What is this cheesy material in my oil cooler?

CharlieTango

CharlieTango

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CharlieTango
We are doing a hot flush on my oil cooler. My Rotax 912 ULS now gets hot oil temps when climbing.

This yellow material is a mystery, does anyone know what it is?
 

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CharlieTango said:
We are doing a hot flush on my oil cooler. My Rotax 912 ULS now gets hot oil temps when climbing.

This yellow material is a mystery, does anyone know what it is?
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Oil Additives and detergents, crystallized and burnt.
 
I'd probably send it to Rotax and ask them, but I'm paranoid that way.

Is it "hard" or "plyable"? What does it feel like?
 
CharlieTango said:
Nick,

Can you tell me more? Is that a guess or do you know?
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If it were that I would expect it to be hard. Not cheese like.

I'd just be guessing at this point. Someone on here will know way more then I do. Might be worth asking Rotax.
 
CharlieTango said:
Nick,

Can you tell me more? Is that a guess or do you know?
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Without holding it in my hand, its a guess, but I will say that I had something similar on a VORTEC engine a while ago, and that was what it turned out to be.
 
Condensation,mixing with the oil after shut down.
 
I've never seen anything like that in the oil of a Rotax (or any other engine, for that matter). I do hope you plan to do an oil analysis.

I've uploaded a copy of Rotax's oil recommendations for the 912 series, in case you don't already have one. Nothing in there about yellow deposits, though.

How's the coolant look?

-Rich
 

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frfly172 said:
Condensation,mixing with the oil after shut down.
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That was my guess since the engine is air cooled.
Or perhaps someone left the dip stick out during a wash job or rain storm.
 
RJM62 said:
I've never seen anything like that in the oil of a Rotax (or any other engine, for that matter). I do hope you plan to do an oil analysis.

I've uploaded a copy of Rotax's oil recommendations for the 912 series, in case you don't already have one. Nothing in there about yellow deposits, though.

How's the coolant look?

-Rich
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Coolant looks fresh and coolant temps run 40 degrees lower than my oil.

The hot flush people don't know what it is so I plan on sending in the oil filter as well as a sample of the mystery contaminant.
 
JOhnH said:
That was my guess since the engine is air cooled.
Or perhaps someone left the dip stick out during a wash job or rain storm.
Click to expand...

That's what I would suspect except for the brightness of the yellow. Also, in my experience, water usually causes deposits that have a more fluid consistency, like mayonnaise or hand cream. The deposits in the picture look sort of crumbly to me.

-Rich
 
JOhnH said:
That was my guess since the engine is air cooled.
Or perhaps someone left the dip stick out during a wash job or rain storm.
Click to expand...

The 912s are liquid-cooled, by the way.

-Rich
 
RJM62 said:
The 912s are liquid-cooled, by the way.

-Rich
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I figured that out shortly after I posted. :redface:
So perhaps it could be coolant leaking into the case. That could help explain the overheating.
 
From the looks of it, something has bought the farm. Keep us posted as to what you find. But I think something has gone bad and these are pieces of that part. It could be an oil pressure relief valve of some sort. With it being a 912 it could be any number of things.
Water in the oil it is not. Antifreeze in the oil it is not. Antifreeze in your oil will make the oil look like milk from the water. Water in fuel will not cause this either.
Your engine ate itself somewhere. I would lay 5 bucks on it.

Tony
 
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I would also say these parts went through the oil system and ended up here before entering the filter. Your seeing a rise in oil temps because something is plugged and this part is running hot. It will not show up in water temp but will show up in oil temp. It could be a plugged passage in the crank and a main bearing is running hot or something like this.
Until you find out what this is, if it was mine, I would ground this airplane.

My 2 cents.

Tony
 
1600vw said:
I would also say these parts went through the oil system and ended up here before entering the filter. Your seeing a rise in oil temps because something is plugged and this part is running hot. It will not show up in water temp but will show up in oil temp. It could be a plugged passage in the crank and a main bearing is running hot or something like this.
Until you find out what this is, if it was mine, I would ground this airplane.

My 2 cents.

Tony
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That sounds better than my answer.
Follow that advice.
 
RJM62 said:
That's what I would suspect except for the brightness of the yellow. Also, in my experience, water usually causes deposits that have a more fluid consistency, like mayonnaise or hand cream. The deposits in the picture look sort of crumbly to me.

-Rich
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Yup. Water and oil make a chocolate-milk sort of gunk, sometimes more gray than brown. Never seen yellow like that. Would it be dye from glycol coolant?

Dan
 
Dan Thomas said:
Yup. Water and oil make a chocolate-milk sort of gunk, sometimes more gray than brown. Never seen yellow like that. Would it be dye from glycol coolant?

Dan
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50/50 Dexcool since she was new.

She ran cool for the 1st 2 years and then for the next 6 years got incrementally hotter and hotter. Other CTs of my vintage have similar oil overheating issues. The problem has been illusive and I'm the 1st to hot-flush the oil cooler.
 
Did you buy the airplane new? Is it possible somebody tried to repair a leaking cooler with some kind of sealant goop at some point?

Are you using Aeroshell Sport +4 or something else for oil?
 
Capt.Crash'n'Burn said:
Then paraffin wax build-up is a possibility. It would match the other symptom, the engine running progressively hotter over time.
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Paraffin wax build-up seems the mostly likely answer so far.

I wonder if it is limited to my oil-cooler which is a 28micron filter and my oil filter or is it an issue internally too? If it returns to running cool I would guess it was limited to cooler or cooler and filter.
 
Sometimes strange gunk occurs when you have a blown head gasket. Pressure pushes coolant into the crankcase. Coolant mixed with the Mobil 1 might become yellow instead of the milky white that is common to this type of problem.
Also might check for intake leaks.
 
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