Oil pressure relief valve, again: Low pressure high temps: Standoff

[willerjim273]

Hello all. Happy New Year.

My engine is a 1980 M20K  GB C LB with Black Magic and intercooler. I fly mainly out of the Denver area over the rocks to Grand Junction. 15.5 to 17.5k is typical. I usually run her at 65% and have kept the JDM alarms very conservative. No problems until my last annual. The shop is a reputable one, I believe, and they do not seem to get any more honest then Greg the owner. I departed BJC for EIK (20 miles) with barley enough time to put the gear down by the time tower let me go. I SHOULD have conducted a thorough flight test. I landed and put her away.  On the next flight, with an instructor friend, the EI-17 audio alert blared "check engine monitor". The oil temp alarm sounded exceeding the limit of 200. I know that is low, but let's not get into that right now. Point is that high oil temps has never been an issue. The oil pressure was down at the bottom of the green and we were at 8000 ft. Marginal at best but certainly not right. And for sure not going over the mtns. 

I just reviewed the past postings on TSIO 360's and this issue. The most appropriate is from March of 2015 when Don had the same problem. Will,  Doc and Don figured it had to be a piece of crud in the relief valve (RV) port. I popped the cowl and located it. I read how Don, and his short mechanic, had to make a jig and decided that picture did not look great. I had also just had the plane annualed. If I messed with it and it went south, guess what? So I took her back about a week later with no more than an hour TT since they worked on it. We went on a 3 week vacation out of town. I approved the shop owner to fly the plane. He said he had mucho, mucho time in the 231, owned 50+ airplanes etc. etc., and was very familiar with the need to NOT over boost. I had just installed a vernier throttle for that reason. My 231 has always been EXTREMELY sensitive to over boost. And I have been pretty fanatical about that issue to the point that I had a digital manifold pressure Brand: Aerospace Logic M210 with fuel flow installed 2 yrs ago. I explained to him that the throttle was VERY sensitive and to just use the vernier for takeoff. 

Back to the point. While out of town we talked. He said he had to abort the takeoff because "things did not look right." He said he over boosted and had never experienced anything like that sensitivity before. 

So, 2 oil change later, no metal in the oil. We changed oil filter twice now and no metal. Bottom line is it has been 2 months in his shop and he does not seem to be motivated to figure it out. I have told him quote clearly that regardless of the cause, I am not placing blame anywhere and I am happy to pay to get it fixed. Just get it done. I am a paying customer and do not expect any favors. I am of the position that since he has been keeping her hangered at BJC at his expense, I prefer he do it and not take it away for obvious reasons.

We may need a psyc to figure this one out.

I have seen dozens of planes in and out in the meantime. It sounds like he does own a fleet of flight school planes and demand is stupid. So a Mexican......."south American" standoff. I stopped by today and the plane is still sitting there taking up valuable space. He first started talking about the sensitivity of the throttle saying that he needs to check the oil lines going to the turbo.. He has heard that if they are reversed, that can cause the sensitivity  problem. Like I was there to talk about that? I have flown that plane for close to 5 years now and have always just been super careful. Never made any metal and have great compressions. How di that come up? I said fine, but what about the problems I brought the plane to get fixed in the first place?

He had finally adjusted the pressure valve and thinks he can get the plane back to me tomorrow, 3 Jan. I said hold on!  Have you tested to verify all is well? No. 

My engine is like Don's. There is no adjustment on that block. I told him that that RV does not have an adjustment. He said he put a "washer" in there. 

I have hired Mike Busch's outfit. About $600 by the way. But the shop does not want to "work with them" were the words of the rep of Mike's on this case. Mike's policy it appears is they cannot do much if the mechanic will not take guidance. 

What would you do? 
I obviously need to get a oil analysis or at least see the filter before I accept the AC. No desire right now to go in there guns blazing and have her pushed out of the hangar. 

