TCM IO-240B low oil pressure

[akoch]

Hi guys,

found myself struggling with this one, and at this point a bit lost what to do next. The engine starts up with normal high-pressure oil indication, cold oil. After the run-up, once the oil temperature comes up closer to the green zone, or into the green zone, the oil pressure drops: still in mid or lower green at high rpm, and at or below the redline at idle.

What I've done so far:
- changed oil (for the heck of it, since wanted to check the filter)
- cut the filter, inspected - it is clean, no metal, but a few bits of carbon (which is normal?)
- suspected the oil pressure control valve - removed, cleaned and polished the valve seat; replaced the valve spring with a bran new one

And... no change, still at or below red line oil pressure once the engine warms up. Could you guys give any ideas/tips at what to try next? Vernotherm? Something else?

Thanks much!

[ahramin]

Tried calling TCM?

[Colonel Sanders]

Is oil temperature indication perfectly normal?

Did oil pressure indication suddenly change, or was this a gradual, smooth change?

Is oil pressure indicator mechanical or electrical w/remote sender?

What oil are you running?

[hangarline]

The oil pressure limits on this engine are 10 PSI at idle, which is really hard to judge on a guage that has few markings on it. Operating limits are 30-60 PSI, so if you are getting these numbers, you are probably OK, however you could hook up a good direct reading guage with calibrated indications to verify. If you are not already, I would try a straight weight W80 or W100 oil and see if this helps.

[akoch]

I switched from the Phillips oil to Aeroshell 15W50, about 70h ago. The issue with the oil pressure came up just recently.

The oil temperature indication while normal and still within the green operating temperatures, has actually changed along with the oil pressure issue. Before, the oil temp was always consistently low: never reached green during runup, would come up to lower green section during climb-out, and would be again just below the green during cruise. Now it firmly planted in the middle of the green for all modes, which is a certain change.

Did oil pressure indication suddenly change, or was this a gradual, smooth change? That I can't say (the plane was also flown by my wife and her instructor), but it suspect it was a fairly quick change.

The oil pressure indicator is electrical, with the oil pressure transducer sending the readings. I thought of the transducer going bad, but the suspicious oil temp change that co-insided indirectly tell me that it is something else.

[akoch]

The oil pressure limits on this engine are 10 PSI at idle, which is really hard to judge on a guage that has few markings on it. Operating limits are 30-60 PSI, so if you are getting these numbers, you are probably OK, however you could hook up a good direct reading guage with calibrated indications to verify. If you are not already, I would try a straight weight W80 or W100 oil and see if this helps.

This I have not done (my mechanic does not seem to have the direct reading gauge). This will tell exactly what is going on. But what bothers me is that it is a certain change from the oil temp/pressure before. So the reading is likely to confirm that the pressure is low, and then I have the same question, what to do about it?

Just a question - if I switch oil weight, and say it helps somewhat. Will the issue go away say partially, and this would be a step to troubleshoot this?

[akoch]

Update: called TCM and they suggested to leave it at that not seeing a problem.

The tech said something like "probably the engine at your 600h finally settled down".... The oil pressure in idle should be about 8-10PSI, his only concern was that in cruise it is at or above 30PSI which it is.

So I figure I'll just continue on flying. What alarmed me is the noticeable change in the temp and pressure reading values. So it is finally came to being "normal" now? Time will tell I guess.

[Colonel Sanders]

If the oil temp indication had not changed, my bet
would have been a connector on the oil pressure
sensor - a bad oil pressure reading, with the actual
engine oil pressure unchanged.

But the fact that your oil temp has increased
correlates with a real decrease in oil pressure.

I would want to know why. Is this common with
TCM IO-240 engines?! I have flown a TCM IO-360
engine for 42 years now, and it's oil pressure has
never, ever changed.

I know the viscosity of 15w50 and W100 straight
grade is supposed to be the same when hot, but
if it's not too cold, try running 100 at your next
oil change. You're on the left coast, correct?

[akoch]

Pacific coast, yes.

I'll try the W100 oil next time. It bothers me that the pressure changed. But the Continental says it is not a concern, and the engine is operating now more "as it should" with the higher oil temp and lower pressure in idle now than before. Go figure. I'll report back if something changes.

[Colonel Sanders]

I wonder if we are looking at this from the wrong direction.

Is it possible that something increased the oil temperature,
and in turn that dropped your oil pressure? What could
increase your oil temperature? Perhaps some baffling or
seal failed, so there is less air going through the oil cooler?
Is your oil cooler plugged up with bugs and crud?

Oil temp (and hence viscosity) is the same at startup - is
your cold oil pressure (for the first minute after start) low
or same as before?

This bugs me. Figure out what's going on. This is not
rocket science. Pull your cowls and look carefully at
your baffles and seals and oil cooler. Something might
be in poor condition there.

Vernatherm opening at correct temperature?

Dumb idea: I have no idea what the wx is on the left
coast. Are you guys having a heat wave? That by
itself could lead to higher oil temps (and lower oil
pressure) if for example up until this point you had a
cooler than normal spring and summer.

