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IO-520 JPI oil temp sensor location?

Tom3holer

Tom3holer

MEMBER
Cape Cod
Happy New Years everyone. It is sure to be an interesting year to say the least.

The oil temp gauge is all but useless in my 73 185 so I bought the JPI probe for my JPI gauge.

Bought a 400509 5/8x18 Jpi probe through Aircraft Spruce which listed it as for all Continental engines but we are not sure if its the correct one. Is there a spot for the 5/8x18 probe or should I try and exchange it?

Tom
 
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I've got to pull the cover off later today/tomorrow and can send you a pic.
 
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Unless your JPI gauge is approved as a replacement instrument, you may consider installing the new probe in the unused oil drain plug location.
 
Which JPI are you using? Some are for primary use and some aren't. If your's is for primary use, you can replace your factory gauge. Otherwise you'll need to keep the factory gauge and call the JPI a 'secondary' gauge.

Either way, the JPI install manual will give you two or possibly three locations to install the temp probe. Why didn't you just get a probe from JPI?

Web
 
I believe the hole for the oil temp probe in the case of my 470K is a 5/8-18, it's just below the oil cooler.
 
I was buying some other stuff from Aircraft Spruce and they are an authorized dealer for JPI so ordered the probe for "all continentals" from them.
The JPI install manual is vague or where to install it and is wrong on a couple of issues like saying the oil temp thermostat is in the rear of the engine.

We did replace the factory one with the JPI and to my surprise it read very low also. I don't think it is an approved replacement so will check tomorrow with JPI. Pete, thats a good idea, I hope the threads are the same. It came up to 138 and pretty stayed there the entire flight which makes the vernatherm suspect.
The engine has only 160hrs and I have had it for perhaps 25hrs so it may have been that way the entire time. We will pull it in a day or so and see if it can be adjusted to close at the recommended 170. 138 is way too low so need to adjust it or replace it I guess.
Tom
 
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Low oil temp, drain the water out of oil sump before starting engine. Seen a widgon that had that as a preflight step.
 
Tom3holer said:
Happy New Years everyone. It is sure to be an interesting year to say the least.

The oil temp gauge is all but useless in my 73 185 so I bought the JPI probe for my JPI gauge.

Bought a 400509 5/8x18 Jpi probe through Aircraft Spruce which listed it as for all Continental engines but we are not sure if its the correct one. Is there a spot for the 5/8x18 probe or should I try and exchange it?

Tom
Click to expand...

Tom,

I think your OEM probe will continue occupying the 5/8" hole near the oil cooler. You probably need the smaller 1/8 NPT probe thats goes in place of one of the plugs near the front of the engine. I have one for you, can do a straight swap.

Send me an email, supercub180@gmail.com

Don
 
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I'm dangerously assuming some data here. Just looked at an IO 520 in a 77 ish 185. The stock temp sensor is mounted in a port just below/aft of the bottom edge of the oil cooler base (the IO 520 TCDS lists oil temps as measured at the 'inlet' so it makes sense). It looks fairly fat, so the 5/8' threads are a good bet. Now you have to get back to the questions from above; is your 'JPI' oil temp system certified for primary use and do you intend on replacing the stock oil temp system already in place? If you are going to replace the existing system and you have a JPI system already installed, simply remove the existing gauge/wiring/probe and install/connect the JPI probe.

If you intend to add the JPI to the existing Cessna system, you need to install the probe in an alternate location. The install manual for the JPI 900 series just says to install the oil temp probe as per manufacturer's data. To me that means the location for the existing probe. And the 900 series is certified for primary use making it legal to replace the Cessna gauge. The install manuals for the 700, 730, and 800 series JPI units list three locations to install the oil temp probes. The recommended is the pipe plug located at the left forward oil gallery, near the base of the prop governor. They call out alternate locations at the right forward oil gallery and on the upper left oil gallery above the prop governor. There is also an alternate location listed as for O 470's at the base of the oil cooler (this won't register until oil is circulating through the cooler). All of these locations are listed as 1/8" or 3/8" NPT. Remember that if you use both oil temp gauges and the probes are in different ports, they WILL read different temps.

