High oil pressure outside of idle

[par]

I have been seeing oil pressure above the high end red line for a while now when I run up the ingine for takeoff. In cruise I am barely below high red line as shown in the picture below. I'm having my IA look at it but how big of a concern is this in reality?

[carusoam]

I believe that is adjustable via a spring/regulator?

Too much pressure can be bad for seals, making it a want to get fixed soon.

Easy enough to check with your mechanic.

Cold oil is more viscous and will generate higher pressure readings.  Selecting a different oil type may help.  Covering a portion of the oil cover may be a solution...

As usual, I am a PP, not a Mechanic.

Best regards,

-a-

[Andy95W]

This as actually discussed in a different thread about 1-2 years ago.  A search could find the results.

To recap:. at some point, Lycoming realized that higher oil pressure (within reason, of course) was better for getting oil to the cylinder heads, so they increased the oil pressure limitations on the Type Certificate Data Sheet (TCDS) to 95 psi.  The red line on our gauges, however, is still the old standard of about 85 psi.  Attached is a copy of the page from the TCDS to show your mechanic.

When your engine got overhauled, the overhauler did the right thing and set the oil pressure to the new and improved limits.  Be glad that you'll see slightly lower CHTs and have a slightly lower likelihood of valve sticking.

 

[ArtVandelay]

Just be sure the gauge is accurate before you start spending any money fixing a non problem.

[jetdriven]

Mine runs 95 PSI in cruise and exceeds 100 for a few minutes after takeoff.  The only thing that can blow out seals is crancase pressure.  What the higher oil pressure does do is get more oil onto the valve stems, a good thing.  

The newer 172s have an upper limit of something like 125 PSI of measured at the oil pump like ours do.  

[jamesm]

I had just done a oil change (Aug 2015 ) when I noticed High oil press pressure , oh what I thought it was too high, I backed out the engine press adjustment (5 year old engine overhaul) it was pretty much at the end of travel and saw hardly noticeable change.  After reviewing my engine data over the last 5 years (when I  installed engine monitor)  the oil pressure had been pretty consistent and   after talking to my person that did my engine overhaul  about oil pressure being too high.  Like others pointed out 95 psi max  and one may ask when was the oil pressure gauge  last calibrated?  When was the last  engine  overhaul and/or major engine work done?

 If I may point out,  if you look the oil pressure gauge needle width in comparison to  the  narrow range on the scale you are trying to read  to a finite resolution, I my humble option  I don't think you could  read  down to maybe 5 degrees at best for the particular range you are interested in and if you add  parallax to your reading it throws bunch error into the reading.

In my case the problem was me.  My conclusion was that I probably I didn't noticed engine oil pressure as being high or as high as I thought it ought to be from the many oil  changes that I have done over the years but I verified with my data from the engine monitor and conferred  with others IA 's and engine shop that overhauled the engine.  No more worries.

I hope this helps.

James '67C

Edited February 2, 2016 by jamesm

[Guitarmaster]

I have the same problem. The good news is, it's not really a problem. Before you do anything put a manual oil pressure gauge on it. My oil pressure gauge in the cockpit is 20 psi high.

I thought I had excessively high oil pressure, it turns out that I was holding normal oil pressure and I'm really glad I didn't do anything to reduce it!

Sent from my XT1254 using Tapatalk

[Marauder]

I have the same problem. The good news is, it's not really a problem. Before you do anything put a manual oil pressure gauge on it. My oil pressure gauge in the cockpit is 20 psi high.

I thought I had excessively high oil pressure, it turns out that I was holding normal oil pressure and I'm really glad I didn't do anything to reduce it!

Sent from my XT1254 using Tapatalk

Here is what mine looks like in cruise on 53° day, full throttle, 2500 RPM.

Sent from my iPad using Tapatalk

[M20F]

18 hours ago, teejayevans said:

Just be sure the gauge is accurate before you start spending any money fixing a non problem.

I would second this, also may want to check out why your CHT's are so high.

[par]

I'm having the IA check the oil pressure manually to check the gauge. 

As for the CHT'S, I do not trust that gauge because I sometimes have to flick at it to get it to work. I think I may need to OH that gauge cluster or just put that money towards an engine monitor.

[par]

I went for a quick flight today and paid close attention to my CHT's this time after M20F mentioned it. While I don't trust the gauge completely, here is what I saw today.

