Continental 0-200A Newly Overhauled Oil Temp

Mooney Fan

Mooney Fan

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Mooney Fan
Brought home a 75' 150M the other day. 13.5 SMOH with new Superior Cylinders. Checked filter at 10 hours with no metal noted. Good compressions. Still working mineral oil and waiting for oil burn to stabilize. Right now its blowing anything over 4qts on the belly.

Oil pressure is OK but that oil temp reading at 55F degrees, 2500 rpm seems high. But then again, I've never broke in a fresh engine and cylinders. The engine has new Airform baffles. Looking into the cowl air inlets the baffle blocks an awful lot of those cylinders up front. Plus, someone siliconed the back of the baffle to the cylinder base. Typical? I can't find any detailed guidance on that.

Looks like I'm running at 210 degrees? We plan to check he gauge first if things don't cool down

Thanks

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What's the book value require? 210F isn't too hot.
 
It's in the green ... what problem are you trying to fix?

It may come down a bit more with more time on the engine.
 
Using silicone on baffles, carelessly, can get silicone into the fins and block airflow.

You didn't have this airplane with the old engine and old oil temp reading, so you have no idea if that gauge is trustworthy. That model might or might not have an electric oil temp, and poor engine grounding can cause high temperature readings. The alternator's charge current does it, trying to reach the airframe through dirty/loose grounds, even paint on that overhauled engine, and if it encounters resistance it will run some current though control cables, and though pressure and temperature gauge sensors, spiking their readings.

I used to check gauges by taking the sensor out and immersing it in a can of hot water with a candy thermometer in it, and then warm the can further with a propane torch (carefully, away from the airplane and engine using jumper leads) and see what the airplane's gauge said when the water started boiling.

As far as the new baffles blocking the cylinders, I doubt it. This stuff is sometimes not intuitive. The baffles are designed to force the air to follow as much cylinder and head finning as possible, from directly above.

This is the baffling for your '75 model. Make sure numbers 33 and 52 are in place, between the cylinders and heads, on both sides of the engine. These often get left off, and air escapes without cooling anything. It hampers ALL the cooling by allowing the pressure differential to decrease. Earlier 150s didn't have them.

Look in the front with a flashlight and make sure the baffle seals are contacting the cowling properly. Air escaping there does no cooling, either.

Baffles 27, 28, 31 and 32 had better be there. They direct air along the bottom of the crankcase and at the oil tank, which is normally the only oil cooler an O-200 has.


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Dan Thomas said:
Using silicone on baffles, carelessly, can get silicone into the fins and block airflow.

You didn't have this airplane with the old engine and old oil temp reading, so you have no idea if that gauge is trustworthy. That model might or might not have an electric oil temp, and poor engine grounding can cause high temperature readings. The alternator's charge current does it, trying to reach the airframe through dirty/loose grounds, even paint on that overhauled engine, and if it encounters resistance it will run some current though control cables, and though pressure and temperature gauge sensors, spiking their readings.

I used to check gauges by taking the sensor out and immersing it in a can of hot water with a candy thermometer in it, and then warm the can further with a propane torch (carefully, away from the airplane and engine using jumper leads) and see what the airplane's gauge said when the water started boiling.

As far as the new baffles blocking the cylinders, I doubt it. This stuff is sometimes not intuitive. The baffles are designed to force the air to follow as much cylinder and head finning as possible, from directly above.

This is the baffling for your '75 model. Make sure numbers 33 and 52 are in place, between the cylinders and heads, on both sides of the engine. These often get left off, and air escapes without cooling anything. It hampers ALL the cooling by allowing the pressure differential to decrease. Earlier 150s didn't have them.

Look in the front with a flashlight and make sure the baffle seals are contacting the cowling properly. Air escaping there does no cooling, either.

Baffles 27, 28, 31 and 32 had better be there. They direct air along the bottom of the crankcase and at the oil tank, which is normally the only oil cooler an O-200 has.


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Thanks for the knowledge. I'll verify next time out.
 
Presence may not be enough.

Not #33 is asymmetrical with one leg longer.

Incorrect side to side positioning will not direct cooling air and also

other other cylinder will have the air exit restricted.

#51 should pull the baffle tight so air cannot bypass the fins.
 
So today I changed the oil in the 0-200A. Done with the mineral oil (19 SMOH) and put in Phillips XC-20W-50. I noticed my oil temps subsided some but my oil pressure has dropped. The pic in the opening post shows my pressure and temp using Mineral Oil. And here is todays flight. Looks to me like a 10-15 psi drop after todays change. At idle is just above the red on the low side.

