oil pressure drop

[toomany]

any bravo flyers ever have their oil pressure drop significantly then come back up?

i was climbing out in imc on thursday morning and at 5700' i noticed the oil pressure guate was indicating 20-30psi, right on the red line. i immediately pulled power (climb power was 34/24). i reduced to approx 25 inches and made my turn back to the airport.   oil temp stayed where it always does at 180° so i didn't think i was losing oil. there was no engine roughness or any abnormalities apart from the low press indication. as i descended down to 2500' the oil pressure started reading higher - slowly, not all of a sudden. by the time i was vectored onto final the press was back to 80 psi.

i first looked at the pressure transducer to see if there were any signs of failure/leaks - nothing.  i removed the oil line from the t to the transducer on the accessory housing and blew out the oil in the line onto a paper towel to see if there were and contaminants - nothing. i cleaned the inside of the transducer with a twisted paper towel and found nothing.  i did notice the transducer in the svc manual shows the unit vertical. mine was horizontal so i changed to mounting vertical. 

after that i checked the gauge w the mooney rheostat that plugs into the 4 prong connector at the fire wall- the gauge read within 2.5 psi of the instrument settings. 

i pulled the gauge and installed another one and got more accurate readings off the spare gauge. i'm thinking 2.5 psi difference isn't horrible, so put the factory gauge back in  

i then ground ran it and noticed rpm wouldn't hold below 33 inches   i could hold 34/24 but as soon as i reduced to cruise of 28.5 the prop would fall off to 21-2200 rpm  with veneer knob the whole way in. 

i cranked the oil pressure relief screw in one turn and noticed better oil pressure at low idle and cruise settings but rpm still wouldn't hold at less than 33 inches  probably due to lack of resistance 

i pulled the prop gov to check the screen and found the engine was put together w/o screened gasket   - one will be installed next week - but found nothing out of sorts  

i then flew to 10,000' around the airport and noticed no drop in oil pressure and the prop held rpm wherever i put it   i experimented w high man pressure/low rpm  high rpm/low mp etc etc  - did super steep climbs to near vertical to see if i could get any cavitation at the pick up - and nothing, oil pressure remained constant the whole time at 70 psi  i them landed and changed the oil and strained it through a shop rag and found no metal or anything weird  

i'm thinking the transducer may be on its way out - the oil press and fuel press gauges both kind of give s slight waver in cruise sometimes .  they were doing this on the flight at the airport to 10,000'  .  it's not a large movement, more like a shimmy back and forth, and i know it'd be impossible for the oil press to fluctuate at constant rpm unless a relief valve has dirt in it holding it open, but even then i think it'd be more of a drop in press not a fluctauation   my concern is the low press reading i experienced  

if anyone is familiar w similar experiences please let me know what the remedy was - id try new transducers  but they're no longer produced and out of stock everywhere i've looked   

probably going to install a second oil and fuel press gauge - any recommendations would be greatly appreciated  

engine has less than 100 hrs since oh 

[jetdriven]

You sound like a very thorough troubleshooter, and it seems like your oil pressure transducer is the issue. Do you have a JPI that shows oil  pressure as well? That is something You can cross reference.

[LANCECASPER]

7 hours ago, toomany said:

any bravo flyers ever have their oil pressure drop significantly then come back up?

i was climbing out in imc on thursday morning and at 5700' i noticed the oil pressure guate was indicating 20-30psi, right on the red line. i immediately pulled power (climb power was 34/24). i reduced to approx 25 inches and made my turn back to the airport.   oil temp stayed where it always does at 180° so i didn't think i was losing oil. there was no engine roughness or any abnormalities apart from the low press indication. as i descended down to 2500' the oil pressure started reading higher - slowly, not all of a sudden. by the time i was vectored onto final the press was back to 80 psi.

i first looked at the pressure transducer to see if there were any signs of failure/leaks - nothing.  i removed the oil line from the t to the transducer on the accessory housing and blew out the oil in the line onto a paper towel to see if there were and contaminants - nothing. i cleaned the inside of the transducer with a twisted paper towel and found nothing.  i did notice the transducer in the svc manual shows the unit vertical. mine was horizontal so i changed to mounting vertical. 

