posted

I haven't seen the rotary valve level change to any noticeable amount in my upright installation,there is very little oil in the rotary valve circuit,oil doesn't expand much but air does!

1/2 an inch variation would have me worried

double check for air lock

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Posted

Not sure how many times I should check for air but I get only oil coming out of the bleed plug each of the 3 times I have checked so far. Might be a little less than 1/2 inch rise. I didn't have a measure at the time. I will run it some more. Any small bubbles of air should work themselves out if there are any. I will be monitoring it closely for the next several runs.

This is not the first time I have done this oil change. I did it several times when I had the 532 on this plane. Every time I had to remove the engine to reset points and then once once this 582 when I put in on to replace the 532. I just never paid attention to the oil levels right after shutdown before.

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Posted

I don't trust the bleed screw to get the air out completely myself.  It's a small hole, and oil is relativly thick.  If there was no oil in the system, and the oil level came up from the bottom, while the air went out the bleed screw, then maybe.  YMMV.  JImChuk

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Posted

Just don't fall out of the sky. if you do have air in the system more than likely it will eat the inside of the engine out. Saw that happen last year on a friends Challenger. They Changed oil after 50 hrs on a brand new engine and it only took 7 hrs to blow to pieces.

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Posted

Just a thought - how would you get the air out that would be trapped just above the hose fitting in the case? That area is above the bleed screw.

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Posted (edited)

If anyone ever gets Really Really desperate for one of those little plastic oil bottle thingys - I think I saw one on my "boat anchor" Kitfox 532 head,  just above the big round thingy (generator) in the back, which was hooked to a starter thingy - I will attempt to remove it or see if it leaks.  Is that what you are talking about with 2 hoses into the bottom of it?   EDMO

Edited by EDMO

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Posted

Just a thought - how would you get the air out that would be trapped just above the hose fitting in the case? That area is above the bleed screw.

I doubt that a tiny bit of air at the top of the gear would hurt anything.   Dusty makes a good point in his post about air expanding much more than oil when heated.   JImChuk

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Posted

If anyone ever gets Really Really desperate for one of those little plastic oil bottle thingys - I think I saw one on my "boat anchor" Kitfox 532 head,  just above the big round thingy (generator) in the back, which was hooked to a starter thingy - I will attempt to remove it or see if it leaks.  Is that what you are talking about with 2 hoses into the bottom of it?   EDMO

That is the one. I need to replace one that has visible cracking on a bottom corner.

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Posted

If anyone ever gets Really Really desperate for one of those little plastic oil bottle thingys - I think I saw one on my "boat anchor" Kitfox 532 head,  just above the big round thingy (generator) in the back, which was hooked to a starter thingy - I will attempt to remove it or see if it leaks.  Is that what you are talking about with 2 hoses into the bottom of it?   EDMO

That is the one. I need to replace one that has visible cracking on a bottom corner.

Mine is old, but I will try to check it this week to see if it is still good - then we can get together on shipping, etc.  EDMO

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