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Oil pressure spikes

Veetail88

Well Known Member
Folks,

I have an IO-360 in my 8 and had an oil pressure event a few weeks ago and haven't seen it since, although I'v only done a few short local flights since.

I was on my way back to 57C (East Troy WI) from KMGM (Montgomery AL), flying along at 6500' about 2 hours into the flight when my AFS 4500 sounded an oil pressure alert. Looking down it was indicating the pressure was 117 PSI, where normally it's around 86.

I was probably 40 or 50 miles from the nearest airport so the pucker factor went way up.

So I decided to keep going while constantly looking for emergency landing sites (slim pickins there) and stayed pretty keenly focused on the motor parameters. My oil temp stayed put in the green and none of the other temps were abnormal.

As I went, the pressure very slowly came down to about 95 psi which made me feel quite a bit better and so I flew past the first landing spot. By now I was getting pretty close to Louisville (I was pushed well east avoiding a convective system moving across the area) and airports were more plentiful so I kept going.

The oil pressure climbed again to around 112 and slowly went down again and kept fluctuating between around 99 and 110 psi. Again, everything else stayed normal. I sort of thought I might have a sending unit problem, but the pressure kept fluctuating and didn't just go to some out of range point so I'm not too sure one way or the other.

I kept going, navigating the front edge of the weather which started getting me closer to my acceptable minimums and together with the oil pressure problem I was thinking I'd better get her on the ground as I was up to two strikes!

I squeezed between the nasty weather and the Cleveland Class Bravo and set my sights on KMIE (Muncie IN) for a stop, fuel, investigate the oil problem and lunch. (there is a very nice restaurant right next to the FBO).

Safely on the ground I checked over everything I could see and found nothing out of the ordinary. Oil level fine, no oil on anything under the cowl, not a clue about anything.

With a full belly, full fuel and about a 1 hour leg left I launched, figuring I'd again keep a very close eye on things.

Well the oil pressure went to 86 PSI and stayed right there until I got home. I've done a couple of short local flights since and again, everything stays normal.

Anyone able to postulate on this?

Thanks for any help.
 
I have had a couple VDO pressure sensors go bad, giving erratic and high indications on my Dynon. Last replacement got an upgrade to a Kavlico sensor, no problems since.
What display and sensor do you have?
 
I agree that the prime suspect is the sensor. It is just a spring and diaphragm. When they wear, they routinely read high. If it is a VDO sensor and it likely is, I would replace it and watch closely.

Larry
 
pp. 7-50 and 7-51 here
http://dynonavionics.com/public_htm...-_REV_AB_-_CUST_DOC_GUIDE_INSTALL_SKYVIEW.pdf

show the new Kavlico sensors and the old VDO sensors. The VDOs suck, IMHO, and demonstrate exactly the failure mode you describe: intermittent, noisy and high.

I'll bet dollars to donuts if you open the cowling, you'll find the fuel pressure and oil pressure senders are VDOs. Do yourself a favor and upgrade to Kavlicos for both of them.
 
pp. 7-50 and 7-51 here
http://dynonavionics.com/public_htm...-_REV_AB_-_CUST_DOC_GUIDE_INSTALL_SKYVIEW.pdf

show the new Kavlico sensors and the old VDO sensors. The VDOs suck, IMHO, and demonstrate exactly the failure mode you describe: intermittent, noisy and high.

I'll bet dollars to donuts if you open the cowling, you'll find the fuel pressure and oil pressure senders are VDOs. Do yourself a favor and upgrade to Kavlicos for both of them.


Yep, I have the old style VDO sensors. Guess I'll be changing them. Thanks!
 
If I may, what would cause an actual rise in oil pressure during normal operation of an otherwise healthy engine?
 
Wrote about it in another post recently. I had the same or similar happen. If its the single pole sensor, they ground through the manifold it is screwed into which is grounded to the firewall and untimately shares a ground with your EFIS. This ground is unreliable. My EFIS manufacturer recommended brazing a ground wire to the sender case and grounding directly to the engine case. I followed this recommendation and it now works as it should.
Previously, I also had intermittent high oil pressure readings like yours. When it went to 130 psi, I started looking for a fix. That is when I read the article on my EFIS manufacturer's web page which seems to have solved my problem
 
Oil pressure is the one instrument which needs a mechanical backup. What would you have done if the error (assuming it is an indication error) had shown 20psi?
 
I have had a couple VDO pressure sensors go bad, giving erratic and high indications on my Dynon. Last replacement got an upgrade to a Kavlico sensor, no problems since.

