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Engine ran without cover on Onan 15JC


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  #1  
Old 03-18-2017, 11:57:21 AM
bowser22 bowser22 is offline
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Default Engine ran without cover on Onan 15JC

hi guys been a while. Recently had a power outage with all the wind we got on the east coast. I started the 15jc up and let her purr to get to warming temp, somehow the engine cover loosened its way off. Luckily I was in the garage at time moving things into cold storage and noticed the engine rpms take a cut after about 4 minutes of running. I quickly shut the unit off, reinstalled the cover and started her back up. It seems to be working great but just wonder how long these can really run before damage occurs? It was not under any load, I hadn't gotten around to flip the main breaker.
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Old 03-18-2017, 12:05:05 PM
Vanman Vanman is offline
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Default Re: Engine ran without cover on 15JC

If the RPM dropped without a load, sounds like it was thinking about seizing up. Good thing you caught it right away.

From what I understand, with overheating, a few things might happen. For one, the rings can loose their temper, or expand until their gaps close, and then break and / or gall the cylinder. Or the piston can expand and gall the cylinder. In severe cases the piston can be broken.

In your case, it sounds like maybe it was just starting to get tight when you caught it.

In all cases except those with obvious damage, I'd just pay attention to how it runs once cooling is restored, monitoring performance and oil consumption. I'd guess that in most cases they'll end up being fine.

Keith
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Old 03-18-2017, 12:13:28 PM
len k len k is offline
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Default Re: Engine ran without cover on 15JC

Since it was starting to drop rpm things were starting to get tight, so damage was beginning. But you may have caught it in time. Could pull the heads and see what cylinder walls look like.
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Old 03-18-2017, 12:18:04 PM
bowser22 bowser22 is offline
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Default Re: Engine ran without cover on 15JC

I might get a borescope and put it down the plug hole, see what things look like.
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Old 03-18-2017, 12:19:45 PM
Wayne 440 Wayne 440 is offline
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Default Re: Engine ran without cover on 15JC

IF it were mine, I would secure all the covers well, check the lube oil level and run long enough to get the oil hot. Then change oil and filter, and run it loaded for a while.

If no unusual oil consumption or noises, I would say " what good luck..." and not worry about it.
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Old 03-18-2017, 01:11:49 PM
JohnnyC JohnnyC is offline
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Default Re: Engine ran without cover on 15JC

Change your oil and filter now.

JohnnyC
New Jersey

---------- Post added at 01:11:49 PM ---------- Previous post was at 12:45:49 PM ----------

Quote:
Originally Posted by JohnnyC View Post
Change your oil and filter now.

JohnnyC
New Jersey
In addition, I would not go through the extreme of pulling off heads if the JC seems to run ok otherwise you will be spending lots of time and costs for head gaskets, push rod tube O-rings, readjusting valves, yada, yada, yada.... What I would do aside from an oil and filter change is a compression test. A compression test should take no more than 5 minutes a cylinder and is simple. If all seems up to spec and after an oil change, I would just watch for any abnormailites on your next generator exercise under load such as excessive oil consumption.

JohnnyC
New Jersey
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Old 03-18-2017, 01:13:48 PM
len k len k is offline
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Default Re: Engine ran without cover on 15JC

I was just thinking if you saw minor damage to cylinder, you might hone or sandpaper it a little. Hate to spend real money.
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Old 03-18-2017, 01:16:15 PM
bowser22 bowser22 is offline
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Default Re: Engine ran without cover on Onan 15JC

I did pull the dip stick when this happened and it wasn't excessively hot, the oil didn't seem to be burning. It was also around 30 degrees F outside. This engine had milkshake oil in it, which I already dumped out in favor of some cheap stuff. I guess I'll put some of the rotella I've been saving for it.
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Old 03-18-2017, 01:24:08 PM
JohnnyC JohnnyC is offline
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Default Re: Engine ran without cover on Onan 15JC

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Originally Posted by bowser22 View Post
I did pull the dip stick when this happened and it wasn't excessively hot, the oil didn't seem to be burning. It was also around 30 degrees F outside. This engine had milkshake oil in it, which I already dumped out in favor of some cheap stuff. I guess I'll put some of the rotella I've been saving for it.
Does not matter if you believe the oil was not too hot or cold in the pan. IF the engine overheated causing rpms to drop with the *assumption* it was about to seize, change the oil and filter now. There could be microscopic metal debris in the oil from the result of the possible overheating in the cylinder / piston area of the motor.

Do a compression test too as I already mentioned. If compression is low, there may be damage to the rings and /or head gasket as well as head warpage then take it from there. Again, do the easy simple tests first before ripping the entire JC apart without really knowing what is good and bad.

JohnnyC
New Jersey
JohnnyC
New Jersey

Last edited by JohnnyC; 03-18-2017 at 11:46:25 PM.
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Old 03-18-2017, 01:54:22 PM
Vanman Vanman is offline
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Default Re: Engine ran without cover on Onan 15JC

Even if the compression is low immediately following the incident, it is also possible that it will just wear in again. Changing the oil and filter is an excellent plan. Beyond that I would do absolutely nothing besides observation. Run it.

Keith
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