Onan Woes

[Confused99 2]

I will start off by saying my 520H is the best tractor I have ever owned. Extremely good workhorse with plenty of power. Mine currently has 1415 hours and running strong....until last Sunday. I was tilling a pretty good size lot. The temps were in the upper 80's with very high humidity so it felt very warm out. Around an hour and a half into it, I was turning in to make another pass and a not so nice noise came from the engine and a light shot of smoke. It sounded exactly like a coffee can with a few nuts and bolts in it shook up for a second. It continued to do the every other second or so for a few moments until I shut it down. I opened the hood and did not find anything abnormal. The oil level was spot on too. I started it back up with the same results, noise every few seconds. I headed straight for the trailer and loaded her up. I looked again and didn't find anything. It did smell very very hot but it was pretty hot that day too. Took it home and left it on the trailer until Monday morning. Went out and fired her up. Started normal with no noise. Ran it for a few min with no noise. Switched out the tiller for the mowing deck, mowed with it for 5-10 min and still no noise. I still have yet to replicate the problem I had on Sunday which is driving me crazy. I have to have this tractor as reliable as possible as I do tilling and mowing with it on the side. And as luck would have it, the back up tractor (the Raider 12) is out of commission with a broken axle snap ring. Also, I cleaned the grass out of the engine last fall and have done around 10 hours of mowing with it since. I wouldn't think that would be enough to pack it full. I also have the gaskets to adjust the valves and decarbon the heads since I figured it was more than due and did have some slight valve ticking since I have been using it (25 hours or so). Anyone else have a similar problem with their Onan. I need to figure it out or I will be forced to buy another and have called on a couple today. Is it possible it is not coming from the engine at all? PTO?

Thanks in advance

Jason

[Confused99 2]

Well, I threw caution to the wind and decided to mow my lawn. It only takes around 45 min so it was a good test. It ran good with no issues but I thought I could hear a knock coming from the engine toward the end. It could also be that I was listening a little more . When I got done I parked it and grabbed the temp gun and took some readings

Oil filter - 235 degrees

Front cylinder just below the intake manifold - 275 degrees

Rear cylinder just below the intake manifold - 295 degrees

Hydro (not that I think there is a problem with it) - 135 degrees

The weather again today is humid and in the upper 80's with the sun out. I don't know what the temps should be but these seem hot especially the oil temp and rear cylinder temp.

Any input is appreciated.

Thanks,

Jason

[Operator 7]

I got nervous there for a minute ! Thought it was neihbor guy"s.

Seems very hot! But they do have a high heat sensor and will shut down.

I was thinking PTO, does it change any in or out?

Randy

[Confused99 2]

LOL...no, his is still good although he has yet to probably put more than a few hours on it. He has been using a C-175 to mow with but sold that last week so the 520H he got from you will start getting some hours.

It does seem hot to me but I do understand air cooled engines normally run hotter than water cooled. I just have no idea how hot they generally get.

PTO in or out didn't seem to make a difference when I was tilling. The noise started when I had the PTO engaged and it was disengaged when I drove it to the trailer. As far as the knock I "though" I heard today, it was more apparent with the PTO engaged but still there when it wasn't.

I am thinking I am going to buy another I found. I will call again in the morning and see if he still has it. As luck would have it, an hour after I called, a guy stopped by the dealership and said he would buy it. If he didn't, I will pick it up.

[Confused99 2]

Wow, 62 views and no other input

I pulled the trigger on another tractor although it isn't red and doesn't burn gas . Picking it up this weekend.

[papaglide 541]

Before I sold mine a few weeks ago, a similiar thing happened. I cut the grass for about 20 minutes or so, turned off the PTO and heard a metal on metal grinding sound eminating from the engine compartment. It was LOUD. Could been nuts in a coffee can sound maybe. I engaged the PTO and it went away. I never found out what it was.

I then sold the tractor.

