Very high oil temp

[ltdoyle]

Ok, this might be a little long, but it is kicking my backside.  Last Oct, my engine crankcase (IO-360-A3B6D) had a massive crack under #1 cyl near Waco.  I was able to make it to Waco and land safely.  My A&P/IA and I removed the engine and brought it home where it was disassembled.  There was no metal found and oil pressure never dropped.  The engine had under 500 SMOH.   We obtained a yellow tagged case and reassembled the engine.  It now starts right up and runs great.  However, the oil temperature gauge (OEM analog) will slowly climb in the pattern past the red line (245f) and will slowly drop to just under redline on descent to land at low power settings.  Shortly after landing I can hit the oil filter with a laser temp finder and it will read 185-190f.  I added a second temp probe on the front of the engine with a digital gauge.  It too will get up to 230 or so.  I have since tried two different vernatherms, replaced the factory temp sensor and flushed out the oil cooler.  The original vernatherm end looked great.  I flushed out the vernatherm cavity and reached in and felt with my fingertip and could not detect any burrs or imperfections.  I’m still not convinced if I actually have high oil temperature, or if the gauge has gone wonky.  I’m at a loss what to try next.

[Ragsf15e]

3 minutes ago, ltdoyle said:

Ok, this might be a little long, but it is kicking my backside.  Last Oct, my engine crankcase (IO-360-A3B6D) had a massive crack under #1 cyl near Waco.  I was able to make it to Waco and land safely.  My A&P/IA and I removed the engine and brought it home where it was disassembled.  There was no metal found and oil pressure never dropped.  The engine had under 500 SMOH.   We obtained a yellow tagged case and reassembled the engine.  It now starts right up and runs great.  However, the oil temperature gauge (OEM analog) will slowly climb in the pattern past the red line (245f) and will slowly drop to just under redline on descent to land at low power settings.  Shortly after landing I can hit the oil filter with a laser temp finder and it will read 185-190f.  I added a second temp probe on the front of the engine with a digital gauge.  It too will get up to 230 or so.  I have since tried two different vernatherms, replaced the factory temp sensor and flushed out the oil cooler.  The original vernatherm end looked great.  I flushed out the vernatherm cavity and reached in and felt with my fingertip and could not detect any burrs or imperfections.  I’m still not convinced if I actually have high oil temperature, or if the gauge has gone wonky.  I’m at a loss what to try next.

What does the pressure do as your temperature climbs up that high and then what does it do as the temperature comes back down? I would expect to see the pressure decreasing continuously as the temperature climbs that high. I would then expect to see it coming back up if you get the temperature Down during a decent.

if the pressure isn’t moving in those directions, then the temperature reading is not good.

What are your cylinder head temperatures doing while all this is going on?

[ltdoyle]

Oil pressure drops slightly, cyl temps elevate some

[Ragsf15e]

1 hour ago, ltdoyle said:

Oil pressure drops slightly, cyl temps elevate some

It’s hard to say with the old analog gauges, but if my oil got that hot, the JPI would’ve showed probably 5 to 7 psi or maybe more decrease from say 75 down into the mid 60s.

[Ragsf15e]

3 hours ago, ltdoyle said:

Oil pressure drops slightly, cyl temps elevate some

I’ve heard (but don’t have firsthand experience) that the secondary location for oil temp reads significantly different from the primary.  You indicate that your primary and new probe read about the same? I thought it read that the secondary one which is in front of the engine (i think) Reads high but Im not positive.  Anyway, my thought is - are we sure the original probe is working correctly or is that what you replaced when you said “replaced factory temp sensor”?

[PeteMc]

35 minutes ago, Ragsf15e said:

I’ve heard (but don’t have firsthand experience) that the secondary location for oil temp reads significantly different from the primary.

In a 231, the oil pressure will often be at the bottom of the green as the oil temp rises. In the summer you can be right at the yellow line.

 

[BDPetersen]

Front probe to JPI always read higher on mine.

[Bartman]

Ensure the hoses are hooked up to the oil cooler properly.  I'm not sure how accurate this information is or if I'm stating it correctly, but previous threads have suggested that reversing the oil cooler hoses can cause this issue.  Not sure if this is even possible due to length and fitting configuration, but worth mentioning.

While at it, I would flush the oil cooler and ensure the baffle seals are in good condition.  You said nothing about CHTs so probably not baffle seals.

[Bartman]

By the way, we did the same thing on my A3B6D with a refurbished case due to a crack, and my oil temps are lower than before the repairs.  The only thing we did was have the oil cooler flushed.

[N201MKTurbo]

There is a CPC connector between the gauge cluster and the firewall. Take it apart and hit it with some contact cleaner and see if it gets better.

[cbarry]

I’m not a mechanic, but it sure sounds like a connection/electrical  issue between the probe/s and the oil temp gauge.  Even simple issues such as a bad grounding strap connection can throw off indications  that otherwise would be normal.
 

 

[Yourpilotincommand]

I’d send an oil sample to Blackstone to see if anything looks out of range.

[Utah20Gflyer]

There have been a few times when I’ve bought new parts that were defective.  I would check the temp sensor for normal operation using a heated liquid and another thermostat.  It’s probably fine but just because it’s new doesn’t mean it’s good.  

[Fly Boomer]

1 hour ago, Utah20Gflyer said:

There have been a few times when I’ve bought new parts that were defective.  I would check the temp sensor for normal operation using a heated liquid and another thermostat.  It’s probably fine but just because it’s new doesn’t mean it’s good.  

I'm always surprised when I read ". . . can't be xxx part because it was new/overhauled a few hours ago".  New(ish) stuff makes me more suspicious -- not less.