Oil Pressure/Temp Issue

[Pitch]

I just purchased my bearhawk 4-place last weekend and am having an issue with my O-470R oil temp and pressure. The first thing I noticed was the oil cooler is mounted on the firewall. It also doesn’t have a vernatherm, causing the issue I think?
Has anyone retrofitted a vernatherm or oil thermostat system? I found the mishimoto oil thermostat kit for auto racing applications but I’m sure someone has had this issue already.
Thanks!

[svyolo]

When you have more than one electrical problem that are related, a lot of times they are electrically related. Are both sensors mounted to the same grounding point?

[Pitch]

I’d have to check the ground, but it’s consistent on climbout. High T low P that stabilises in cruise.

[Bcone1381]

It sounds to me like your Bearhawk has a Continental O-470 engine. So your oil cooler not mounted directly to the case in front of the front R cylinder, huh? A vernatherm is a Lycoming thing.

[whee]

It sounds to me like your Bearhawk has a Continental O-470 engine. So your oil cooler not mounted directly to the case in front of the front R cylinder, huh? A vernatherm is a Lycoming thing.

I was thinking similarly. The 470 oil cooler is case mounted unless someone added a second cooler or made a wired adapter. The do have a vernatherm though. The vernatherm is an oil thermostat so if anything not having one would make the engine run colder for longer but eventually the vernatherm is fully open and the oil heat soaks if there is an issue.

What oil are you running?

Can you post some pictures of your firewall forward so we can help figure out what you have going on?

My guess is a baffling issue.

[Pitch]

The stock oil cooler interfered with the cowl, so the builder removed it and mounted an aircraft spruce oil cooler on the firewall. It doesn’t have a vernatherm or thermostat so all oil is circulating through the cooler. 20w50

[zkelley2]

Moving the oil cooler and not having a vernatherm isn't going to effect the pressure. How do you know it doesn't have a vernatherm? On a lycoming you cannot tell by looking at the outside.

I'm also more on the electrical issue as well. Are the gauges mechanical or electric? I had a pressure sender go bad within 10 hours. Hooked up a mechanical gauge to verify everything was correct before replacing the sender.

[svyolo]

I still don't know how my own oil cooler is configured internally, even though I inquired. I know the same about Pitch's. I have used fluid/air and fluid/fluid heat exchangers in a diverse range of things. In some, the orientation of the in/out lines don't matter. In others, the "out" absolutely has to be at the top of the heat exchanger. If not, you need a purge valve at the high point. Unfortunately I don't know how aircraft oil coolers are configured. Mine is called a "drawn cup", which I searched for, unsuccessfully, to find out how it is configured.

For my own build, I just made sure the "out" is at the high point to make sure it functions correctly no matter how it is configured.

But two transducers, grounded to the engine case, giving bad indications, my first intuition is electrical. My first guess is dirty, loose, whatever, ground.

In my own case, I usually start by swapping parts, starting with the most expensive parts first. Just my technique. It is cheaper to starting checking grounds and other electrical connections first. I don't recommend using my technique.

[gregc]

I think there should be some sort of bypass valve. Without it you run the risk of splitting the oil cooler when the oil is really cold.

[whee]

The stock oil cooler interfered with the cowl, so the builder removed it and mounted an aircraft spruce oil cooler on the firewall. It doesn’t have a vernatherm or thermostat so all oil is circulating through the cooler. 20w50

Hmm, that makes it a bit more challenging to diagnose remotely. With the cooler being moved there are several unknowns: Where does the cooler tap into the system. Was the oil temp prob moved? Is the factory stated oil temp range valid for the cooler and prob location?

Consider the massive amount of cooling air the factory cooler gets being at the front of the engine. Perhaps an aftermarket cooler is more efficient than the factory cooler but even if that’s the case I think could be challenging to achieve an acceptable amount of cooling with a firewall mounted cooler.

What oil temps and pressure are you seeing? As the oil temp increases the pressure will drop. It is entirely possible the oil temp is causing the pressure issue. Several mechanics have told me straight weight oil will hold pressure better then a multi-visc so they recommend straight weight during the summer and multi-visc during the winter if the conditions make that desirable. That makes since because multi-visc oil is made with thinner base stock and has additives to thicken it as the temp increases.

[zkelley2]

I have a firewall mounted cooler that does more than ok in our summer Temps and is half blocked for winter.

[whee]

On a Lycoming. Gotta compare apples to apples. Removing the case mounted cooler is a pretty significant design change to the oil system IMO. It would be interesting to see how the factory case mount location was blocked off and how/where the external cooler connects to the system.

[Bcone1381]

Continental O-470, with red arrow pointing to oil cooler.
Screen Shot 2021-04-05 at 8.05.00 PM.png

[svyolo]

A couple of pictures of your remote oil cooler would help. If 50 of us see the pic, maybe one of us will very quickly see the problem. Or maybe not. But it is worth a shot. And it is free.

[Battson]

Oil temps and pressures are definitely related, hotter oil is a lot thinner and flows more easily, thus the pressure drops. This is exactly what the OP describes.
The electrical / sensor issue isn't resonating with me.

[zkelley2]

They are related, but the electrical problem possibility is crazy easy to figure out with a multimeter. Costs nothing. Starting there is by far the easiest and cheapest. From there he can branch into the time consuming and horrifically expensive.

[Battson]

I don't disagree with any of that, however Occam's razor says it'll be tuning the vernatherm (sic) valve. Practically every new EAB install requires this step. Sounds to me like the builder never bothered.

[svyolo]

The fact that it doesn't have a vernatherm makes me think the previous owner removed it - to try to troubleshoot the high oil temperature.

I never heard of tuning the Vernatherm. You might have saved me a troubleshooting headache on my own engine.

[Battson]

Maybe this will help clarify some of the items being talked about here, it's based on Lycomings (which is all I really know) however the names of the devices and how they work are explained, the concepts are the same. It also has some good advice for troubleshooting the kinds of issues being discussed here.

https://www.cessnaflyer.org/maintena...-pressure.html

[Pitch]

Here are the pics. On climbout when the oil pressure dropped to 20, the temp was at 220, increasing speed/Leveling out caused the temp to drop to 180, pressure to 35 or so.