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Oil Temp

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Posted (edited)

Hello all,

I'm looking for any advice/operating temperatures for a ea-81 engine with a gear drive signal carburetor. My water temp is consistently running from 190F to 200F but the issue I'm having is the oil temp will reach the 250 mark in a short amount of time so i put a oil cooler on it inside the cowling in front of the engine with a shroud to catch the air coming in allowing it to of though the cooler and I replaced the probe and oil temp gauge. The engine is still reaching the 250 mark and I'm sure it would get hotter if I didn't land and turn it off.  i just got this plane and have no info on what the exceptionable ranges should be and I'm not finding a lot out their.  Any help would be greatly appreciated.    

 

 

Edited by David

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Posted

There are Subie experts here who can speak to the engine, but I would say it depends on the oil. 

When running a full synthetic, Mobil 1 for example, the oil can tolerate temperatures easily to 350 F or more before it begins to break down.  Weather the engine will melt at what temp I will let others comment on. 

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Posted

This evening I attached  a 5" fan to the oil cooler just to see if the little air produced by the fan would make a difference on the ground when taxiing. The water temp came up to temp quite rapid ( 4 minutes to get to 190F) and the oil temp slowly came up much slower then the other day.   After 15 minutes on the ground the oil temp reach 240.  My thought is if I were to put a hole in the cowling and have direct air flow to the cooler it should work fine.  Any thoughts? 

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Posted

What reduction unit do you have? If it is gear drive does it share oil with the engine? If it does you may need to run a motorcycle type oil similar to what I'm doing in my 912. With a belt reduction you should not be getting any excess oil heat. The EA 81 has a large oil pan, hold 5 quarts, exposed to air flow for cooling. Maybe a tight bearing in your re drive(if it's geared) causing the heat.

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Posted

What type of indicator/sensor setup do you have? Personally I'd question whether it's really getting that hot to start with. As a mechanic I don't want to ever see over 240 degrees on the oil. Most oils will start breaking down at or around 250. Also, once oil has broken down it will always get hot quicker. How is your oil pressure? Do you see it coming down quite a bit when the temps get hot? That's a very quick indicator something isn't quite right. If the pressure stays fairly stable (assuming you have a gauge), then I'd suspect the oil temp gauge/sender again.

If I were you, I'd do something to test the oil temp sender, such as pull it and put it in boiling water, that way you'll know what the temp is. Also be sure to changer your oil if you think it has gotten that hot. 

Of course the oil change is the quickest and easiest thing to do. Have you changed it since you purchased it? 

Just a couple thoughts. 

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Posted

I do have A gear drive that has the oil running from the engine,  and the oil presser does drop in the 25 range and less at idle when hot compared to 75 when cold.  I did put a new oil gauge and prob it and have had the same results of it reading the high temp.  Tonight I was able to cut an hole in the cowling and make shift a tube that allowed the air from the prop to go directly though the cooler.   After on the ground 15 minutes or more taxiing the temp reached 210 and seemed to hang their. is this still to hot? I'm thinking in the air it should do even better? Also is there a good way to check the bearing in the gear box aside from breaking it down?  

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Posted

Without details on the gearbox it's pretty tough. If it has tapered roller bearings and the preload is to high it will create lots of heat. The usual method is torq-o-meter to measure rolling resistance on the bearings to get preload. A little loose is one thing. To tight and it could seize up. Is this a manufactured unit? There should be set up specs from the manufacturer. The gear stuff is all about shear degradation of the oil. Apparently motorcycle oils have additives to combat this. Also, new style oils don't have the zddp(zinc) additives like they used to. EA 81's are old school engine. No roller lifters on the cam. I don't think that is you problem but it matters for longevity. I'm thinking tight bearing preload in the redrive. Water temp at 4000 rpm cruise with 5 pounds vacuum would be 185 degrees. 45 pounds oil pressure. 

