Oil cooler thermostat sticking?

Jeanie

Jeanie

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Jeanie
Well, Sam is breaking in the engine on the decathlon that I am buying and the first flight it overheated to the point that the oil gauge pegged. However, the CHTs were fine. The next morning he flew the plane the oil was hotter than normal but didn't go over 240 and the ambient temp outside was cooler also. He's flying this plane in El Paso - HOT outside there.
He talked to someone about it - not too sure who - and they suggested that maybe a thermostate in the oil cooler is sticking.
Does that make sense? How do you unstick a thermostat?
 
It's either the vernatherm is not working properly or the oil cooler is clogged. If it's a fresh overhaul on the engine was the oil cooler overhauled as well?
 
Rotor&Wing said:
It's either the vernatherm is not working properly or the oil cooler is clogged. If it's a fresh overhaul on the engine was the oil cooler overhauled as well?
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~~~~ I don't know if it was or not. I'll ask. And it wasn't a complete overhaul, just rehoning of some cylinders, replacement of rings, replacement of the cranskshaft, mags and maybe a cylinder as well. I don't have all the information at hand.
 
Jeanie said:
~~~~ I don't know if it was or not. I'll ask. And it wasn't a complete overhaul, just rehoning of some cylinders, replacement of rings, replacement of the cranskshaft, mags and maybe a cylinder as well. I don't have all the information at hand.
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FYI In an engine breakin things will run a little hotter than normal.

After a top overhaul a couple of years ago I chased high oil temps down that just did not seem to go away. The oil lines were due to be replaced so that was the first step and it helped, a little. That kinda told me that the oil was not moving very well through the system and got me to thinking about the oil cooler. I asked the mechanic to look at it and he did the typical field service on the oil cooler. That is to say he flushed it several times and got some gunk out of it. But that did not solve the problem. I started to suspect the veritherm but in the end decided the cheaper and more likely issue was that the oil cooler was gunked up and field service really does not work.

I based that on what I read from these guys, http://www.oilcoolers.com/, and from what I had sussed from speaking to other owners. I then ordered a new oil cooler and the problem was solved.

I don't know if this is the issue you have been having, but if the oil cooler is older and was only flushed in the field it is something you may wish to factor into your troubleshooting.

Here are a couple links to my adventure with high oil temp

http://www.pilotsofamerica.com/forum/showthread.php?t=20506&
http://www.pilotsofamerica.com/forum/showthread.php?t=18942&
http://www.pilotsofamerica.com/forum/showthread.php?t=18052&
 
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Thanks, Scott, I just sent your post info to the guy breaking in the engine.
 
I once had a 172 with a new engine that wouldn't keep its oil temp below redline. Did a bunch of stuff that made little difference. Replacing the cooler with a new one fixed it. The new engine, with more friction while breaking in, made more heat than the old cooler could handle. I think the coolers get a layer of varnish in them that insulates the hot oil from the metal, and heat transfer is greatly reduced. In the 172, the cooler also lays sideways and its inlet and outlet are halfway up, leaving old oil in the bottom even if the cooler is drained as Cessna recommends, and sludge piles up in there. Flushing doesn't get it all.

The Vernatherm can be tested in boiling water. It should get, IIRC, about a quarter-inch longer when hot.

Old oil hoses fall apart inside. Bits of rubber peel off and block the lines. Bad news. Removing/installing old hoses flexes them and aggravates the problem.

Dan
 
OK. We boiled the sensor and it was fine... we blew out the oil cooler and today we are replacing the Falcon gauge/sensor w/ a Mitchell - Test flight tomorrow! Hopefully I can take her home Saturday.
 
Jeanie said:
OK. We boiled the sensor and it was fine... we blew out the oil cooler and today we are replacing the Falcon gauge/sensor w/ a Mitchell - Test flight tomorrow! Hopefully I can take her home Saturday.
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Unfortunately "blowing out" the cooler won't fix the problem. The oil cooler needs to be sent off to a shop that can completely overhaul the unit. The insides have coked up and without opening the unit and putting it through an acid bath the coking will remain.
 
Rotor&Wing said:
Unfortunately "blowing out" the cooler won't fix the problem. The oil cooler needs to be sent off to a shop that can completely overhaul the unit. The insides have coked up and without opening the unit and putting it through an acid bath the coking will remain.
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Agreed.

Pacific oil cooler service is the way to go. Order a rebuilt one, most likely you will get a new one anyway.
 
Thanks, guys, that's definitely the next step. I'll write this afternoon w/ results of today's flights.....
 
Jeanie:

Ignoring the technical aspects, which I leave to others more qualified than I, I do counsel this: DO NOT take final delivery of this airplane until an independent mechanic, loyal only to you, deems it airworthy and proper.
 
Thanks Spike. I completely understand. We flew the plane today in similar conditions and for similar periods of time. The oil temp was fine.... We believe the problem now was the gauge.
Will be flying more tomorrow and probably taking her home.
 
Hi Ya'll, I flew the decathlon home today -180NM in about 1.5 hrs... good flight, no problems, temps all good. The highest the oil got was about 225-230. and then it went back down to 220. ....
So, about 10 more hrs or so and if all conts good and the oil use stabilizes then I'll change it to regular oil and can start back training in acro.
Cheers,
J
 
Jeanie said:
Hi Ya'll, I flew the decathlon home today -180NM in about 1.5 hrs... good flight, no problems, temps all good. The highest the oil got was about 225-230. and then it went back down to 220. ....
So, about 10 more hrs or so and if all conts good and the oil use stabilizes then I'll change it to regular oil and can start back training in acro.
Cheers,
J
Click to expand...

Better get another oil cooler, that's high oil temp for that engine. You should be seeing about 190-200.
 
Just a data point.

I've been monitoring the new experimental oil cooler I installed following the overhaul on the IO-540. It's basically a standard cooler with a slightly denser cooling fin arrangement. I've observed 185F with an OAT of 75F and 195F with an OAT of 86F. These are at altitude (3-8000') and max cruise (75% or WOT around 150kts) using straight mineral oil. The vernatherm valve on the engine appears to be modulating correctly. At one point just after engine overhaul I varied the oil pressure by adjusting the compression on the oil relief valve spring and noticed oil temperatures increased with higher engine oil pressure. If the oil pressure is set too high the vernatherm valve will not close completely. If it does not close completely oil will bypass the cooler.

Also the CHT's on my engine stabilized around 315F-330F after 20 minutes on the first 30 minute ground run following overhaul using straight mineral oil. I'm now on my first oil change using ashless dispersant oil. The highest CHT I've seen since then is 350F on the hottest cylinder during the first few minutes of a sustained WOT climb to 9000' (this morning). At ground level the OAT was 73F and at 9000' was 62F (it was a sunrise t/o). Mixture was adjusted during the climb for best power.
 
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