Oil temp gauge off scale

[Huitt3106]

A couple weeks ago I was flying my C model to the avionics shop to have the IFR check completed.  About 15 minutes into the flight I noticed my oil temp reading was high.  I checked the EGT, CHT, and Oil pressure and all was normal.  I decided to descend and divert just in case.  During the descent the temperature gauge didn't drop a bit to indicate any cooling but all other gauges remained normal.   Once on the ground I figured out the gauge wasn't reading correct and tapped it a few times and it moved back to a more normal position.  I flew the airplane back to my airport where my A&P is located  We both looked at it and took the gauge out and cleaned the contacts.  It appeared to return to a normal reading.  While doing this we also found that several of the other original engine gauge needles were jumping around and so we cleaned all of those contacts until they began to act normal again.  

Due to bad weather I hadn't had the opportunity to fly since that happened.  Today, I finally made it to the Avionics shop.  I did notice before I started up this morning that the gauge was showing around 80 degrees (halfway up the gauge scale).  Once I started up and the engine began to warm the gauge started reading high to a point it could not be the actual temperature.  All other readings were correct so I continued on.  Shortly after take-off the gauge pegged full hot like it did in the previous flight.  To me, the gauge is reading as if the scale is off (Cold is 80 degrees and normal cruise is pegged).  Could this be the sensor or the gauge?  What are some simple first steps to take outside of checking all wiring and ground connections?  

Just to note, I have EI engine gauges for the RPM, EGT and CHT.  The oil temp, pressure, and fuel levels are all the original electronic mooney gauges.  I'd like to get a JPI or similar primary replacement as soon as I can afford it but for now I need to make this operable.  

 

Thanks 

Matt

[PJClark]

Is your landing light on when the oil temp is pegged high?  That may happen when someone accidentally grounds the light to the engine rather than the frame.  So check how it's  grounded if you haven't  already.

[Huitt3106]

That doesn't make a difference with the gauge on mine.  I had it on for departure, off in cruise, and on for approach/ landing.  

[TheLachlan]

Check the vernatham valve. My plane did this too while I was training for my PPL and my instructor pretty much shrugged it off thinking the gauge couldnt be working or something along those lines. I didnt think much if it either, I suppose because of his response, my mistake.. BIG mistake. what would have cost maybe $1,500 to address ended up being a full rebuild at around $55,000 or so. Plane has been down over 7 months and should be flying next month again...

[Huitt3106]

Out of curiosity, how was your gauge reading on the ground prior to startup?  This morning its was 35 degrees outside and my gauge was reading 80 degrees when I clicked the master on.  It should have been pegged low.

[TheLachlan]

I believe the gauge worked correctly and there was not a problem with it.

[TheLachlan]

I believe the shop took the probe out and put it in hot water to make sure the gauge worked correctly. It did.

[Huitt3106]

Okay, that makes sense with your case for sure.  I don't think (and hope) that we don't have similar issues.  I'm thinking mine may be more of a sensor/ gauge issue than and actual heating situation.  

[Marauder]

1 hour ago, Huitt3106 said:

Out of curiosity, how was your gauge reading on the ground prior to startup?  This morning its was 35 degrees outside and my gauge was reading 80 degrees when I clicked the master on.  It should have been pegged low.

I would check the accuracy of the gauge and probe as TheLachlan suggests. Your gauge before start up should be reading the ambient temperature or somewhere close to it. If the hot water test shows the gauge or probe has an issue, I would check with Alan Fox or just open an open request to see if anyone has a Mooney cluster gauge set or probe they could sell you cheap. It does sound like an issue either with the gauge or the probe.

I know you indicated that you were considering a JPI down the road. Since you have already have EI primary gauges, if the gauge is suspect, you might consider dropping in an EI primary oil temp gauge if you aren't ready to making the big commitment to the JPI.

 

[Huitt3106]

Just now, Marauder said:

I would check the accuracy of the gauge and probe as TheLachlan suggests. Your gauge before start up should be reading the ambient temperature or somewhere close to it. If the hot water test shows the gauge or probe has an issue, I would check with Alan Fox or just open an open request to see if anyone has a Mooney cluster gauge set or probe they could sell you cheap. It does sound like an issue either with the gauge or the probe.