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Posted (edited)

David,

Info from Chilton car manual 1970 - 1984 models:

These engines had an oil cooler when installed in a car.  Is your engine a turbo?  Oil pressure for most models is 36 to 57 psi - Some models just give 57 psi.  If you have the Serial Number, or know what year and trans it was for, I can look in my book to see which model you have and what the recommended oil is for it.  Depending on ambient temperature, some engines use 10W and others use 20W.  What oil are you using?  My book doesn't give an oil temperature range.  Possibly, you can get the oil temperature limits from the manufacturer of the oil.  I believe I have read that SOME motorcycle oils contain lots of zinc, which your engine probably needs to keep the cam/lifters lubed.

EDMO

Edited by EDMO

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Posted

210 isn't too bad if that's what you're getting on the ground and in the air. I agree that the redrive sounds like it could be culprit. Also what grade of oil are you running? If you're in a warmer climate you might consider going up a grade and use a tad bit heavier oil....don't go too crazy though. 

Test it out with the new oil and see what it does in flight. 

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Posted (edited)

210 isn't too bad if that's what you're getting on the ground and in the air. I agree that the redrive sounds like it could be culprit. Also what grade of oil are you running? If you're in a warmer climate you might consider going up a grade and use a tad bit heavier oil....don't go too crazy though. 

Test it out with the new oil and see what it does in flight. 

I would like to know how you hook up an oil cooler to this engine so that you have oil circulation thru it, or is the cooler just connected to the oil pan?   Any photos or diagrams?  EDMO

Edited by EDMO

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Posted

Ed. Honestly I have no idea about connecting an oil cooler to one. I haven't ever seen one on a Soob that I can remember. I can reach out to my brother. He's owned at least half a dozen of them through the years. If any of his have had them he'd know. 

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Posted (edited)

Ed. Honestly I have no idea about connecting an oil cooler to one. I haven't ever seen one on a Soob that I can remember. I can reach out to my brother. He's owned at least half a dozen of them through the years. If any of his have had them he'd know. 

Mine doesn't have an oil cooler, and I didn't see one on the Stratus either - I now wonder if the cooler on the cars was for the auto tranny, or the engine with a turbo?    Got to check my manuals on that one.   EDMO

Edited by EDMO

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Posted

I have been thinking, what if you were to make a duct that blew onto the oil pan instead of an oil cooler would it do the same thing as an oil cooler, or would it not be nearly as effective  as an oil cooler.  just a thought, it would be a lot less to go wrong. No oil lines to blow off? My thinking is for my Jabiru here, I have not heard real good things about the Jabiru Oil coolers.

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Posted

Here are some adapters that go under the oil filter so you can run an oil cooler.  Jabiru uses something very similar, although it doesn't have a built in thermostat.  The original Jabiru oil coolers can develop leaks over time.  Plenty of good coolers available for not a lot of money.  Jim Chuk

http://www.jegs.com/p/Earls/Earls-Temp-A-Cure-Oil-Thermostats/2872463/10002/-1

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Posted

I thought I was going to have my heating issued resolved after my last ground test, however the flight test was not good.   The temp in the air quickly jumped up to 250 and climbing.  Its as though the air is not leaving the cowling even with it being forced in.  Today I took the cowling off and ran the engine at 3000 RPM to see what it would do and the oil temp stayed at 180 in a 20 minute run.  I did notice that the gear drive seems to generate a lot of heat I don't know if this is normal but I could feel heat distributed to the base of the prop plate and it was quite warm.  My gear drive says ROSS AERO   AZ.U.S.A.  

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Posted

Can you upload pictures of your cowling? Specifically the bottom where the air should exit as well. If it doesn't have a lip, you might be right about the air not exiting. With the Cessna Ag wagon if it didn't have it the engine would get hot really fast. It is literally about a two inch lip that sticks almost straight down creating more of a low pressure area so the air is drawn through the engine cowling. 

Something to think about. 

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Posted

Is your rad inside the cowling? Cheek rads? I'm still suspicious of the reduction drive. Hopefully they're still in business. Not directly related but thinking of heavy trucks I own I generally see water and oil temps pretty similar. In your case:250 oil and 190-200 water is telling you something is tight. EA81 on it's own has no reason to create that much oil temp.

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