231 oil pressure

[peevee]

LB engine.

 

For awhile we've had low oil pressure when the oil is hot, especially at idle. Today it was on the bottom peg at idle after a flight.

We run aeroshell 100. The adjustment is up about as far as it can go on the relief spring/housing. We have replaced the spring and had the housing/orifice cleaned. At start up it goes to the top of the green and then decreases as it warms. At cruise power it's maybe 1/3rd into the green. We only have the original indicator, no digital, our EI doesn't do that or isn't hooked up.

 

Any ideas? Mechanic doesn't think he can hook up an external gauge to test it, said there's no transducer to worry about failing as it's just a line to the indicator itself. I think we're at a dead end and just operationally don't idle below 1k rpm when warm to keep the pressure up or operate as normal and assume the indication is just off on the 10 cent gauge and hope for the best.

[N5756v]

I don't have ideas but I would replace the gauge ,line and fitting just for peace of mind .

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[DonMuncy]

Be aware that on Continentals, the oil pressure pick up is downstream of all the bearings, etc., so virtually an pressure is enough at idle. As compared to Lycomings where the sensor is just after the oil pump.

However, the "seat" where the relief valve seats is subject to some imperfections, which will allow the pressure to be a little low at low speeds. Often, the imperfection is so slight that you won't notice at higher RPMs. There is a cutting tool which can be inserted to grind the seat down smooth and allows the pressure to build up higher before the relief valve allows the oil to "bypass".

I am not an A&P, but have been through this, and I think this info is generally correct.

[Guest]

7 hours ago, peevee said:

LB engine.

 

For awhile we've had low oil pressure when the oil is hot, especially at idle. Today it was on the bottom peg at idle after a flight.

We run aeroshell 100. The adjustment is up about as far as it can go on the relief spring/housing. We have replaced the spring and had the housing/orifice cleaned. At start up it goes to the top of the green and then decreases as it warms. At cruise power it's maybe 1/3rd into the green. We only have the original indicator, no digital, our EI doesn't do that or isn't hooked up.

 

Any ideas? Mechanic doesn't think he can hook up an external gauge to test it, said there's no transducer to worry about failing as it's just a line to the indicator itself. I think we're at a dead end and just operationally don't idle below 1k rpm when warm to keep the pressure up or operate as normal and assume the indication is just off on the 10 cent gauge and hope for the best.

Your mechanic should easily be able to install a "Tee" in the existing oil line and a hose and test gauge to confirm the existing airframe gauge.  You need to know the pressure is actually low before doing anything or worrying about it.

Clarence

7 hours ago, peevee said:

LB engine.

 

For awhile we've had low oil pressure when the oil is hot, especially at idle. Today it was on the bottom peg at idle after a flight.

We run aeroshell 100. The adjustment is up about as far as it can go on the relief spring/housing. We have replaced the spring and had the housing/orifice cleaned. At start up it goes to the top of the green and then decreases as it warms. At cruise power it's maybe 1/3rd into the green. We only have the original indicator, no digital, our EI doesn't do that or isn't hooked up.

 

Any ideas? Mechanic doesn't think he can hook up an external gauge to test it, said there's no transducer to worry about failing as it's just a line to the indicator itself. I think we're at a dead end and just operationally don't idle below 1k rpm when warm to keep the pressure up or operate as normal and assume the indication is just off on the 10 cent gauge and hope for the best.

 

[Zwaustin]

I too have an LB, run Aeroshell100 and had the same issue. My mechanic added a washer to the spring. Washer helped a bit at low idle. 

[peevee]

2 hours ago, DonMuncy said:

Be aware that on Continentals, the oil pressure pick up is downstream of all the bearings, etc., so virtually an pressure is enough at idle. As compared to Lycomings where the sensor is just after the oil pump.

However, the "seat" where the relief valve seats is subject to some imperfections, which will allow the pressure to be a little low at low speeds. Often, the imperfection is so slight that you won't notice at higher RPMs. There is a cutting tool which can be inserted to grind the seat down smooth and allows the pressure to build up higher before the relief valve allows the oil to "bypass".

I am not an A&P, but have been through this, and I think this info is generally correct.

Thanks, I remember reading your writeup on the issue and that is what prompted me to have the spring replaced and the housing cleaned out and checked. 

Plane is going to maxwell in a couple weeks for something else, I'll see if he can clean that orifice