Web
 
Sorry I forgot to mention its a JPI 700 and I don't believe its certificated as a replacement gauge for the oil temp.
The forward plugs are smaller as wireweinie said so would have to guy a new probe and am concerned about interference with the baffling.
What We did need to do was confirm the accuracy of the Cessna gauge which was reading very low.
It was indeed, as mentioned above, quite low at 138 in cruise.
I removed the vernatherm today and we hope it can be adjusted to operate properly. There is an adjustment but the fact that's its so far out of wack I wonder if its broken. Will replace the Cessna gauge in its respective location once we get the vernatherm adjusted or a new one. I would like to read the actual temp which you cannot on the Cessna gauge so as be in compliance with Continentals's recommended min oil temp for TO of 75deg and cruising temp of 170deg.

It did modulate the oil at a constant 138-139 during climb and descent so it is functioning.
I did see some info on adjusting it but can't seem to find it at the moment.

Tom
 
Just checked the 700 series manual and the oil press/temp systems are not certified and require that the original instruments be kept and in operable condition.

Web
 
Tom3holer said:
It came up to 138 and pretty stayed there the entire flight which makes the vernatherm suspect.
The engine has only 160hrs and I have had it for perhaps 25hrs so it may have been that way the entire time.
Click to expand...

Tom3holer said:
What We did need to do was confirm the accuracy of the Cessna gauge which was reading very low.
It was indeed, as mentioned above, quite low at 138 in cruise.
I removed the vernatherm today and we hope it can be adjusted to operate properly. There is an adjustment but the fact that's its so far out of wack I wonder if its broken. Will replace the Cessna gauge in its respective location once we get the vernatherm adjusted or a new one. I would like to read the actual temp which you cannot on the Cessna gauge so as be in compliance with Continentals's recommended min oil temp for TO of 75deg and cruising temp of 170deg.
I did see some info on adjusting it but can't seem to find it at the moment.

Tom
Click to expand...
That's a high time Cessna with what is a notoriously poor oil temperature gauge and a very low time factory engine. I'd be inclined to not trust the temperature gauge before finding fault with the engine. The Cessna oil temp is not electric, it has a sealed tube. You might dip the probe in boiling water for a test.
 
Pete,
I replaced the Cessna temp probe with the new JPI probe in the same location and came up with the 138deg on the JPI 700. God knows there is no way to tell where 138 is on a Cessna gauge.

Tom
 
Guess that isn't it then. I always look for the easiest and cheapest solution first. Was it a very cold day when you checked it with the JPI? I'm guessing yes, since it hasn't been warm around here for a while. On cold days the vernatherm may not be able to raise the temperature, even when it's working correctly. There just isn't enough heat generated to raise the temperature particularly with that big oil cooler and the high ram air speed. Try blocking the oil cooler to get the temp up. My 185 runs cool oil temps in cold weather. So, just once I installed the winter front to get the temps up to normal. The oil came up and the CHTs went too hot. The winter front went back to the attic.
 
Hello? Put the probe in a fluid you can heat. Start at whatever temp you think is important, like 75* for bottom of the green. Note the needle position. Try again at another increment, say 150*. Take it up to 200*, 220*, redline, etc. Establish a known value for what the factory instrument is showing you. You'll need to ground the probe in order to make it register. A soup can with some oil in it, a source of heat like a heat gun, an accurate thermometer like a Fluke meter to measure the oil temps... simple stuff.

My oil temp could very easily run as low as 138* in winter if I didn't block the oil cooler. My cooler has a 2" strip of tape across it all summer and at least two strips for winter.

The JPI EDM-700 is not a certified replacement gauge for any temp function including CHT. The EDM-711 is approved as a primary replacement for CHT and oil temperature.