Could he have really have screwed something serious up? Kind of doubt it, but what if? Can you mess up an engine with a quick 40 or higher MP? (I have seen 40MP before with plenty of throttle to go, but the pop off always gets your attention, if you have any feeling for the machine.  Being an experienced airplane guy it is doubtful he would not immediately pull power. Is he afraid of something or just super busy?

To describe the sensitivity I assume is inherent is thus: On takeoff, max brakes, at 30 inches release brakes, twist in about a # 2 pencil lead amount more and I am at 36-38. If a # 2 pencil total width is added, you are at 40. Sensitive. You other K guys. Is that about right?

 

Thanks guys. 

 

 

[willerjim273]

Clarification on my post. about oil pressure problem on M20K Just read post Oil pressure relief valve, again: Low pressure high temps: Standoff again.

 

 

To clarify, this needs to be added: I approved the shop owner to test fly the plane to confirm himself the problems and see the low pressures and high temps

[N231BN]

Was it very cold out on your last flight? A congealed oil cooler will cause low OP and high OT.

Do you have a Merlyn or stock wastegate?

[willerjim273]

No,

 

The weather was warm. He last flew her in mid to late September. 

 

 

[willerjim273]

And the waste gate is a Merlyn. Tks

[A64Pilot]

This suddenly came about right?

A run up with cool oil will show you relief valve pressure setting, it will stop climbing at set point, now this thing is a spring so cracking pressure will be lower than full open pressure, but if you get 100 PSI on cool oil, but say only 65 or so in cruise, it’s not the relief valve adjustment.

I think the only way you’re going to be able to rule out the relief valve is to pull it and inspect the seat on the engine and relief valve for damage and or something preventing closing.

Ref cold oil in a cooler, the oil vernatherm doesn’t work like you would think, we think the cooler is bypassed until the vernatherm opens then oil flows through it, but that’s not how it works, what it does is with cold oil the oil flow is through the cooler and bypassed meaning the cooler warms with the engine, then as it gets hot the vernatherm closes off the bypass, but there is oil flow through the cooler at all times, that’s why in real cold weather you may have to cover some of the cooler.

[DonMuncy]

1 hour ago, A64Pilot said:

, what it does is with cold oil the oil flow is through the cooler and bypassed meaning the cooler warms with the engine, then as it gets hot the vernatherm closes off the bypass, but there is oil flow through the cooler at all times, that’s why in real cold weather you may have to cover some of the cooler.

I'm not sure I understand that. Can you say it another way.

[A64Pilot]

51 minutes ago, DonMuncy said:

I'm not sure I understand that. Can you say it another way.

OK the vernatherm is in the oil bypass passage, when cold it’s open so oil flows through the bypass AND the cooler, as the oil heats up, the vernatherm begins closing forcing more and more of the oil through the cooler.

But no matter how cold it is, there is some oil flow through the cooler, this means all the oil in the engine is warmed at the same time and oil flow is NOT blocked.  There is no trapped cold congealed oil, but it also means the cooler is cooling oil, so in real cold temps it’s normal to have to block airflow through the cooler or the oil never warms up much.

It’s just the opposite to an automobiles radiator, there the thermostat blocks off the water flow through the radiator usually allowing a small amount around a bypass, a small amount, a fraction of full flow, but water had to circulate some or the thermostat wouldn’t experience warm water to begin opening it up.

The difference is in a cars radiator you can block flow, but if you blocked flow in an engines oil system you can imagine the result.

Also thermostats tend to fail closed as closed is it’s relaxed position, and a vernatherm tends to fail open as it’s its relaxed position. 

Lycoming the way they word it has caused confusion, they word it saying when the vernatherm is open it allows oil to bypass the cooler, which it does, but the way they word it seems to indicate all oil bypasses the cooler which doesn’t happen, if it did then blocking airflow through the cooler wouldn’t raise oil temp up close to normal in real cold weather.