-CHT's were close to redline while IDLING to warm up the engine @ 1000RPM, even after I opened the cowl flaps. OAT was mid 40's.

-On climb out at full power/2700RPM/mixture rich, airspeed between 120-140mph IAS, cowl flaps full open, CHT's were above 450 but below redline according to the gauge.

-After leveling off, WOT/2500RPM/mixture rich, 3500'MSL and 4500'MSL, cowl flaps open or closed, CHT's 390-400.

Is this abnormal?

[Bob_Belville]

4 minutes ago, par said:

I went for a quick flight today and paid close attention to my CHT's this time after M20F mentioned it. While I don't trust the gauge completely, here is what I saw today.

-CHT's were close to redline while IDLING to warm up the engine @ 1000RPM, even after I opened the cowl flaps. OAT was mid 40's.

-On climb out at full power/2700RPM/mixture rich, airspeed between 120-140mph IAS, cowl flaps full open, CHT's were above 450 but below redline according to the gauge.

-After leveling off, WOT/2500RPM/mixture rich, 3500'MSL and 4500'MSL, cowl flaps open or closed, CHT's 390-400.

Is this abnormal?

Sure would be for me. There's a lot potential factors. 

[par]

Couple other questions then. First, the plane just had an annual and the engine is in good health. Next, the gauge indicates the green arc STARTING around 400 degrees and doesn't redline until almost 500 degrees. Is this a design flaw? Finally, is it possible that someone installed the incorrect temperature probe? When I bought the plane, it came with a bad probe and no associated CHT's but that was fixed with a replacement. That mechanic did not exactly do the best quality work.

[N201MKTurbo]

You can buy a test pressure gauge for $10 

https://www.directmaterial.com/1-1-2-liquid-filled-pressure-gauges-1-8-npt-center-back-mount.html?gdftrk=gdfV26558_a_7c120_a_7c3251_a_7cPB158B_d_100&gclid=COiy2rje5MoCFUiFfgodZH4Gow

You can screw it in place of one of the front oil passage plugs.

If your gauge is accurate, then readjust your pressure regulator so your pressure is at the bottom of the green when the oil is hot.

[Shadrach]

15 minutes ago, Bob_Belville said:

Sure would be for me. There's a lot potential factors. 

You cannot really compare your injected angle valve to a carbed parallel valve. From what I am reading here, the O engine in the Cs and Gs runs 50-100df hotter than the IO Es and Fs all other things being equal.

[Bob_Belville]

1 hour ago, Shadrach said:

You cannot really compare your injected angle valve to a carbed parallel valve. From what I am reading here, the O engine in the Cs and Gs runs 50-100df hotter than the IO Es and Fs all other things being equal.

I think the M20C model has a CHT red line of 500 vs. 480(?) for the M20E.

[Guest]

8 hours ago, Shadrach said:

You cannot really compare your injected angle valve to a carbed parallel valve. From what I am reading here, the O engine in the Cs and Gs runs 50-100df hotter than the IO Es and Fs all other things being equal.

If the CHT's are that hot would it not suggest the carburetor main jet is too small?

Clarence

[par]

Any thoughts from the pros on why the stock CHT gauge has a green arc between 400-500 degrees? Was this done incorrectly back in the day?

[Shadrach]

10 hours ago, Bob_Belville said:

I think the M20C model has a CHT red line of 500 vs. 480(?) for the M20E.

I made that very suggestion in a different thread. It seemed that many of the C models on this board could use more fuel at WOT. I think one poster even called Marvel Schebler because his WOT FF around sea level was in the high 16gph range (IIRC). They told him that it was "just about right" (seemed low to me). Anyway, I think most folks are chalking it up to design deferences (piston oilers, less cooling fin area). I would be really troubled if I was seeing 400 in climb, much less cruise. I've never understood why a lower compression engine making less power should run so much hotter with the same cowl design.

The stock E and F models are absolute sweethearts when it comes to engine temps. On a standard day, I could climb  from SL to 10'000 at Vy and keep all CHTs well under 400.

Edited February 7, 2016 by Shadrach

[bonal]

On February 2, 2016 at 6:17 AM, M20F said:

I would second this, also may want to check out why your CHT's are so high.