FYI- touch the "oil probe doesn't fit" topic line. https://www.jpinstruments.com/FAQCategory/oil-probe/
 
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Thanks again for all the advice.
I don't think the cool weather has anything to do with it. It was around 40 ish the day I tested it and the Cessna gauge was always very low even on 75deg days which is what prompted me to get the JPI probe.
The 138 came up soon after TO and through the climb to 6K at 100-110mph. Even on the descent it stayed at 138 give or take a few so I am pretty sure its regulating the oil there but will find out in a couple of days when the new one comes in thew mail.
 
stewartb said:
Hello? Put the probe in a fluid you can heat. Start at whatever temp you think is important, like 75* for bottom of the green. Note the needle position. Try again at another increment, say 150*. Take it up to 200*, 220*, redline, etc. Establish a known value for what the factory instrument is showing you. You'll need to ground the probe in order to make it register. A soup can with some oil in it, a source of heat like a heat gun, an accurate thermometer like a Fluke meter to measure the oil temps... simple stuff.
Click to expand...

I do this with every aircraft I get to check accuracy. Most gauges I've tested are only very accurate at one temp usually in the middle range and off a few degrees at the bottom and top of the heat range. The Cub I'm flying now never got above 145F in summer before I checked it and at 200f in a can of oil it was still at 145F. After OH it was spot on between 130 to 160F but off a few outside of that. All mechanical gauges, electric maybe better accuracy?

Glenn
 
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Since your JPI 700 isn't approved as a primary oil temp gauge replacement, maybe your solution is to install a stand-alone unit that is?
Checking my Spruce catalog, I don't see that JPI has one, but they do list the EI OPT-1 which is approved for both oil temp & oil pressure. $500.

I recently replaced the oil temp gauge for my 470K with an old-school cap-tube type unit.
Dunked the bulb in a pot of boiling water & it was right on the money at 212.
Good enough for me. About $125.
 
The Cessna probe is still hooked up and tie rapped out of the way. Once I get the new vernatherm and see what it runs at I will replace the Cessna gauge and probably use the other sump drain plug for the JPI.
 
Tom3holer said:
The Cessna probe is still hooked up and tie rapped out of the way. Once I get the new vernatherm and see what it runs at I will replace the Cessna gauge and probably use the other sump drain plug for the JPI.
Click to expand...

Read the install manual before you put it in the sump drain. NOT one of the recommended locations. Also, not sure if 400509 is the correct probe for the 700. The one described in the install manual has 1/8" NPT threads.

Web
 
The 400509 is a Jpi probe and should fit all models including the 700. You are right its not a recommended location but I don't want to have to buy another probe and the unused drain plug is the same size.
It will read slightly different but knowing now what the new reading will be with the new vernatherm I will make the note of the running temp and apply the delta to other temps.
 
I put the oil temp bulb in the bottom of the sump in my Pitts so the capillary didn't get messed with every time I check the screen. It works great and I don't remember the reading being much different from the old set up, except when inverted the temp goes up about 20 degrees. The 185 will probably not fly inverted.
 
Stock location is just before the oil cooler. Oil gets dumped into the sump after going through the cooler.

Web
 
Had the opportunity to fly today after a stretch of bad weather.
Made some interesting observations

I replaced the old vernatherm with a know good one and much to my surprise it read the same on the JPI in the high 130's
I was very surprised to see this. The OAT was 25-30F at the 2000' altitude I flew at. I duck taped 3/4 of the oil cooler and did the same test. This time the temp came up to 164 or so which is still too low.
Confirmed the oil probe being mostly accurate with a infared heat gun on the oil tank and it read 160 ish matching the probe on the second test.


For those that fly a 185 is it normal to have to cover most if not all of the oil cooler in these rather mild temps to get the oil up to temp?

Thanks,
Tom
 
Tom,

The only thing I cover is the side or gill vents (mine have covers) this makes about a 10 degree change.

Kirby
 
Kirby,

What do you see for oil temps with an OAT of +25 to +30F? Does it not come up to the 170 with no oil cooler covering?

T
 
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Running hard (2400 x 50 ROP) I see mid 170's to 180 in those conditions with the gill covers on, without them I'd be 160 or less and I never cover the cooler unless colder than 10.
 
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