I know you indicated that you were considering a JPI down the road. Since you have already have EI primary gauges, if the gauge is suspect, you might consider dropping in an EI primary oil temp gauge if you aren't ready to making the big commitment to the JPI.

 

I have thought about the JPI but also don't want to rearrange half of my panel to make it work.  I am quite interested in the new Garmin GI 275 EI since that may would go right where one of my EI gauges are now or where the old MP/ FP gauge is.  I'll take a look at the primary EI oil temp gauge as well as work on the troubleshooting already mentioned.  

 

One other thing, my mooney doesn't have the gauges in the original cluster but in a line at the top of the panel.  Each individual gauge can be unscrewed and slid out.  Are these gauges orignal or from another older Mooney?

 

Thanks!

[Marauder]

I have thought about the JPI but also don't want to rearrange half of my panel to make it work.  I am quite interested in the new Garmin GI 275 EI since that may would go right where one of my EI gauges are now or where the old MP/ FP gauge is.  I'll take a look at the primary EI oil temp gauge as well as work on the troubleshooting already mentioned.  

 

One other thing, my mooney doesn't have the gauges in the original cluster but in a line at the top of the panel.  Each individual gauge can be unscrewed and slid out.  Are these gauges orignal or from another older Mooney?

 

Thanks!

Your 64 C is HIGHLY modified. I don't believe those gauges are factory original (or the yokes or the panel, heck almost anything!  ). Are they? I thought the 60 vintage planes had the square gauge block group on the right side. I see what you mean by the real estate problem. The issue with the GI 275 will be the size. It fits into a 3.5" hole, not a 2.25" one. You would need to do some serious redesigning to get anything else into the panel as it sits today. You need to get the Aspen Max PFD & MFD and then you can dump the ASI, altimeter, vacuum AI and the second CDI. 

 

[Huitt3106]

1 minute ago, Marauder said:

Your 64 C is HIGHLY modified. I don't believe those gauges are factory original (or the yokes or the panel, heck almost anything!  ). Are they? I thought the 60 vintage planes had the square gauge block group on the right side. I see what you mean by the real estate problem. The issue with the GI 275 will be the size. It fits into a 3.5" hole, not a 2.25" one. You would need to do some serious redesigning to get anything else into the panel as it sits today. You need to get the Aspen Max PFD & MFD and then you can dump the ASI, altimeter, vacuum AI and the second CDI. 

 

Haha, yea there is very little original left in the panel (if anything).  The previous owner updated most everything up to 201 style.  I would love to upgrade to the max and add the second mfd to get rid of those other insturments!  Just a matter of putting together the funds!  Wouldn't either the GI 275 or the EI CGR 30 be able to fit in the panel where the MP/ FP and/or RPM gauge is currently?  I haven't measured but I think its close to the 3 1/8 inch hole needed (if I remember correctly).  

[Huitt3106]

I also must say, your panel is quite tidy and definitely not original!  I like it!

[Marauder]

1 minute ago, Huitt3106 said:

Haha, yea there is very little original left in the panel (if anything).  The previous owner updated most everything up to 201 style.  I would love to upgrade to the max and add the second mfd to get rid of those other insturments!  Just a matter of putting together the funds!  Wouldn't either the GI 275 or the EI CGR 30 be able to fit in the panel where the MP/ FP and/or RPM gauge is currently?  I haven't measured but I think its close to the 3 1/8 inch hole needed (if I remember correctly).  

I think based on the size of the gauge, it will fit. The bigger issue is that being all the way over to the right, it will be really hard to see. The font size on the GI 275 has to be pretty small. You may want to see one in person and compare. Also, it looks like it is an expensive gauge (starting at $5,295). I suspect that there will be additional charges for extra probes that you may need.

https://buy.garmin.com/en-US/US/p/719027/pn/010-GI275-08

ENGINE-INFORMATION-SYSTEM-05202839-d316-44ed-9fdd-b257cb391674.webp

[Marauder]

It looks pretty small right in front of the pilot!

[Marauder]

24 minutes ago, Huitt3106 said:

I also must say, your panel is quite tidy and definitely not original!  I like it!

Yes indeed. I am the knucklehead who spent all this money to make it look this way.

Edited January 17, 2020 by Marauder

[Huitt3106]

4 minutes ago, Marauder said:

Yes indeed. I am the knucklehead you spent all this money to make it look this way.