Decent article explaining it

https://cessnaowner.org/vernatherm-wear-what-are-your-replacement-options/

On edit I believe a failed vernatherm is rare, but a failed one can lead to high oil temps if it fails open because it’s not blocking oil flow to bypass the cooler, given a choice of two flow paths a fluid will take the path of least resistance and that’s likely to be the bypass. 

[DonMuncy]

Thanks for the explanation.

[GeeBee]

Get out of that shop any way you can and never come back. They do not know what they are doing. The clue is not the over boost (which is bad enough) but the refusal to take advice. That means they don't know what they are doing or how to talk about it.

[kortopates]

An ultra sensitive throttle on a Merlin is almost always a sign that it needs to be rebuilt by Merlin. It’s neither very expensive or time consuming.

There are a lot of things to consider with high oil temp and low pressure starting with where your oil temp probe is located or accuracy of the gauges. If it not an approved for primary monitor, the probe isn’t even at the official measuring position but up in front where OT is warmest. Plus 200F is not hot; especially in climb with low IAS.


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[hubcap]

15 hours ago, GeeBee said:

Get out of that shop any way you can and never come back. They do not know what they are doing. The clue is not the over boost (which is bad enough) but the refusal to take advice. That means they don't know what they are doing or how to talk about it.

^^^^This.^^^^

 

[Raymond J1]

Have you had the opening pressure of the bypass located in the oil filter adapter checked ?
I am not talking about the bypass of the oil filter in a screw-on cartridge, but about the one located in the adapter, near the vernatherm.

[N201MKTurbo]

4 minutes ago, Raymond J1 said:

Have you had the opening pressure of the bypass located in the oil filter adapter checked ?
I am not talking about the bypass of the oil filter in a screw-on cartridge, but about the one located in the adapter, near the vernatherm.

Doesn't that bypass just bypass the oil filter? I can't see how it would affect the oil pressure.

[N201MKTurbo]

I like @kortopates suggestion about the throttle. Except I would remove the Merlyn and try to clean it first, it may just be full of deposits and stuck.

[Raymond J1]

1 hour ago, N201MKTurbo said:

Doesn't that bypass just bypass the oil filter? I can't see how it would affect the oil pressure.

The route of the oil in order...

1) Pump,
2) Heat exchanger if necessary... Vernatherm decide,
3) Temperature probe,
4) Oil filter (bypass in the filter if clogged),
5) Optionally a second bypass if the filter is clogged (12 to 14 psi),
5) Pressure sensor,
6) Adjustable pressure regulator.

As it was said before, when the oil is cold, the vernatherm is open and the oil does not pass through the radiator...
When the oil is hot, the vernatherm closes and the oil flows through the cooled radiator.

The température of the oil is controlled before filtration...

If the température sensor is right and the oil température is too hot, it"s nécessary to check the clogging of the oil radiator.
If the température sensor is right and the oil température is too cold, it's necéssary to check the vernatherm.

The oil pressure is checked after filtration and before the pressure regulator.
The pressure regulator is adjustable and its adjustment is done with a new and unclogged filter, that is to say with closed bypasses.
If the bypass in the filter or if the one in the adapter is defective, there is no filtration... But there is also no correct calibration of the pressure regulator.

However, a bad adjustment of the pressure regulator, because of a defective bypass, can lead to a lower hot oil pressure, that is to say with a higher flow rate in the radiator, for the same opening value of the vernatherm.
As you say you have changed the oil filter several times... So its built-in bypass, you just have to check the bypass located in the oil filter adapter.

Edited January 5, 2023 by Raymond J1

[Guest]

2 hours ago, Raymond J1 said:

Have you had the opening pressure of the bypass located in the oil filter adapter checked ?
I am not talking about the bypass of the oil filter in a screw-on cartridge, but about the one located in the adapter, near the vernatherm.

All good for a Lycoming, but the OP has a Continental engine.

[N201MKTurbo]

1 hour ago, Raymond J1 said:

The route of the oil in order...