I was thinking the same thing

[DonMuncy]

3 hours ago, par said:

Any thoughts from the pros on why the stock CHT gauge has a green arc between 400-500 degrees? Was this done incorrectly back in the day?

The thinking has changed. Perhaps the engine manufacturers didn't worry about long engine life as most people do now. Or perhaps the metallurgy has changed. But the modern thinking is that CHTs should be kept below 400df.

[carusoam]

Dp

[DXB]

15 minutes ago, DonMuncy said:

The thinking has changed. Perhaps the engine manufacturers didn't worry about long engine life as most people do now. Or perhaps the metallurgy has changed. But the modern thinking is that CHTs should be kept below 400df.

Yeah I get the feeling there is no clear consensus on what's ok for an O-360 in a C model.  When I got my plane, my CHTs on climb looked like those of the poster here - I'd have to hustle to keep in the 430s, and it could hit 450 if I insisted on climbing at Vy the whole way.  Cruise was no issue unless leaning aggressively.  The advice seemed to range from "Meh... these old C models run hot" (a well known MSC owner) to "OMG Do something NOW!" (Mike Busch).   Now after some work on the baffle, the hottest cyl gets to 400 but not much hotter, even if I climb steep, and I can lean much more. My main worry is that the plane was in Texas and Florida before I bought it, where it had 600hrs put on new Millennium cylinders.  I suspect they were treated pretty badly in terms of temps in that environment along with crappy baffling, and there was no engine monitor until recently. It will be a dilemma whether to replace or overhaul them when its time to overhaul the engine.  

BTW my oil pressure often runs in the top yellow arc at full power, but I haven't paid much attention- my bandwidth is still too preoccupied with the temps. 

[carusoam]

Two or three parts to this cooling challenge...

1) Lack of instrumentation:

  - The singe CHT and EGT sensors.

  - the small analog gauge on the far side of the panel.  Hard to read with any accuracy. 

  - EGT gauge has minimal information beyond where peak is and how many degrees ROP for one cylinder.

  - No FF instrument on most Cs, until recently.  Hard to tell if the second carb jet is on or not. Even the fuel level is hard to use to determine fuel used during the climb.

  -  Oil Cooling: oil is used for cooling.  The same instrument challenges apply here. Small and analog.  How well the oil radiator is working and its effect on CHTs can be a little unknown.

2) Air cooling: Dog house design and condition. Air doesn't like to flow smoothly in square channels and boxes.  It has a tendency to escape out of flowing through the areas that you want it to flow through.

3) Fuel cooling: Full throttle FF is near 2X cruise FF for most NA Mooneys.  

  - For My IO550  30+gph and 15gph roughly speaking.

  - For my O360 10-12 gph in cruise sort of.  I don't remember getting an accurate measurement of FT FF.

 

If I ever go back to an M20C...

1) JPI or equivalent.  4X EGTs and CHTs.  Imagine knowing your GAMI spread for a single carburetor?  How loose or tight is it?

2) FF and Carb temp on the JPI as well.  Digital fuel level sensors just because...

3) Updated Dog House/cowl closure design with good Maintenance.  Update M20C cowling design is 'In progress...'

4) Just add fuel injection....and war power intake mist water cooling 

I would think keeping cylinders cool would greatly minimize the carbon build up that can lock exhaust valves in place.  

Having this much data would give some insight to seasonal differences that you may want to be aware of.

Ross, how does this sound?...Does anyone use the blue box method of mixture control for a carbed engine climbing at FT.  Blue box EGT range is 2-300°F ROP?  Do the O360 EGTs go that low?

Just my thoughts of a PP, not a mechanic.

Best regards,

-a-

[Shadrach]

1 hour ago, carusoam said:

Ross, how does this sound?...Does anyone use the blue box method of mixture control for a carbed engine climbing at FT.  Blue box EGT range is 2-300°F ROP?  Do the O360 EGTs go that low?

Just my thoughts of a PP, not a mechanic.

Best regards,

-a-

If I had a C model, I'd do my best to be sure that I could get to 200ROP or richer on every cylinder. 250-300 would be better. But what do I know...There are many credentialed experts that say they just run hotter.  I start to get uncomfortable when CHTs get above 380.  I've only had to deal with anything close to that on rare occasions when I'm heavy and it's hot.