[Docwheelhorse 2,561]

This is a complete shot in the dark and would be a complete freak if it ---fixed--- itself. But the rattling bolts in a coffee can noise makes me think either it was spark knocking to beat the band because it was so hot OR it tossed an exhaust valve seat and it was clanging around----then only by pure luck it reseated itself and when the engine cooled off it stayed put. I know that sounds crazy.... but the Onan 20's are known for tossing the seats and I don't know but 295 on the rear barrel sounds awful hot.

Tony

[dieselhorse 0]

sounds like she is running lean and might have tossed a valve seat. I would say its time to pull both heads, decarbon and adjust valves and check the valve seats. Onan does offer an oversize replacement valve seat to fix one that has come out, as long as it hasnt beat the block to pieces. We have a 520 at the shop that I think has valve seats out on both cylinders. I plan to talk to the owner when and if he ever comes picks it up. Came in for a charging system issue but she wont start unless you spray some starter juice down the intake. Engine has lots of compression blowing back up thru the carb throat when cranking. But once running it runs and sounds decent. Compression is poor at 60 on the rear bore and 80 on the front bore, but she doesnt burn oil or blow vapor up the valve breather tube. So my guess is valve seat issues. Owner doesnt want to pay the labor costs to tear into the motor. Maybe I can get the tractor on the cheap side. Good luck with your Onan. Mike

[Confused99 2]

I would probably agree that I need to pull the heads and check out the seats. I know they are a problem on the 20 Onan's. I suppose it is possible it did come loose and reseat it self after the engine cooled down. I didn't notice any miss from the engine when the sound came and went and the smoke the first time might have been in my head. Speaking of the PTO though, I did just remove it the day before. I put some grease in the bearing and re-adjusted the brake which I am pretty sure is still off. If I end up finding the problem I might keep it. Otherwise, she is getting parted out which will be a sad day for me as I have become quite attached to her. I hope to tear into her this week.

As for the other tractor, I picked it up and brought her home. It is a John Deere 332 with the Yanmar diesel. So far so good but she needs a good going over and some misc parts replaced. I will do that on Tuesday and put her to work Wed if it doesn't rain.

Jason

[baerpath 517]

Before I sold mine a few weeks ago, a similiar thing happened. I cut the grass for about 20 minutes or so, turned off the PTO and heard a metal on metal grinding sound eminating from the engine compartment. It was LOUD. Could been nuts in a coffee can sound maybe. I engaged the PTO and it went away. I never found out what it was.

I then sold the tractor.

I bought Mikes, Onan It started right up with no noise but I haven't used it other than driving it into the garage. Maybe by next weekend I'll try to mow with it and see if after warming it up it starts making noise. Either way it's getting a Kohler on it

Onans

Duane

[truckin88 104]

onan's after 1000 hours are known for seat issues.

[Confused99 2]

onan's after 1000 hours are known for seat issues.

I was thinking it happened to Onans with almost any amount of hours. I have one out back that I have yet to get into and am pretty sure it has a bad seat. Only runs on one cylinder but every once and a while it will fire on both for a second.

[wedgeheaded 0]

I've seen cars do the same thing when a big chunk of carbon breaks loose. Makes an awful racket then heals it's self as it gets broken up and dispelled. Just a thought.

[Confused99 2]

I've seen cars do the same thing when a big chunk of carbon breaks loose. Makes an awful racket then heals it's self as it gets broken up and dispelled. Just a thought.

Good idea. So far it has given me no problems since.

[Operator 7]

Good to see you still have it. I did think of something, how about the starter drive? "Bendix" maybe? How does it sound when starting/cranking over.

Randy

[Confused99 2]

Good to see you still have it. I did think of something, how about the starter drive? "Bendix" maybe? How does it sound when starting/cranking over.

Randy

I thought it might be that too especially since it hasn't come back after putting a few hours on it. The starter seems to be the same as always but definately has a different sound to it. I will have to check the neighbors 520 to see what his sounds like.