1) Pump,
2) Heat exchanger if necessary... Vernatherm decide,
3) Temperature probe,
4) Oil filter (bypass in the filter if clogged),
5) Optionally a second bypass if the filter is clogged (12 to 14 psi),
5) Pressure sensor,
6) Adjustable pressure regulator.

As it was said before, when the oil is cold, the vernatherm is open and the oil does not pass through the radiator...
When the oil is hot, the vernatherm closes and the oil flows through the cooled radiator.

The température of the oil is controlled before filtration...

If the température sensor is right and the oil température is too hot, it"s nécessary to check the clogging of the oil radiator.
If the température sensor is right and the oil température is too cold, it's necéssary to check the vernatherm.

The oil pressure is checked after filtration and before the pressure regulator.
The pressure regulator is adjustable and its adjustment is done with a new and unclogged filter, that is to say with closed bypasses.
If the bypass in the filter or if the one in the adapter is defective, there is no filtration... But there is also no correct calibration of the pressure regulator.

However, a bad adjustment of the pressure regulator, because of a defective bypass, can lead to a lower hot oil pressure, that is to say with a higher flow rate in the radiator, for the same opening value of the vernatherm.
As you say you have changed the oil filter several times... So its built-in bypass, you just have to check the bypass located in the oil filter adapter.

Still don’t see how the oil filter bypass will affect the oil pressure. And I’m very familiar with the Lycoming oil system.

[EricJ]

Here's the Continental-style oil pump, filter, and relief valve assembly:

[Raymond J1]

1 hour ago, N201MKTurbo said:

Still don’t see how the oil filter bypass will affect the oil pressure. And I’m very familiar with the Lycoming oil system.

So you remember the old AC sieve, which did not have a vernatherm but a viscosity valve and an obligatory passage of the oil via the radiator once the correct viscosity was reached (viscosity valve closed).
And how much the pressure varied depending on the viscosity (hot or cold oil), so the flow rate in the radiator.

The new filter adapter is still sensitive to this problem, even if the vernatherm valve reduces its magnitude and even if it is not the bypass of the oil filter that modifies the pressure.

As before, a leaky bypass can generate a bad calibration of the regulator, so not the right pressure setting. The pressure regulation will still be done, but not at the right value.
And the viscosity of the oil can always change the flow rate in the cooler, so change the pressure/back pressure on the vernatherm valve... The thick (cold) oil pushes more towards the opening of the vernatherm than the fluid (hot) oil... Which is fine, unless you change the monograde oil to a multigrade oil, because then you have to change the cold pressure values if you want to keep the same flow rate as in monograde... Or make hot oil settings

It is this case that leads some owners of "experimental" to replace the vernatherm with a viscosity valve (like the old system) and to mount a ball valve on the exchanger piping to manually control the oil temperature (but that's another topic).

Lycoming and continental operate with the similar oil circuit organization.
 

[N201MKTurbo]

7 minutes ago, Raymond J1 said:

So you remember the old AC sieve, which did not have a vernatherm but a viscosity valve and an obligatory passage of the oil via the radiator once the correct viscosity was reached (viscosity valve closed).
And how much the pressure varied depending on the viscosity (hot or cold oil), so the flow rate in the radiator.

The new filter adapter is still sensitive to this problem, even if the vernatherm valve reduces its magnitude and even if it is not the bypass of the oil filter that modifies the pressure.

As before, a leaky bypass can generate a bad calibration of the regulator, so not the right pressure setting. The pressure regulation will still be done, but not at the right value.
And the viscosity of the oil can always change the flow rate in the cooler, so change the pressure/back pressure on the vernatherm valve... The thick (cold) oil pushes more towards the opening of the vernatherm than the fluid (hot) oil... Which is fine, unless you change the monograde oil to a multigrade oil, because then you have to change the cold pressure values if you want to keep the same flow rate as in monograde... Or make hot oil settings

It is this case that leads some owners of "experimental" to replace the vernatherm with a viscosity valve (like the old system) and to mount a ball valve on the exchanger piping to manually control the oil temperature (but that's another topic).

