P

prkaye

Well Known Member
I have oil seeping out my intake ports, some worse than others. The AME next door said this is not normal, and could be a worn valve guide, although this would be very surprising with only 217 hrs on the engine (O-320 from Aero Sport Power).
Pic attached. Any thoughts?

ei2req.jpg
 
Is it really from the intake tubes, or is it seeping downwards from the oil return tubes?
 
Then big ones (such as in the photo) are the intake pipes, right? The AME (A&P) suspects oil might be running down the inside of the intake pipes and seeping out those rubber seals, as shown in the photo.
 
Last edited:
Time to find a new AME. If oil were really leaking out of this joint, as in oil coming out from inside the intake tract, you would have multiple issues, such as massive intake leaks, oil fouled spark plugs, disappearing crankcase oil.....

That oil is running down the intake tubes and puddling in the seam of the intake tube coupler sleeve. Look for weeping rocker cover gaskets or oil return lines.
 
oil return lines

Yes, the oil return lines that are right over the intake tubes are notorious for leaking. Look closely, and the hose clamps are probably either loose or overtightened.

Vic
 
I use automotive spring clamps on the oil return lines, and since they maintain tension they don't leak. Throw the hose clamps in the trash...that's why you never see them used anymore in cars.
 
not sure i understand, please clarify. Are you saying that it's a leaking oil return line that is dripping oil down onto the outside of the intake tube, and there it is running down the intake tube and pooling on the coupler sleeve?

Yes, the oil return lines that are right over the intake tubes are notorious for leaking. Look closely, and the hose clamps are probably either loose or overtightened.
Click to expand...

If I understand correctly, the hose clamps are on the intake tubes, not on the oil return lines... not sure i understand what you are saying here.
 
Last edited:
prkaye said:
not sure i understand, please clarify. Are you saying that it's a leaking oil return line that is dripping oil down onto the outside of the intake tube, and there it is running down the intake tube and pooling on the coupler sleeve?
Click to expand...

Yes. Very common. Check your return line hose clamps. They are probably the most common source for oil leaks on Lycomings.

You'd need two failures for oil to come from inside your intake tubes. Failure 1 = an oil leak into the tubes. Failure 2 - a leak around the hose connections to the intake tubes so the oil escapes the tubes.
 
This is peaking my interest. If it is the oil return line to rubber hose connection that is leaking what's the best way to stop the leak aside from just tightening a loose hose clamp?
 
Is it leaking, as in physically dripping? My O-320 from aerosport has had oil sitting at that intersection since I took delivery of it one year ago. Now have about five hours flying it and it looks the same.

I think the oil came from when I removed the temporary plastic spark plug hole plugs and preservative oil dripped and flowed down the intake pipe. Mine is brand new and looks exactly the same.
 
rocketbob said:
I use automotive spring clamps on the oil return lines, and since they maintain tension they don't leak. Throw the hose clamps in the trash...that's why you never see them used anymore in cars.
Click to expand...

Bob

I think a few people, myself included, would be grateful of a link or pic to exactly what automotive clamp you mean here.
 
walkman said:
Bob

I think a few people, myself included, would be grateful of a link or pic to exactly what automotive clamp you mean here.
Click to expand...

Here's an example:

i-NgSRM35.jpg


There are other types as well, some made from round wire, others that look like regular worm drive hose clamps but with a spring under the head of the gear.
 
Cheap Oil Return Hose Leak Fix

Another way to keep the oil return hose from leaking is to use a little Permatex or Silicone gasket compound on the fittings then snug your hose clamp up. DO NOT over tighten the hose clamp. I have been doing this for the past 15-years without leaks.
 
Absolutely agree with Bob and Lars...perforated band hose clamps are sooo obsolete, and anyway, most are poor quality.

A properly sized constant tension flat spring clamp is perfect for Lyc oil returns. If you just have to have a screw clamp, or for higher pressures, use an ABA embossed band type...Wicks has 'em:

2iudifn.jpg
 
Another option (albeit very spendy) for those wanting a worm drive clamp is the constant tension type like the Gates Green Stripe, with belleville washers under the screw head.

i-DDfXDSD.jpg


Gates part number 32710 fits 9/16" to 1-1/16" OD. Amazon.com has them for the breathtaking price of $5.01 apiece.

They do work well, as long as the specified torque is observed. I use them on all the cooling hoses on my old truck. Killed some stubborn leaks dead.
 
prkaye said:
If I understand correctly, the hose clamps are on the intake tubes, not on the oil return lines... not sure i understand what you are saying here.
Click to expand...
I don't think you completely got the second question answered.
No, they are talking about the oil return hose that has a worm clamp on it. But yes to your first question. It is dripping from this hose connection down onto the rubber sleeve on the intake tube.
 
DanH said:
Absolutely agree with Bob and Lars...perforated band hose clamps are sooo obsolete, and anyway, most are poor quality.

A properly sized constant tension flat spring clamp is perfect for Lyc oil returns. If you just have to have a screw clamp, or for higher pressures, use an ABA embossed band type...Wicks has 'em:

2iudifn.jpg
Click to expand...

Which brings up the inevitable question: What size? I don't think those clamp sizes translate directly to hose OD's.
 
Lars said:
Another option (albeit very spendy) for those wanting a worm drive clamp is the constant tension type like the Gates Green Stripe, with belleville washers under the screw head.

i-DDfXDSD.jpg


Gates part number 32710 fits 9/16" to 1-1/16" OD. Amazon.com has them for the breathtaking price of $5.01 apiece.
Click to expand...

Look again. That is the price for a 10- pack.

Jim Berry
RV-10
 
RV6_flyer said:
Another way to keep the oil return hose from leaking is to use a little Permatex or Silicone gasket compound on the fittings then snug your hose clamp up. DO NOT over tighten the hose clamp. I have been doing this for the past 15-years without leaks.
Click to expand...

The hose fits over the tube with the clamp around the tube. Not sure what fittings get the Permatex or silicone gasket compound.

I have a oil return line that weeped a little oil. Think I may have over tightened the clamp because it weeps more now.

Jim
RV 9a
60 hours!
 
You must log in or register to reply here.