Alternate O-Ring/Gasket/Washer Solution?

I've been chasing a vexing problem on my O-360-powered -6A for a couple years.

I have a persistent oil leak at the oil screen plug - just a dribble - that is messy and irritating. I've tried to nail down the torque exactly ("mating" + 135 degrees) and I've tried tighter and replaced the crush washer and it just doesn't seem to work.

I saw a reference in the Dynon manual to an Earl's Stat-O-Seal washer to use on oil temperature sensors, and some research seems to indicate that this has worked for others with that sensor.

Could a properly-sized version work here? Am I nuts for considering something like this in a place that is so critical? Given that I have an oil filter, is there an aftermarket plug that would work better?

Very frustrated here. Thoughts?

A stat o seal has the o ring on the inside of the metal washer. This may or may not work, as that plug has deep threads and the sealing surface on the sump may be too large to capture the the seal properly. Only experimentation will confirm. Typically when something calls for one of these, that surface is kept pretty tight to the threaded area.

There is a correct orientation for the rounded copper sealing rings used in aviation. Have you confirmed that you are installing them correctly? Also, they can loosen pretty easily, so very tight safery wiring is critical hear to avoid drips. The threads on that plug are very course, so even a few degrees of rotation can create drips. Unfortunate, as this location makes it very difficult to achieve on the 4 cyl engines installed in RVs.

Larry

Apologies for the question - are you really sure it's coming out of that oil screen plug, and not leaking from somewhere above, and dripping down to the plug?

All I got to offer is split side of ring goes toward case. The 135* I believe is for aluminum crush washers, copper 67*. Attached…good luck.

rv8ch said:

Apologies for the question - are you really sure it's coming out of that oil screen plug, and not leaking from somewhere above, and dripping down to the plug?

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I'm about 80% sure. The thing is, it may not be the only leak. I've already done the oil return lines and rocker covers. Those are not leaking.

Oil has been collecting on the flat pieces of angle just aft of the plug. Very close examination has revealed a "bubble" where the oil hasn't QUITE dropped...y'know, the drip before it actually falls....right at the 6 o'clock position of the plug. The trail of the way the oil falls sort of points that way, too, but I can't be 100% sure. I have a plan for this...

I suppose it is also possible that there is oil running down the center of the case, to the center of the bottom of the sump and aft to the plug, but I think that's remote - I dropped the sump this winter to put on a new gasket and there was no trace at all of oil doing that. This leak persisted since I bought the plane two years ago.

Current plan might seem a little extreme, but it's the only way I can think of to be sure: I've got a decent little endoscope with a long-cabled camera on it. I'm going to secure the camera to the motor mounts, facing right where I think the leak is coming from. Then I'm going to run up the motor, do a full RPM test, cycle the prop a few times, and generally try to make it leak. I'll have the screen in the cockpit with me.

Theoretically, I should be able to see it happen, or at least see where it's falling from.

I've noticed some drops on the bottom of the fuel pump, too. The fuel pump itself is brand-new - <50 hours on it - and I'm not seeing any oil where it mates to the accessory case...yet. But it's not aligned with the place where the oil is collecting - it IS aligned with the aft lip of the cowl, somewhat, and I do get some oil collection there, so I suspect I'm chasing more than one leak.

I used the dry spray foot powder method to chase a leak. Clean the engine well with degreaser. Then spray a generous coating of foot powder, the kind that leaves a white dry residue behind. Fly and when you de-cowl you should be able to spot the path the oil takes across the powder film, fairly easily.

Good luck, oil leaks sucks. I have one that I know where it's coming from, it's minor and I am choosing not to address it. I've been told by a few seasoned pilots that if doesn't have a leak, then something's wrong..... lol

BH1166 said:

All I got to offer is split side of ring goes toward case. The 135* I believe is for aluminum crush washers, copper 67*. Attached…good luck.

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I think you see the 10 as the fitting size and not the thread per inch? Example: the oil temp sensor is 5/16-18 thread so it would be 135* per the chart. I have to look up what the oil screen thread pitch is to verify.

Update: the oil screen pitch thread is 1.00-20 so it would be 135* turn from contact for the copper crush washer.

"Current plan might seem a little extreme, but it's the only way I can think of to be sure: I've got a decent little endoscope with a long-cabled camera on it. I'm going to secure the camera to the motor mounts, facing right where I think the leak is coming from. Then I'm going to run up the motor, do a full RPM test, cycle the prop a few times, and generally try to make it leak. I'll have the screen in the cockpit with me."
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The screen cap is under no pressure other than the weight of 8 quarts pushing against it. There is no benefit to run the motor to check the cap for leaks.

To prove the screen cap, reach in and wipe the area well (pay attention to the area over the cap) with a paper towel, and the plate just under the plug. That plate is the mount for the throttle and mixture cables. Cut off a piece of paper towel about 6X4 and roll it up and press it under the cap. Do this three times and if you have oil only on the bottom of the swab then the plug is leaking

It's unlikely a new crush washer is going to leak so be sure to check everything around it. A friend was convinced oil on his fuel pump was leaking from the pump. Lots of folks looked at it, including me, and didn't find the real cause. A pinhole leak in the governor pad gasket sprayed across the accessory case leaving no trail except on the fuel pump. It was discovered when the gasket let go and dumped the oil. He was fortunate to get it on a runway but the engine was toast. Be careful, be certain.

gyoung said:

It's unlikely a new crush washer is going to leak so be sure to check everything around it. A friend was convinced oil on his fuel pump was leaking from the pump. Lots of folks looked at it, including me, and didn't find the real cause. A pinhole leak in the governor pad gasket sprayed across the accessory case leaving no trail except on the fuel pump. It was discovered when the gasket let go and dumped the oil. He was fortunate to get it on a runway but the engine was toast. Be careful, be certain.

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Interesting.

I've ruled out the drain plug leaking. It appears the drips are coming from above the mounting plate for the throttle/mixture cables.

Interestingly enough, I do get the same kind of oil on the bottom of my fuel pump, and it's entirely possible that the oil is coming from that source. Have to investigate further. I'll look into that gasket - I mean, I've replaced every other one....