My last 2 planes had solid mid-time engines with no issues. Seems like this one is trying to tell me something or am I over analyzing things?

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The pressure relief valve might need shimming or adjusting. Were you using a straight-weight before, like 80 or 100?
 
FWIW, my C150m oil temp always settles on the "T" of temp, both before and after major overhaul.

Lots of factors at play here, including a 50 year old gauge and sender. Probably best to ask an A&P. One simple thing they can check is to make sure the oil screen was removed when the oil filter was added on. Sometimes this step is skipped. The oil temp probe goes into the back of the screen.
 
samiamPA said:
FWIW, my C150m oil temp always settles on the "T" of temp, both before and after major overhaul.

Lots of factors at play here, including a 50 year old gauge and sender. Probably best to ask an A&P. One simple thing they can check is to make sure the oil screen was removed when the oil filter was added on. Sometimes this step is skipped. The oil temp probe goes into the back of the screen.
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Thanks all. I have spoke with George Coy who did the overhaul. He suggested I switch to W100. Wanted me to check for metal in the Oil filter and I found none. And the screen has been removed. Plan to dump the XC and put in W100.
 
samiamPA said:
One simple thing they can check is to make sure the oil screen was removed when the oil filter was added on. Sometimes this step is skipped. The oil temp probe goes into the back of the screen.
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The spin-on filter adapter has a port for the oil temp probe. When the screen is removed, so is the whole screen housing.

Unless, of course, they used the adapter that bolts onto the oil port on the left aft side of the engine. Don't see many of those at all. I don't like them; that filter is a long way off the case and it's heavy and the adapter base is small, so it is subject to cracking and breaking with all the vibration.
 
Since the O-200 does not have an accessible suction screen I like to suggest drawing oil through a paint strainer.

Since anything to the filter/ pressure screen must first travel that route will aid in diagnosis.
 
During the oil change is an ideal time to INSPECT the baffles and seals per #4 .

You are trying to make hot air move downhill via differential pressure .

ANY unsealed gaps will reduce the delta.

Loose inter cylinder baffles will reduce cooling also.
 
I’ve come to find what looks like the inner cylinder baffle is 180 out. By looks of the drawing the longer flange should face aft. Mine are fwd. I’ve attached a pic

How do I rotate the baffle? It’s riveted to the T mount . And does the baffle come out the bottom?

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Likely swapping sides will correct.

It will come out the bottom by squeezing with finesse and special words.

Intake Pipes make the task more challenging.
 
Magman said:
Likely swapping sides will correct.

It will come out the bottom by squeezing with finesse and special words.

Intake Pipes make the task more challenging.
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I noticed the push rod tubes make it problematic as well underneath. Now I see why maybe they are left out on purpose lol...
 
Update- A couple of cuts and words I don't often use I was able to remove the inboard inter-cylinder baffle on both sides and swap them side to side. They were indeed installed 180 out.

Look fwd to next flight to see what impacts it has if any on oil temps.
 
GeorgeC said:
It'll change to being too cold, like mine :rolleyes:
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Well, wish I could say some of the same but no joy. Temps near top of the green band.

80 degrees at 1500', 2450 RPM, turns in the same temp results as my opening post pic at 55 degrees 2500 RPM.

Next up- Testing the Rochester Oil Temp probe for accuracy.

Its still green though (sigh)..
 
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So the baffles on the engine are correct and force air between the fins and the Soft Seals allow no gaps to prevent pressure build up above the engine?

Ignition Timing can cause heat issues. Check via Timing Light even if mag drop is good.

Leaning the mixture should result is about a 20 rpm increase at all power settings. If no increase you are running LEAN.
 
Did anyone check the diagram I posted in post #4? There are baffle sections that run along the bottom of the crankcase to cool it and to dump the air over the oil tank, cooling it further. The air comes through the two small holes in the nosebowl under the prop. If those baffle pieces are missing, or if their seals are shot, not only is the air not getting at the case and tank, but the air coming through those holes raises the pressure under the engine, slowing the cooling flow from above.
 
I’m thinking whoever put #33 in reversed is likely clueless about baffles and
PROPER installation.

I do sort of put myself in that category at times. There are several aircraft types that the baffles are “ baffling “ to me. The Parts and Service Manuals
become my friend at that time. The Piper Colt system is sort of unusual.
Modifications to make things “ better “ is not in the cards.
 