after that i checked the gauge w the mooney rheostat that plugs into the 4 prong connector at the fire wall- the gauge read within 2.5 psi of the instrument settings. 

i pulled the gauge and installed another one and got more accurate readings off the spare gauge. i'm thinking 2.5 psi difference isn't horrible, so put the factory gauge back in  

i then ground ran it and noticed rpm wouldn't hold below 33 inches   i could hold 34/24 but as soon as i reduced to cruise of 28.5 the prop would fall off to 21-2200 rpm  with veneer knob the whole way in. 

i cranked the oil pressure relief screw in one turn and noticed better oil pressure at low idle and cruise settings but rpm still wouldn't hold at less than 33 inches  probably due to lack of resistance 

i pulled the prop gov to check the screen and found the engine was put together w/o screened gasket   - one will be installed next week - but found nothing out of sorts  

i then flew to 10,000' around the airport and noticed no drop in oil pressure and the prop held rpm wherever i put it   i experimented w high man pressure/low rpm  high rpm/low mp etc etc  - did super steep climbs to near vertical to see if i could get any cavitation at the pick up - and nothing, oil pressure remained constant the whole time at 70 psi  i them landed and changed the oil and strained it through a shop rag and found no metal or anything weird  

i'm thinking the transducer may be on its way out - the oil press and fuel press gauges both kind of give s slight waver in cruise sometimes .  they were doing this on the flight at the airport to 10,000'  .  it's not a large movement, more like a shimmy back and forth, and i know it'd be impossible for the oil press to fluctuate at constant rpm unless a relief valve has dirt in it holding it open, but even then i think it'd be more of a drop in press not a fluctauation   my concern is the low press reading i experienced  

if anyone is familiar w similar experiences please let me know what the remedy was - id try new transducers  but they're no longer produced and out of stock everywhere i've looked   

probably going to install a second oil and fuel press gauge - any recommendations would be greatly appreciated  

engine has less than 100 hrs since oh 

What year is your Mooney? What gauges do you have? The Moritz gauges (troublesome)? A picture of your panel would be helpful.

[toomany]

it's and '89 version and it has the jpi700? that doesn't have any oil press indication. i'm told the gauges are not moritz and according to the svc man the transducer is a kulite apt 201.  

[toomany]

i just read some posts regarding the fuel press transducers for the bravo and the proposed remedy(s). they mention cleaning up the wires/sockets on the transducer connections and/or installing a new cpnnector. i'll try doing some clean up of the connection  and if that fails i'll re-wire it vía new connectors. 

this forum is a great resource!

[carusoam]

The Kulite sensor gets a fair amount of press… they don’t last forever, and are hard to find…

It has a small vent hole to be familiar with as well…

PP thoughts only,

-a-

[LANCECASPER]

13 hours ago, toomany said:

it's and '89 version and it has the jpi700? that doesn't have any oil press indication. i'm told the gauges are not moritz and according to the svc man the transducer is a kulite apt 201.  

Most likely you still have your SigmaTek gauges then, which is good news since those gauges (cube-shaped) can be replaced individually. I have an Oil Pressure gauge from a '93 Bravo that I sold last year that has less than 100 hours on it. I had a similar thing happen after we did a top overhaul (Bravo conversion) - no oil pressure First thought was that the Kulite transducer was bad, but that turned out fine, my old gauge was bad. Jimmy Garrison just happened to have a brand new one in the box that I bought. If you need it send me a PM.

