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Oil Temp IO360 RV-7A

P

Pat Stewart

Well Known Member
After building 4 RVs last week I purchased number 5. I am starting to think I have an oil temp problem. Yesterday I flew the aircraft, OAT was around 90f, climbed out to 4500 feet and OAT was 82f. Cylinder temps were around 350-360f. Here is what is bothering me, oil temp peaked at 155f. The seller had taped up about 25% of the oil cooler and stated he did that to help raise the oil temps. Also around every adel clamp on the engine mount I see what looks like a little brown stain, at first that did not bother me but I am know wondering if it is heat related.

Here in North Texas I would have expected 200f on climb settling back to 180 in cruise. Any thoughts would be appreciated.
 
Pat, I am assuming it has the standard Vans oil cooler (Niagara 20002a) mounted on the baffle? And with your experience, you have already checked the temp sensor to see it reading ambient before start up?

Just thinking out loud - lets assume the engine timing is not retarded and its performance is nominal - - and if the cooler is standard Niagara 7 row, and the vernatherm is stuck closed, then the oil temp behavior would act the same as the temperature rose after TO up to the peak on climb but then would drop lower than 180F when leveling off in cruise.

If cooler is way larger than the 7 row standard, AND the VT is stuck closed, then it might not reach the same peak and would stay low and go lower on cruise.

Hmmm, curious indeed.
 
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Yes, standard Niagra from Vans mounted on rear baffle. I did not look at the ambient however after reading your message I went back and looked at a screenshot of the Skyview taken some time in the past with a cold engine. Oil temp was 65f and OAT read 72f.
 
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Pat Stewart said:
...OAT was around 90f, climbed out to 4500 feet and OAT was 82f. Cylinder temps were around 350-360f. Here is what is bothering me, oil temp peaked at 155f.
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Check the location of the temperature probe. My guess is that you'll find it installed in the viscosity valve hole. There is no actual flow there.
 
Pat Stewart said:
Thanks guys, Dan you wouldn't happen to have a picture/diagram would you.
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Sure. This is a standard AC-style oil filter adapter on the back of a standard accessory case. The oil temperature sender is in the WRONG place.

 
I've had the same issue as Pat discribed. I also taped up a coule inches of the cooler and found pretty good response. Cruise at about 175 degrees and climb 180-200 - All in Florida summer.

But, when I look at Dan's pic I think my pressure sender is mounted in that hipe he points to.

I'll have to take a closer look amd report back.

Curious on your outcome Pat.
 
Thge brown stain around black adels is normal. It's what they do. Even sitting around without running.
 
Thanks everyone, thanks for the picture Dan. Alton all is well here, how is Dothan, we really miss all our Dothan friends and the weekly visit to Hunts. Say hello to everyone for us.

Pat
 
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Looks like the sender is in the correct location. I removed the tape from the oil cooler and flew it again. The OAT was 94f climbed to 3500 with an OAT of 84f. Oil temp climbed to 157f and that was it. I think this is starting to look link a bad Dynon oil temp sender but would still appreciate feedback.
 
Thanks Dan I will do that next. It is interesting that the oil temp read the same with the oil cooler 25% taped up as it did when tape was removed.
 
Pat Stewart said:
Thanks Dan I will do that next. It is interesting that the oil temp read the same with the oil cooler 25% taped up as it did when tape was removed.
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It is not uncommon for a sender to fail/wear at the extended end of the range. They use a bi-metallic spring that can lose it's temper. The fact that you are a few degrees off at ambient would make me suspect the sender. Hot water and a candy thermometer will confirm.

Larry
 
Here?s a post from the Dynon forum:

Title: Re: Oil Temp Sensor?
Post by Dynon Support on Apr 6th, 2009 at 6:11pm
________________________________________
A simple bad ground on the sensor would make it read low. The temp goes up as the resistance goes down, so extra resistance with a bad ground would lower the temp.

A bad ground between the sensor ground and the EMS (ie between the engine and the battery) can make the sensor read high, since this causes a voltage drop across the wire, which is the same as a lower resistance.

With a voltage drop, the sensor gets much more inaccurate at higher temps. It only takes a few mV at 220F to cause a 10-20 degree error.

The easiest way to test for this is to turn off your alternator. This will stop the ground current and will show you if it's causing an issue.

We don't publish the full characterizations of the sensors - we consider that proprietary data - but here are a few points that should help you along:

49.4F 1540 Ohms
103.5F 390 Ohms
150F 155 Ohms
220F 45 Ohms
280F 22.1 Ohms
 
Looks like it's the sensor. With the old sensor I had a 10 degree spread between the oil temp reading and the CHT readings while cold in the hangar. Installed the new sensor last night and both read the same. Just need the weather to clear so I can fly it and see what the real reading is. I talked to the oil sample folks who just finished an oil sample, they said there is no indication in the sample that the oil got too hot. Also CHT readings were always fine so I am pretty sure all is well. More to come after I fly it.
 
Weather cleared and we had a chance to fly this evening, everything normal, oil temps exactly as we expected. Thanks for all the input.

Pat
 
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