High Oil Pressure

[Mike53]

Looking for some help with my high oil pressure reading on my Hummel engine. Engine has a little over 4 hours and the last time I started it to get the oil distributed in the engine I noticed the oil pressure climbed to 95 psi
at which point I shut it down. I also noted that the indicated pressure when off was sitting at 6psi instead of 0.
I am looking for the most likely problem and then work from there if that does not resolve it.
Any help would be appreciated.
Thanks
Mike

[BRS]

Did you verify your sender and gauge is reading correctly?
Can you plumb in a second gauge temporarally?

[karmarepair]

A POSSIBLE cause of high oil pressure is a stuck pressure relief valve. Pull BOTH of the oil control valves and makes sure they are free in their bores.

A good explainer on the valves http://shoptalkforums.com/viewtopic.php ... 402c698101

And how to get them out if they are stuck https://shoptalkforums.com/viewtopic.php?t=30139 Although I would NOT use White Lithium Grease on them - it CAN harden if left too long. The Chulos at my local NAPA swear by Red Line Assembly Lube.

[WesRagle]

Hi Mike,

I've followed your build. Beautiful paint job!! Looking forward to flight reports.

Looking for some help with my high oil pressure reading on my Hummel engine. Engine has a little over 4 hours and the last time I started it to get the oil distributed in the engine I noticed the oil pressure climbed to 95 psi
at which point I shut it down.

I too have had high oil pressure on my Hummel from day one. Not as high as yours, but high.

I asked Scott Casler about it:

Scott,
The Oil Pressure has been marginally high from the start. I bought another VDO transducer and It produces a slightly higher reading. Last time up after a touch and go the oil temperature was about 180 but the oil pressure went to 80 PSI on takeoff. Is there an easy way to bring the pressure down a bit? Or ..., should I just not worry about it? As a side note, while on the ground I can bring the pressure down by goosing the engine.

To which he replied:

I wouldn't worry about the high oil pressure. You can lower it by changing the spring on the rear relief valve.

The thing that bothers me most about it is that high oil pressure probably results in higher oil temp. I flew this morning with OAT of about 40 Deg. F and the Oil Temp still hit 200 on a 2500 ft climb, that with a lot of oil cooler. At some point I will attempt to lower the pressure some.

Wes

[GraemeSmith]

The thing that bothers me most about it is that high oil pressure probably results in higher oil temp.

It's usually the other way about -

High oil temp thins (single weight) oil and the pressure drops. Even with multigrades - they eventually fail to hold viscosity when really hot.

High pressure is usually indicative of cold thick oil (or poorly adjusted relief valves)

[GordonTurner]

Or…electric oil pressure senders aren’t the most reliable thing. Before anything else I would suggest temporarily, or permanently, adding a direct reading oil pressure gauge.

[WesRagle]

HI Graeme,

Yes, my oil pressure drops as oil temperature increases. What I was referring to was the extra heating of the oil due to the rear oil-relief valve being set too high. It's that valve that controls the oil pressure with hot oil and high engine speed.

Attached is a page scanned from "How to Rebuild Your VOLKSWAGEN Air-Cooled Engine". The "dual oil relief valve" system is the system that applies to must of us. If you look at the last full paragraph in the left column, that's what I had intended to convey.

Wes

[Mike53]

I want to thank all for the replys. I figure since I should do an oil change anyway ,I may as well remove the oil relief valves and see if that is the problem and if not try replacing the sender .Thanks also for the sites to visit for more info .
Also thanks Wess re-paint job. The jury is still out about painting your plane. I had the convenience of knowing how to spray paint as i painted about a million cars at the ford motor co.
No question it adds weight and in my case looking for the perfect shiniest paint job possible ,added extra weight.
In the end I am happy with doing it. Next time i will use base coat clear coat. I got talked in to the enamel because it was cheaper to buy. Enamel has to go on heavier to achieve the shine.
In base coat clear coat the base is put on just enough to give the colour (easier to control the metallic)and then the clear gives the shine .
Cheers
Mike

[pappas]

The oil pressure on my turbo is normally about 80-90 at startup depending on the outside temp. Once it starts to warm, it drops to 50-60 and under cruise 40-50. If it never goes over 100, you shouldn't have any problem and shouldn't burst your oil cooler.

I don't have any issues with the oil temperature getting to 200-220f. Sonex says 240f is the redline. Moisture in the oil doesn't boil off until the oil gets over 200 or so anyway. The increased oil temp can be an indication that it is taking heat from the engine. Both airflow and oil circulation help to cool our engines.

[NWade]

If it never goes over 100, you shouldn't have any problem and shouldn't burst your oil cooler.

Please be aware that many of the Oil Pressure senders max out at ~80psi. They do not tell you when they are off-scale high, so you may think your pressure is maxing at 80psi when in fact it has gotten much higher and your oil cooler is ready to pop. Ask me how I know! :-P

I recommend checking your oil pressure sender to make sure it can read 120-150psi. If you ever see 100psi or more, it is likely that your Engine has a problem.

The most common cause (and what led to my oil cooler bursting) is a stuck oil pressure plunger. When assembling the engine don’t simply rub light motor oil on them and see if you can move them down their channels without getting stuck - verify that they smoothly and easily slide all the way to the end. You may think you’ve slid them to the end with your finger, but the retaining plug & spring can push them even farther, into areas they wouldn’t go with your testing. Consider inserting them into final position with their spring, and even though it’s a bit of a pain, remove the plug and spring afterwards and make sure each plunger can/will slide back down. This is wayyy less of a pain than cleaning up an engine bay that’s had a quart or two of oil sprayed all over it by the prop blast!

—Noel
Sonex #1339