You don't have the winter kit still on, do you?

[Heliian]

Is there an oil cooler on the a/c? If there is, is the bypass valve functioning correctly?

[Spinner]

If this is a diamond aircraft I can add a few things.

Oil pressure gauges in the diamond are very inaccurate. Perhaps even if not a diamond check the calibration of your gauge. Diamond now sells them as a transducer/gauge kit which is supposed to be better . We usually tie the sender into a line with a calibrated gauge and check it. Common error seems to be 10-15 psi at lower red line (which is a lot).

Continental has brought out both a newish looking double spring for the regulator and also a single spring which seems to be a little better.

as said by the colonel oil temp seems to make quite a difference on these engines. We are happy on a summer day if the pressure is staying over thirty-five. We caution pilots to avoid long ground runs and steep climbs because once that oil temp starts upwards it is hard to stop on a diamond.

hope this helps.

[akoch]

Thank you Spinner!

Yes, this is the DA20-C1. Perhaps I'll order the transducer/gauge kit as you suggested. Otherwise everything else is checked out good, can't find any faults so far. As I mentioned, it the change in the readings that caught my attention. Perhaps the warmer weather/thinner oil combination made the difference enough for the gauges to start reading differently. Will monitor it.

[Colonel Sanders]

Warm wx makes a difference! I remember a few years back,
sitting and waiting to take off for an airshow in Central America,
idling in the hot summer heat.

We were delayed and delayed, and I think I saw 260F or 270F
on the oil temp before I shut it down. That was in an S-2C
(AEIO-540) running straight W100. In retrospect we should
have been using straight W120.

Free advice: after you cook the oil like that, as soon as possible
drain it and replace it. People here won't agree with me, but the
hotter you run your oil, the faster you use it up.

More free advice, worth what you paid me for it: if you're seeing
very high oil temps (eg summer jumper dumping) do NOT run
multigrade. The VI's will break down and you are left with the
base oil. For very high oil temps, run straight grade. At least
W100, perhaps W120. And change it every 10 hours.

I only run W120 in radial engines. I don't run that 25w60 junk.

Yes, you have to be careful about the cold starts with thick
straight grade, but if your oil temps are over redline it's probably
not below 0C in the morning. I hope.

[hangarline]

OK, so after reading your additional posts, it does appear that your problem is stemming from the increase in your oil temp which of course will lower your oil pressure. So like Colonel Sanders said, check for the reasons why your temperature went up. Obvious causes are, baffling, oil cooler restriction, oil level (I know this sounds simple, but it happens). Have you checked cylinder compression? A loss of compression past the rings can raise oil temp. And for sure get rid of the 15W50 oil. I know many here will disagree, but that oil does not belong in any engine. My advice, run W100 during the summer and go back to the Phillips 20W50 during the winter. It only took 70 hours after you started using the 15W50 to show a problem, but I would take a good guess that it caused a compression problem for you and this may be why your temp went up and subsequently pressure down. While I don't really like the answer that Continental gave you, reading between the lines, they are trying to tell you that if the temp and pressure are within the limits of the Type Certificate, then the engine is still serviceable. If you think the temp and pressure change happened in a short period of time, then you should investigate as to the reason(s).

[akoch]

Thank you guys. It makes sense what you're saying regarding the oil viscosity, baffling etc. I will re-check the baffling tomorrow, it is always possible it was re-assembled incorrectly and is affecting the temps during the warmer weather now. And I'll run the current oil a little bit (just changed it again), and then change to W100.

I'll also see if I can get a few bugs out of the oil cooler, there are certainly a good few sitting in there comfortably.

[Heliian]

Diamond service bulletin regarding oil temps.

[Colonel Sanders]

Thanks Helian!

Baffle seals - I knew it! Baffles and seals are incredibly
important, and receive very little attention.

[akoch]

I'll check the seals today and fly it a bit to see what happens. Thank you!

[Spinner]

We looked into getting the higher capacity oil cooler and found that there were none available and had not been for a while. (not to mention hellish price)

Changed an oil pressure gauge today that had a 20 psi error in it. My suggestion before you go and invest in a new oil pressure gauge is to have the old one checked with an external gauge or tie an external gauge in where the aircraft Hobbs meter sender mounts on the engine. This will tell you the real time engine oil pressure.
With the flight training going on we have a lot of students that do double starts (hit the start switch with engine already turning). This seems to do a great number on the starter gear and also the aft crankcase gear. This in turn allows metal to float around the engine and rather than get caught in the filter it winds up on the drain plug and also scarring the poppet valve for the oil pressure. If you find any metal on the drain plug when you change the oil you may want to look at the starter.

We have not tried the straight oils (yet) but it is a thought for these engines.

The oil pressure gauge/transducer combo is pn: 22-7930-10-00 (around 200-300 dollars)

good luck!

[akoch]

20 PSI error, wow!

I own this da20, so it is not really used for training. At least the thing with the starter grinding the gears is not happening.