Oil temp low - Check Vernatherm or block oil cooler?

A while back I mentioned that I'd gotten my baffling sealed up to the point where my CHT's never break 400 on climbout. Palm Springs made a liar out of me. 105F OAT and I had to step-climb to 6500' from KPSP going through Banning Pass, where CHT's peaked at around 412-415 before I did so. I see more attempts on the baffling and the possible sealing off of the blast tubes for the mags and alternator.

But the odd thing is, my oil temperature never gets above 150. I did get the 200hp FWF kit, but the oil cooler is the same size as the one that came with my engine (O-360-F1A6 converted to FI), which I had to replace because the core was pierced (unfortunate storage accident).

I'd like my oil temps to be at the recommended 180, so what's the best way to do that? Is the Vernatherm adjustable, or should I just put a blanking plate on a section of the oil cooler and see what happens?

thanks,
-John

Before I did anything, I'd check the accuracy of the temp sensor. Put it in boiling water, should be near 212F, depending on your altitude.

If you have the Vans gauge, from reports and my own personal experience, I have found they tend to run about 20d low.

+1 check the accuracy of the temp sensor/gauge

Hmm.. dunking it in boiling water is going to be a bit difficult since its wires are in a wrapped bundle. I guess I could dismount it

What about blasting it with a heat gun and checking the reading against one of those IR laser readers?

low oil temps

I have low oil temps as well....or so I think. I have a RV-3 with O-320 engine and oil cooler and B&C oil filter set up. I only get to 105 degrees oil temps with screen closed in 90 degree temps. I have not done the boiling water check to date but have pulled the cowling and used the IR temp gun on both the oil filter adapter near the temp sensor and oil filter...shows same temp as oil gauge. I have blocked both the front and back of the air flow on cooler and still cannot get into acceptable heating ranges. Still working but open to any ideas I am missing.

Hmmm - bundle vs oil temp

Just a thought, but you could install an adapter with a thermocouple and see if the oil temps are different. Not as direct, but would be interesting.

- -you know - 2 cents (or less)

Rich Fisher said:

I have low oil temps as well....or so I think. I have a RV-3 with O-320 engine and oil cooler and B&C oil filter set up. I only get to 105 degrees oil temps with screen closed in 90 degree temps. I have not done the boiling water check to date but have pulled the cowling and used the IR temp gun on both the oil filter adapter near the temp sensor and oil filter...shows same temp as oil gauge. I have blocked both the front and back of the air flow on cooler and still cannot get into acceptable heating ranges. Still working but open to any ideas I am missing.

Click to expand...

Rich,

I have no practical experience here yet, but understand engines well (including air cooled) and believe that I understand the engineering behind the O-320 (rebuilding one now). It seems odd that your temps are so low with the cooler fully blocked. You could consider connecting the cooler output hose directly to the input fitting on the engine to eliminate the oil cooler, which would also take the vernatherm out the equation as well. this would eliminate the overcooling potential. If the temps are still low, you need to pull that sensor and test it. Just fill a thermos with boiling water and bring it to the airport with a pan. Pull the sensor (only need a wrench to do this) use a jumper wire to ground the sensor. Put the water in the pan and measure temp with a meat thermometer. Then hold the sensor element in the water, leaving electrical connections above the water line, for 30 seconds and have someone read the temp gauge. If it matches the thermometer, something odd is going on inside the engine.

An IR temp reading on the aluminum boss or oil filter will not necessarily reflect the actual oil temp flowing through the internal passage. remember, the outside surfaces are "air cooled" and aluminum, unlike steel, gives up heat very fast. For all you know, you oil is flowing through the bypass.

I think you will find this to be a sensor, or wiring issue. Don't forget that a loose connection or bad ground will give bad readings also.

Larry