Oil flow on initial prime

[ccm]

We have a BOTTOM mounted oil cooler and have just filled, primed and turned over the engine. Although there is oil pressure there does not appear to be any oil feeding from the pump into the cooler. Both cooler pipes are devoid of any oil.

Can anyone tell me if this is normal behaviour for the initial prime of the engine (as on page 60 of the AeroVee 2.1 manual)?

Thanks
Craig

[MichaelFarley56]

That's very strange Craig. You said you are getting oil pressure?

When I was first turning over my engine I had to re-fill my oil pump gears with lithium grease in order to "re-prime" the pump, but that was a result of not getting any oil pressure. By the design of the system, all of the oil should be going through the cooler as the pump picks the oil up from the sump. So yes, you should have oil in the lines.

Perhaps you have some sort or air bubble in the cooler? You could always take both lines off the cooler and fill the cooler manually to ensure there's no issues.

[ccm]

Thanks for the help Mike. We have filled up the oil cooler manually, have started the engine up and it seems to be running okay. We are definitely getting oil pressure from around 7psi while cranking to 25 psi at 2000 RPM running. I've yet to go much above 2000 RPM due to not having the plane well anchored.

Can you tell me what oil pressure you normally get at idle with cold oil and at around 2000RPM?

Thanks
Craig

[mike.smith]

I was getting 45-50 psi under those conditions. Your numbers sound low. Do you have a digital or mechanical display?

Mike Smith

[ccm]

It's a digital display: MGL Stratomaster Velocity E1.

[mike.smith]

:shock: :D

It's a digital display: MGL Stratomaster Velocity E1.

Make sure you have the right setting in the setup. I have the MGL Mini Extreme. I had mine on the wrong setting in the oil pressure set up and it showed 2 psi when a mechanical gauge showed 45 psi. the instructions were confusing about what setting I should use, so I contacted the company, told them the sender I had and they gave me the correct setting. Just a thought.

There are two acceptable locations for a mechanical gauge or sender on the top of the engine, so you could attach a mechanical gauge to check. I did that before contacting the company to verify I was getting the correct oil pressure. The NPT fitting size is quite small so it took a little looking on Amazon to find a gauge.

Mike Smith

[MichaelFarley56]

For what it's worth Craig, I've had very marginal luck with my MGL Stratomaster Ultra XL and the digital oil pressure display it has. I went through around 4 different VDO sender units, each grounded to the engine case but each had 4 completely different (an inaccurate) oil pressure readings. Eventually I found a pressure sender from a different company (can't remember which...I'll try to find it) that was somewhat accurate but my biggest piece of advice is to do what Mike said; hook up a mechanical gauge for best results! Had I known, I would have installed it right into my panel somewhere.

To answer your question though, when my oil is cold I will normally see around 80-90 psi during initial idle power settings (1200 or so RPM). I make sure my oil is at least 100 degrees F before takeoff and at that time I will see oil pressure around 80 PSI, falling to around 55-60 PSI in cruise of 3200 RPM and oil temps of around 170-180 degrees.

Pressure drops after landing since the oil is so warm, but even then it will be 20-25 psi.

If your oil is cold and you're running 2000 rpm, a pressure of around 25 psi seems awfully low. I would be worried about it dropping too low once the oil warms up. Before you make any changes or get worried however, use a mechanical gauge to see how accurate your numbers are.

Let us know!

[ccm]

Thanks again for the help. We'll try opening up the oil pump and re-grease it this weekend. If that doesn't sort it out then a mechanical gauge sounds like the best option. I'm reasonably sure the issue is with the oil pump at the moment though.

[ccm]

We got this solved today. The oil pump cover was inverted and turning it the correct way up instantly achieved an oil pressure between 40-50 psi.

I guess this is just one of the unknowns if you buy an engine built by someone else. It had never previously been started but had gone through a few owners.