Lycoming and continental operate with the similar oil circuit organization.
 

But the pressure regulator is downstream of the filter and the bypass. As long as the pressure upstream of the regulator is in excess of of the regulated pressure, the output of the regulator should be the regulated pressure, which is set by the spring pressure on the ball. I agree that the viscosity of the oil has an effect on the regulated pressure, but bypassing the filter shouldn't have a significant effect on the oil temperature and thus the viscosity.

[Pinecone]

Jumping onto this thread.

What I am seeing is low oil temp and low pressure.

TSIO-360-SB.

Both stock gauges and JPI 830 (not primary) installed.  I understand that the JPI numbers will be different due to different sensor locations.

But on a recent trip, the analog oil pressure seemed to be 60 - 65 psi (hard to say with minimal markings).  JPI reads 52 - 54 psi.

Oil temp- analog is very low.  Maybe 1/4 of the way up the green arc, so maybe 140.  JPI reads 166.

Just out of annual, and they adjusted the oil pressure relief up some.

What say the experts? 

[Raymond J1]

1 hour ago, N201MKTurbo said:

But the pressure regulator is downstream of the filter and the bypass. As long as the pressure upstream of the regulator is in excess of of the regulated pressure, the output of the regulator should be the regulated pressure, which is set by the spring pressure on the ball. I agree that the viscosity of the oil has an effect on the regulated pressure, but bypassing the filter shouldn't have a significant effect on the oil temperature and thus the viscosity.

On Lycoming, yes the regulator is downstream of the filter, the cooler and the pressure switch too.
The pressure you are measuring is that upstream of the regulator, yes it is indeed slightly higher than the regulated pressure... Finally, if the flow rate of the pump is sufficient.

The differences in viscosity cause the upstream pressure to fluctuate... So the regulated pressure.

The viscosity varie with the grade, but also the température of the oil. However, this température depends on the flow rate through the radiator, the level of clogging of the filter / bypass passage section, the sampling made by the propeller governor who has his own pump.
These problems are also at the origin to the creation of the new filter adapter, with integrated vernatherm and bypass, which corrects the major problem of the original AC sieve, but without completely erasing it.

That is why it is essential to carefully check all the functions included in the cartridge filter adapter before proceeding with the adjustment or modification of the pressure setting.
As it's important to carefully review the pressure / flow adequacy if you change the type of oil (monograde to multigrade or vice versa).

Preferably, check and tare the oil pressure regulator for a hot engine, maximum speed (full small step is the maximum request of the governor), with an old filter (partly clogged) and a vernatherm valve at the correct adjustment rating and seat in good condition... The bad conditions that degrade the pressure upstream of the regulator.
When cold, just check that you are above the imposed minimum threshold.

Edited January 5, 2023 by Raymond J1

[Will.iam]

3 hours ago, Pinecone said:

Jumping onto this thread.

What I am seeing is low oil temp and low pressure.

TSIO-360-SB.

Both stock gauges and JPI 830 (not primary) installed.  I understand that the JPI numbers will be different due to different sensor locations.

But on a recent trip, the analog oil pressure seemed to be 60 - 65 psi (hard to say with minimal markings).  JPI reads 52 - 54 psi.

Oil temp- analog is very low.  Maybe 1/4 of the way up the green arc, so maybe 140.  JPI reads 166.

Just out of annual, and they adjusted the oil pressure relief up some.

What say the experts? 

My pressure is around 60-65 psi on an MB engine. Oil temp is vertical on the analog so guessing 180? If you do some slow flight at 22” with cowl flaps closed you can get the oil temp up as well as CHT’s when it’s cold outside due to inefficient airflow through the cowling. Maybe warm up the oil some to see where the pressure goes?

[Pinecone]

Good idea