Same here....with the old Van's supplied sensor, same goes for fuel pressure I found.
 
Oil pressure is the one instrument which needs a mechanical backup. What would you have done if the error (assuming it is an indication error) had shown 20psi?

So do mechanical sensors need a backup? They can fail, too. And I'm unaware of any certificated light aircraft (Cessna, Piper, etc.) which have a backup.

And if you have a backup, and it reads differently than the primary, you now have the problem of "taking two clocks to sea". Which one is right?

The answer to your question, of course, is to land and sort it out on the ground.
 
If I may, what would cause an actual rise in oil pressure during normal operation of an otherwise healthy engine?

A very high oil pressure can be just as dangerous as low oil pressure. I have had two engine failures, admittedly turbines, because there was a blockage in the oil return line. This resulted in a high oil pressure indication but temperature was normal because it was being read downstream of the blockage.

If you have faulty senders, change them. You don't want to do a precautionary landing and damage something, or yourself, because of an indication problem.
 
which is what I'd have done if it showed 20.

If the nearest airport is 50 miles away, would you take the risks involved in landing on a road? How about, in the case of two gauges, if one gauge still showed normal pressure, one showed 20? If one really believed the pressure was dropping towards zero, a precautionary landing on a road would be the proper course of action. However, if one gauge still showed pressure, and all other indications were normal, I'd fly on.
 
I have had a couple VDO pressure sensors go bad, giving erratic and high indications on my Dynon. Last replacement got an upgrade to a Kavlico sensor, no problems since.
What display and sensor do you have?

I had the exact same issue. With the old Dynon sensor, I would occasionally see high oil pressure on takeoff. But in the last few months it starting spiking in flight. Replaced with the new Kavlico (not exactly a drop in replacement), and oil pressure reading is back to normal.
 
Does the Kavlico output ohms like the VDO or is it a volts or amps output? The 3 wire configuration has me wondering and I cannot find any documentation.
 
Does the Kavlico output ohms like the VDO or is it a volts or amps output? The 3 wire configuration has me wondering and I cannot find any documentation.

Voltage is applied on 2 lines, and a signal voltage is measured on the 3rd line. I know in the case of the G3X, the signal is 5 volts. Not sure what range it can handle.
 
With the Kavlico sensors and the AFS 4500:
- Black wire gets a local or an EMS ground
- Green wire connects to the wire that used to go to the VDO sensor
- Red wire gets +5VDC from the AFS pin 19 on the 37-pin EMS connector
 
With the Kavlico sensors and the AFS 4500:
- Black wire gets a local or an EMS ground
- Green wire connects to the wire that used to go to the VDO sensor
- Red wire gets +5VDC from the AFS pin 19 on the 37-pin EMS connector

Jesse, so am I to take it that no other change is required to use the Kavlico senders wither the AFS 4500? Is the output the same, re. Ohms vs output voltage? I only see VDO and Stewart Warner options in the setup page.

Also, I already have 5 volts output from the EFIS in the engine compartment for the GPS antenna, can I just tap into that?

I have to do something about it now. The oil pressure sender had stopped causing trouble, but now both the oil AND fuel pressure units are wonky and I?ve grounded the airplane until I get it straightened out.

Also, what are the Kavlico part numbers?
 
So this is a timely thread for me as both my VDO fuel and oil pressure sensors have started acting flaky... and my oil sensor has already been replaced once. Question though, for a GRT 4000 EIS system, these Kavlico sensors don?t appear to be plug and play as I don?t have a 5V output under the hood. Any ideas on how to install these new sensors with GRT or am I stuck with the crappy VDOs?
 
I have an AFS 5400 and 3500 and have replaced the fuel pressure sensor twice and oil pressure sensor once. The changes resulted in fixes. I have the VDO sensors. Sounds like it might be time for an upgrade.
Ryan
 
Me too - oil pressure spikes

This forum is great! I have the same problem and it is getting more frequent. Oil pressure starts out ok, but then on run-up spikes up to 115 or so. That may be allowable for the first 10 minutes and I changed the alarm settings on my D180 accordingly. Then it would settle down at 85psi and all would be well.

Until it sometimes starts to climb again IN FLIGHT to over 115 and the alarms are all going off in my ears. Then settles back to 85 for a period of time before climbing again.

Until I read this blog I suspected the gauge because I could not think of any engine functionality that would cause this, but I am glad that others have had the same problem and determined that it is the pressure transducer.

I just ordered the Klavico sender from Dynon. I fully expect it to fix my problem.

Gordon R
 
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