 

[rbp]

if you need SigmaTek gauges, I have a full set from my '98

[affricate]

On 10/15/2022 at 7:13 PM, toomany said:

any bravo flyers ever have their oil pressure drop significantly then come back up?

i was climbing out in imc on thursday morning and at 5700' i noticed the oil pressure guate was indicating 20-30psi, right on the red line. i immediately pulled power (climb power was 34/24). i reduced to approx 25 inches and made my turn back to the airport.   oil temp stayed where it always does at 180° so i didn't think i was losing oil. there was no engine roughness or any abnormalities apart from the low press indication. as i descended down to 2500' the oil pressure started reading higher - slowly, not all of a sudden. by the time i was vectored onto final the press was back to 80 psi.

i first looked at the pressure transducer to see if there were any signs of failure/leaks - nothing.  i removed the oil line from the t to the transducer on the accessory housing and blew out the oil in the line onto a paper towel to see if there were and contaminants - nothing. i cleaned the inside of the transducer with a twisted paper towel and found nothing.  i did notice the transducer in the svc manual shows the unit vertical. mine was horizontal so i changed to mounting vertical. 

after that i checked the gauge w the mooney rheostat that plugs into the 4 prong connector at the fire wall- the gauge read within 2.5 psi of the instrument settings. 

i pulled the gauge and installed another one and got more accurate readings off the spare gauge. i'm thinking 2.5 psi difference isn't horrible, so put the factory gauge back in  

i then ground ran it and noticed rpm wouldn't hold below 33 inches   i could hold 34/24 but as soon as i reduced to cruise of 28.5 the prop would fall off to 21-2200 rpm  with veneer knob the whole way in. 

i cranked the oil pressure relief screw in one turn and noticed better oil pressure at low idle and cruise settings but rpm still wouldn't hold at less than 33 inches  probably due to lack of resistance 

i pulled the prop gov to check the screen and found the engine was put together w/o screened gasket   - one will be installed next week - but found nothing out of sorts  

i then flew to 10,000' around the airport and noticed no drop in oil pressure and the prop held rpm wherever i put it   i experimented w high man pressure/low rpm  high rpm/low mp etc etc  - did super steep climbs to near vertical to see if i could get any cavitation at the pick up - and nothing, oil pressure remained constant the whole time at 70 psi  i them landed and changed the oil and strained it through a shop rag and found no metal or anything weird  

i'm thinking the transducer may be on its way out - the oil press and fuel press gauges both kind of give s slight waver in cruise sometimes .  they were doing this on the flight at the airport to 10,000'  .  it's not a large movement, more like a shimmy back and forth, and i know it'd be impossible for the oil press to fluctuate at constant rpm unless a relief valve has dirt in it holding it open, but even then i think it'd be more of a drop in press not a fluctauation   my concern is the low press reading i experienced  

if anyone is familiar w similar experiences please let me know what the remedy was - id try new transducers  but they're no longer produced and out of stock everywhere i've looked   

probably going to install a second oil and fuel press gauge - any recommendations would be greatly appreciated  

engine has less than 100 hrs since oh 

I have a 1989 Bravo with Sigma Tek  gauges. Happened to me 3x since MOH, once immediately after oil change. The 3x it happened was within the first 20 min or so on short flights less than a hour. My JPI also doesn't have oil pressure so I can't cross reference. I tap the Sigma Tech and it comes right all 3 times. 

I constantly check my oil, and change it every 25 hrs. Never happens on multiple cross country flights 6-7 hrs. 29MP 22 RPM is my sweet spot.

 

Plan is upgrade engine monitor and panel soon.

[toomany]

On 1/29/2023 at 5:27 PM, affricate said:

I have a 1989 Bravo with Sigma Tek  gauges. Happened to me 3x since MOH, once immediately after oil change. The 3x it happened was within the first 20 min or so on short flights less than a hour. My JPI also doesn't have oil pressure so I can't cross reference. I tap the Sigma Tech and it comes right all 3 times. 

I constantly check my oil, and change it every 25 hrs. Never happens on multiple cross country flights 6-7 hrs. 29MP 22 RPM is my sweet spot.

 

Plan is upgrade engine monitor and panel soon.

hasn't happened to me since but i went ahead and had a 28v auto style gauge installed to. monitor the pressure until we upgrade to a newer JPI. I have noticed that the fuel press and oil press both "shake" intermittently in concert with one another. not sure if this is a voltage issue but i believe they both use the same type of transducer.