Oil Line Bubble

[tfriest]

I consistently get a bubble in my oil line (the 5/16 line from the oil tank to the engine).

At Heartland, I noticed bubbles going backwards up the line to the oil tank after the Sunday race (when I was loading the car, so it'd been 15 minutes since the race).
I replaced the line and put new zip ties on the fittings to try to make sure they were sealed.
I also drilled a hole in the cap of my oil tank to let air in, since I thought maybe it was creating a vacuum pumping the oil out. That leaked oil all over everything, and I put a shop towel over the hole to try to limit the leakage.
Unfortunately, there was a bubble after the Saturday race (which I bled before Sunday), and another bubble now after the Sunday race.

I do have a return line from the engine (it is a 593). The oil tank is higher than where the oil goes in to the engine, but the line goes down under the axle (my tank is mounted on the back of the frame) and then up to plug into the engine (since that faces up).

Does anyone have any suggestions about what to do so that I don't get the bubble? The current one isn't the full width of the hose, but maybe only 1/3 has oil and 2/3 air (at the top of the bend).

[mmi16]

Give the line enough slack to route it over the axle. Then bleed the air out of the line.

[cjsmith]

In reading your comments, I didn't see you mentioning that you had removed the bled screw on the pump. Any time I removed the line or engine and re connected the oil lines I removed the small screw on the back side of the pump housing to remove any air taped in the pump. If you have too much air in the pump you can loose the prime and can have limited flow until the air gets worked out. Running a little bit of oil in the gas can provide a little extra engine protection.
Let us know what you find.

Chris

[cjsmith]

One additional thought, how much oil was left in your tank at the end of the racer ? If your oil container is smaller than a quart in size, and you are running a lot of oil are you below a 1/4 tank at the end of the race? You could be introducing air from the tank from a low volume and lateral forces pulling the oil to the side of the tank while in the turns. May not be an issue but thought I would bring it up.

[tfriest]

In reading your comments, I didn't see you mentioning that you had removed the bled screw on the pump. Any time I removed the line or engine and re connected the oil lines I removed the small screw on the back side of the pump housing to remove any air taped in the pump. If you have too much air in the pump you can loose the prime and can have limited flow until the air gets worked out. Running a little bit of oil in the gas can provide a little extra engine protection.
Let us know what you find.

Chris

Yes, I bleed the line by removing the screw, which should bleed any air out of the pump too.

[tfriest]

One additional thought, how much oil was left in your tank at the end of the racer ? If your oil container is smaller than a quart in size, and you are running a lot of oil are you below a 1/4 tank at the end of the race? You could be introducing air from the tank from a low volume and lateral forces pulling the oil to the side of the tank while in the turns. May not be an issue but thought I would bring it up.

I can't really see in the tank, but it is roughly 48 cubic inches (that's 84% of a quart?).

The races in Iowa were 20 minutes and 35 laps (roughly 30 minutes), so I doubt it was running very low on Sat considering it didn't run out on Sun. However, there was a long left hand turn (Iowa is a roval and you are on the oval for turns 1 & 2).

That wouldn't explain the bubbles moving up the line that I saw at Heartland, though.