Haha, well the previous owner did anyway!  I see what you're saying about the screen size, that does look rather small.  It looks like the CGR 30 is the same size but a bit cheaper.  I suppose I'd have to see what the best road is from here with some research.  I'm definitely a ways away from doing anything besides getting the oil temp functional for now.  

[Marauder]

2 minutes ago, Huitt3106 said:

Haha, well the previous owner did anyway!  I see what you're saying about the screen size, that does look rather small.  It looks like the CGR 30 is the same size but a bit cheaper.  I suppose I'd have to see what the best road is from here with some research.  I'm definitely a ways away from doing anything besides getting the oil temp functional for now.  

I hear ya. My panel didn't just end up looking like this. I went through phases and I wished I had taken the time to better plan the panel. There were two other updates to the panel before I ended up with what you are seeing now. Take your time. The hard part is that as soon as you think you're happy, one of the avionics companies introduces something new. With the exception of the Max upgrade, I am going to do my best to resist the urge to do another upgrade. But those new GTN products sure do look nice. Inner self: "Stop it you moron!"

[Huitt3106]

1 minute ago, Marauder said:

I hear ya. My panel didn't just end up looking like this. I went through phases and I wished I had taken the time to better plan the panel. There were two other updates to the panel before I ended up with what you are seeing now. Take your time. The hard part is that as soon as you think you're happy, one of the avionics companies introduces something new. With the exception of the Max upgrade, I am going to do my best to resist the urge to do another upgrade. But those new GTN products sure do look nice. Inner self: "Stop it you moron!"

I can imagine it was quite a process to get where you are with your panel!  The main upgrades that I'd really like would be an updated GPS at some point and improved engine monitoring.  For now, I'm pretty happy with what I have.  I'd need a much better job to do very many upgrades!

[David Lloyd]

Many years ago I had an oil temp gauge that pegged the needle after normal indications.  No other symptoms of being hot.  If the oil really was 300 degrees, it would be pretty obvious.  On the ground with the needle still pegged, we measure the oil temp and found 200 degrees or there about.  The next day, normal indications for a while then runaway temp.  Same measurement on the ground, around 200.  Pulled the gauge, had it repaired and worked as expected the next 5000 flying hours.

Could be the sender or gauge.  Err on the side of caution.  Diagnose some on the ground.

[RobertGary1]

6 hours ago, TheLachlan said:

Check the vernatham valve. My plane did this too while I was training for my PPL and my instructor pretty much shrugged it off thinking the gauge couldnt be working or something along those lines. I didnt think much if it either, I suppose because of his response, my mistake.. BIG mistake. what would have cost maybe $1,500 to address ended up being a full rebuild at around $55,000 or so. Plane has been down over 7 months and should be flying next month again...

Easiest test is to turn the master on after the plane has been sitting all night. If the gauge goes to full hot you know there is a short and not an issue with temperature.

-Robert

[Huitt3106]

10 minutes ago, RobertGary1 said:

Easiest test is to turn the master on after the plane has been sitting all night. If the gauge goes to full hot you know there is a short and not an issue with temperature.

-Robert

That is more or less what I did this morning.  I flipped the master on and the gauge showed 80 degrees.  It was 35 outside so I know something is off.  Its not acting like a short, more like the sensor is bad?

[RobertGary1]

1 minute ago, Huitt3106 said:

That is more or less what I did this morning.  I flipped the master on and the gauge showed 80 degrees.  It was 35 outside so I know something is off.  Its not acting like a short, more like the sensor is bad?

I don't have the Mooney Service Manual in front of me but you just need to measure what the sensor is putting out to know if its the sensor or the gauge.

-Robert

[Huitt3106]

1 minute ago, RobertGary1 said:

I don't have the Mooney Service Manual in front of me but you just need to measure what the sensor is putting out to know if its the sensor or the gauge.

-Robert

I would expect those readings are somewhere around here.  I can do a little searching if you don't have that handy.  Thanks!

[carusoam]

Typical failure of the oilT thermistor... is to be showing cold...

Selected this way to not scare the pants off the finance guy flying the plane...

Its only a resistor, so it could be a short, or a ground problem...

PP thoughts only, not a mechanic...

Best regards,

-a-