Magman said:
So the baffles on the engine are correct and force air between the fins and the Soft Seals allow no gaps to prevent pressure build up above the engine?

Ignition Timing can cause heat issues. Check via Timing Light even if mag drop is good.

Leaning the mixture should result is about a 20 rpm increase at all power settings. If no increase you are running LEAN.
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I’ve been thinking about the timing. It is set to 28° vice 24° as per Superior Service letter. Have read in one case where dropping it back down to 24° resulted in noticeable drop in oil temps with no noted decrease in performance
 
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Dan Thomas said:
Did anyone check the diagram I posted in post #4? There are baffle sections that run along the bottom of the crankcase to cool it and to dump the air over the oil tank, cooling it further. The air comes through the two small holes in the nosebowl under the prop. If those baffle pieces are missing, or if their seals are shot, not only is the air not getting at the case and tank, but the air coming through those holes raises the pressure under the engine, slowing the cooling flow from above.
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Yes. The lowers are there. While my 140 had the small holes under spinner this 150 cowl only has the ovals.
 
I had a long term perplexing problem with over heating with an O200 in a ‘67 150F.
Turned out that it was the fuel nozzle in the carburetor. Many of the fuel nozzles on recent o/h kits are marginally undersized. It took several years to convince my mechanic. We ordered an oversized nozzle from Kelley Aerospace, and voila! Fuel burns and oil temperatures became Normal!
 
Dan Thomas said:
The pressure relief valve might need shimming or adjusting. Were you using a straight-weight before, like 80 or 100?
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The O-200 does not have an adjustable oil pressure relief valve. It has a spring loaded plunger and seat in the accessory case. Adding washers and so forth can only affect the pressure at which it pops-off, not the running pressure. Once the oil is hot, the pressure is that which provided by the pump forcing the oil through the various galleys and passages as the plunger is closed on its seat.

However, if the seat is not conforming well with the plunger nose there may be a perpetual leak around the plunger which can lower oil pressure. Lapping the two parts may help, there are internet discussions on same. Normally an overhauled accessory case will have the seat recut (see the 8130 form for example), but it's not married to the new plunger per se.

205 to 210 seems ok until the rings are properly seated. In principle they should be seated by now if the engine was run hard to break it in - that's important.
 
Steamflyer said:
The O-200 does not have an adjustable oil pressure relief valve. It has a spring loaded plunger and seat in the accessory case. Adding washers and so forth can only affect the pressure at which it pops-off, not the running pressure. Once the oil is hot, the pressure is that which provided by the pump forcing the oil through the various galleys and passages as the plunger is closed on its seat.
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That is called a relief valve, and it is used to control the pressure. The manufacturers even sometimes call it a regulator. It is adjusted by shimming, as I said, and if all the bearing clearances are where they should be, and the pump is not scored and worn, that valve will constantly be bleeding off some oil to keep the pressure within limits, except at low RPM or at idle with hot oil. It doesn't just "pop off" to relieve excess pressure when the oil is cold.

From the O-200 overhaul manual:

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Dan Thomas said:
That is called a relief valve, and it is used to control the pressure. The manufacturers even sometimes call it a regulator. It is adjusted by shimming, as I said, and if all the bearing clearances are where they should be, and the pump is not scored and worn, that valve will constantly be bleeding off some oil to keep the pressure within limits, except at low RPM or at idle with hot oil. It doesn't just "pop off" to relieve excess pressure when the oil is cold.

From the O-200 overhaul manual:

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This is all true, but don't think it's setting the oil pressure by "chattering" open and closed in my experience. At start up it's open typically and then closes when hot running, and the engine establishes it's predetermined pressure.

The alternative interpretation is that the running pressure is set by a small, continuous, but finite leak at the plunger. In this case shimming or a bigger spring would in fact bring pressure up. Then at idle the plunger closes and the pressure drops. Never was quite sure which it was.
 
Get you a good infrared temp gun. Go flying, when you get back you can open the oil door and shoot the back of the oil sump and see what it says. Or pull the dipstick out and shoot down the filler neck.

I think there about $29 on Amazon.
 
Steamflyer said:
This is all true, but don't think it's setting the oil pressure by "chattering" open and closed in my experience. At start up it's open typically and then closes when hot running, and the engine establishes it's predetermined pressure.

The alternative interpretation is that the running pressure is set by a small, continuous, but finite leak at the plunger. In this case shimming or a bigger spring would in fact bring pressure up. Then at idle the plunger closes and the pressure drops. Never was quite sure which it was.
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It doesn't chatter. It can't. The hollow nut acts as a cylinder for the piston, and it fills with oil, damping the piston's movement. It floats off the seat just as far as necessary to balance oil pressure against spring pressure.

