Oil Temp Gauge M20c

[Gpettit1986]

Hey everyone,

I am new to the forum and to aircraft ownership as well. Long story short I just purchased a 63 C about a week ago and have been flying it a lot. We were on our way back from NJ to VA yesterday and I noticed the factory oil temp gauge was reading extremely high ( almost redline) I was at about 8500 at 21 mp 2400 rpm. I immediately started my decent in to my home airport opened cowl flaps and reduced power. The needle never moved. While I was concerned about the oil temp reading so high I was getting conflicting information from the JOI 830 which was reading oil temp at about 188-193 during climb and steady 185 during cruise. 
 

When I landed I checked the factory gauge again and it was still close to redline. I figured it was a malfunction and I would verify this morning by checking the temps with a cold engine.  Well I went out this morning and both gauges were at 82 and when I warned the engine up the factory gauge climbed way faster than the JPI and they never evened out. 
 

CHT during return trip 350-360

oil pressure was consistent and in the green.

[Mooney Dog]

Id be more than willing to bet the factory gauge is inaccurate, but so long as its working and not in the red, id trust what the jpi says.  

[ShuRugal]

Factory gauges are pretty flakey. I had to have my oil temperature probe replaced shortly after buying my 64 C, and I always had weird behavior out of the needles until I replaced them with a JPI this year.

Sent from my Pixel 3a using Tapatalk

[Raptor05121]

My oil temp gauge always pegged out for the first 5 years I've owned it. Oil temp and pressure and coincident- if you had red line temps, you'd see lower pressure. I'd chalk it up to something being almost 60 years old

[Utah20Gflyer]

I have the exact same situation except I only have a JPI 800.  I trust the Engine monitor over the factory gauge so have ignored the problem for a while.  I understand the oil temp sender is pretty delicate and if over tightened it will break something internal and then read over temp all the time.  I'll be replacing mine when the plane goes in for some other work next month.   I think the sender is sub 200 dollars and access is very good so hopefully it will be an easy and cheap fix.  

[Hank]

Check the wires from your factory gage. Mine went to redline right after an oil change. Turned out the safety wire had shifted and grounded the thermocouple. Replaced the safety wire, no trouble since (~9-10 years now).

The joys of airplane ownership!

[MikeOH]

19 hours ago, Hank said:

Check the wires from your factory gage. Mine went to redline right after an oil change. Turned out the safety wire had shifted and grounded the thermocouple. Replaced the safety wire, no trouble since (~9-10 years now).

The joys of airplane ownership!

Thermocouple or thermistor?

I would think a shorted thermocouple would read 0 (BWTHDIK)

[Guest]

On 8/27/2021 at 3:13 PM, Gpettit1986 said:

Hey everyone,

I am new to the forum and to aircraft ownership as well. Long story short I just purchased a 63 C about a week ago and have been flying it a lot. We were on our way back from NJ to VA yesterday and I noticed the factory oil temp gauge was reading extremely high ( almost redline) I was at about 8500 at 21 mp 2400 rpm. I immediately started my decent in to my home airport opened cowl flaps and reduced power. The needle never moved. While I was concerned about the oil temp reading so high I was getting conflicting information from the JOI 830 which was reading oil temp at about 188-193 during climb and steady 185 during cruise. 
 

When I landed I checked the factory gauge again and it was still close to redline. I figured it was a malfunction and I would verify this morning by checking the temps with a cold engine.  Well I went out this morning and both gauges were at 82 and when I warned the engine up the factory gauge climbed way faster than the JPI and they never evened out. 
 

CHT during return trip 350-360

oil pressure was consistent and in the green.

Look for a loose connection at the oil temp probe or bad wiring at the probe.

Clarence

[carusoam]

Read Alex’s post twice…

Regarding the back-up between OilT and OilP….

They are designed to show you… if one goes bad, the other has to show some reality…

If your oilT goes to redline… the oilP is going to drop off the scale to the low end…

If they are both flaky… it’s land now time… 

PP thoughts only, not a mechanic…

best regards,

-a-

[markgrue]

Many times someone does not hold the center post of the oil temp probe when they tighten the nut on the ring terminal and it breaks the thermistor in the probe.  Sometimes it goes open sometimes it gets shorted.  They are relatively cheap.  You can check it with an ohm meter.  clip the leads on it and note the reading.  put it in a pot of boiling water and watch the reading.  it should change consistently and not jump around.  I do not remember the readings but consistency is the key.

 

Mark

[cliffy]

How old is the gage? Factory original I'll bet?  They get old and dirt on the mechanism which causes all kinds of issues,

Question- Why do you suppose Lycoming requires "calibrated gages" to be used on the break in of a freshly overhauled engine?

If you break in a new engine WITHOUT calibrated (with in 1 year) (in the airplane) gages you can't technically sign off the engine "IAW factory overhaul procedures" 

Ask your FSDO that question and see what answer you get :-)

Oil Pressure gage is a primary gage IF it pegs out and stays there realistically and legally the airplane is grounded until it gets fixed 91.205 a, b  (if its installed it has to work correctly)

All technicalities I know but violations are written on technicalities

BTW IF you have the old style 6 pac gage set "all in one" block of gages you can direct swap them for the 6 pac with individually removable gages there by being able to get just 1 gage fixed as opposed to having to over haul all of them when one fails. Some shops will only overhaul the entire 6 if they are "all in one: block type. 

If you have the "OLD" style and it has a Cannon plug on the back it is a straight screw one off, screw the other on deal. There is a SB on this subject. 

Other new manf gages are available for the 6 individual gages rathe than an overhaul of a 50 year old gage.