The bearing clearances don't change much with temperature. But the oil viscosity does, and its velocity changes with pump RPM, so hot oil at low RPM won't hold that plunger off its seat and the valve closes. If the setpoint is 35 psi but the pressure in cruise is 30, the valve is closed. Likely pump bore scoring, or excessive clearances are present.
 
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Mikey52 said:
Get you a good infrared temp gun. Go flying, when you get back you can open the oil door and shoot the back of the oil sump and see what it says. Or pull the dipstick out and shoot down the filler neck.

I think there about $29 on Amazon.
Click to expand...

That’s what my mechanics did. However it only affirmed what the a/c mechanical engine gauge was indicating. In my instance, oil pressure wasn’t an issue. It held 50psi cold and 35-40 hot, and 10 hot at idle. Switching oil didn’t help. Lowering magneto timing and running full rich didn’t.
Taking off from 700’ msl, a climb to pattern altitude had oil temperature at redline. To climb out required intermediate leveling off for 3-5minutes at reduced power to allow oil to cool enough to continue.
After replacing the fuel nozzle, it was essentially impossible to get temperatures above 180-190deg. Mag timing was returned to original specs. The nozzles aren’t that expensive. ~$135 circa 2016-‘17.
Peace of mind was priceless!

Added: originally, engine shut down by leaning would give a rise of about 20rpm. After replacing defective fuel nozzle, rise was closer to 50rpm… definitely more noticeable.
 
AeroLudite said:
Added: originally, engine shut down by leaning would give a rise of about 20rpm. After replacing defective fuel nozzle, rise was closer to 50rpm… definitely more noticeable.
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That RPM rise on ICO is controlled by the idle mixture adjustment and has nothing to do with the main fuel nozzle. The airplane's service manual tells mechanics how to adjust it to a specified RPM rise, if the mechanic ever reads the manuals. Many don't.

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Edit: I decided I'd better look up the C150 (O-200) mix adjustment. It's done at 1000 RPM:

1690476208452.png


The wrong idle RPM can affect the ICO rise. It must be set first. Then the idle mixture is set.
 

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Mikey52 said:
Get you a good infrared temp gun. Go flying, when you get back you can open the oil door and shoot the back of the oil sump and see what it says. Or pull the dipstick out and shoot down the filler neck.

I think there about $29 on Amazon.
Click to expand...
The oil sump will easily read hotter than the gauge if there's an oil cooler in the system. The gauge takes its reading from the oil inlet to the engine, usually between the pump and all the working bits. Aim the gun at temp sensor or the housing or case part it is in.
 
Not many c-150's have an oil cooler with the o200. It was an option though. And the oil flows from the sump to the pump to the screen(if installed)/temp bulb housing, then out to engine.

If his oiled temp reading is high, and the sump is cooler, I would suspect the bulb/gauge.

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Mikey52 said:
Get you a good infrared temp gun. Go flying, when you get back you can open the oil door and shoot the back of the oil sump and see what it says. Or pull the dipstick out and shoot down the filler neck.

I think there about $29 on Amazon.
Click to expand...

Thanks. I have one on the way. Today I took the one we use for medical which also has a setting for 'things' that reach up to its 215 degree limit.

After flying about 30 minutes the oil temp was up towards the end of the green band. Landed and once off the RWY I shut down (uncontrolled field no one around) and quickly shot the oil temp bulb and it was 178 degrees. Shot the temp down the oil dipstick tube and it was in the 170's as well. Oil sump same.

I finally got everything I need to test that Rochester oil temp probe and hope to get that done in the next week or so.
 
Argggg . Out here this morning to test oil probe I found they didn’t remove the screen after adding oil filter. I thought that was mandatory not optional.
 
Argggg . Out here this morning to test oil probe and look what I found. They didn’t remove the screen after adding oil filter. I thought that was mandatory not optional
 
Check the STC instructions for your plane, but i believe it should be removed. It is silver soldered or brazed to the plug. On mine, they didn't take the trouble to unsolder it, they just cut it flush. On first annual the IA threw it on the table, and said that's no good, while I was researching other needed parts. Quickly found a replacement screen on eBay and ordered it. The couple days it took to show up, I found Stc instructions. Does any one need a new old stock O200 oil screen. It just the screen not the plug screen combo.
 
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