520H major oil leak

[Theroundhousernr 589]

Ok so i bought a 520h. I believe its an 89 or 90. That stated ,it leaked major oil and motor was not usable the way it was. Needed a rebuild said the add. So I went to look at it anyway and took it home with me. The tractor is a one owner tractor and used to cut grass only. Apparently , the husband got sick and was in the hospital leaving the wife to mow lawn. She noticed the oil leaking and parked it. The OP just picked up a zero turn and did not want to use the 520 anymore. It had been garage kept all its life and was just parked outside last fall to make room for the zero turn.

 

  So I get it home and first off I noticed it was way overful with oil. The OP did this i believe so he could start it for people and drive it up on the trailor. When he started it for me , the motor ran perfect with no knocks or unsual noise and idle + revved just fine. The tractor has 1000 hours on it.  

 

  It leaks about a pint every 10 mins ! lots of oil. The first thing I see is the bearing plate behind the pto is so loose I could move the bolts with my fingers. You could actually see it vibrating around the bolt holes while running.

 

   My plan is to change oil and put the proper amount in it and tighten down the bearing plate to see if that stops the oil from leaking. If it does thats great but there is some oil leaking on the flywheel side also....

 

   So my question are. Could any damage have been done with the bearing plate being loose? The bolts where not hanging off or anything. They where only just finger tight.

 

  Second question is , could the flywheel side  be leaking because of it being so darn overful or is there something thats common on the Onan's that causes leaking of oil on the flywheel side? I will hopefully get to play with it a little tonight and see.

 

    Thanks in advanced for your input, Kyle

Edited March 19, 2014 by Theroundhousernr

[jimt1971 236]

Kyle,

I saw that on Craigslist. That was a great deal. Could just be the loose bearing plate. Good Luck with it.

Jim

[WH nut 553]

I suppose it could have cracked the plate due to vibration, But Im a gambler. Tighten it down and see what you have.

[Jim_M 178]

There's a welch plug behind the flywheel that has been known to leak. There's also a crankshaft seal behind the flywheel that could possibly leak.

Edited March 19, 2014 by Jim_M

[Ed Kennell 36,035]

Hi Kyle,  I just got a 1988 520H and am in the process of redoing the engine.  It had a major oil leak on the flywheel side that had all the cooling fins packed with oil and dirt on the rear cylinder. The oil leak was between the oil filter bracket and the block. You will have to remove the tin  to access the two bolts in the bracket.

  You may want to look at my post in the tractor forum  titled   .......New ?..Find .

[Desko 552]

The oil leak could be the fuel pump pulse line on the timing cover(note: not all onans have the line on the timing cover some were on the block) so check that also the line may be damaged or off also causing oil leaks. Also check your PVC valve (Line from valve cover or block into air cleaner.

[stevebo-(Moderator) 8,059]

Over the weekend I decided to change the oil and filter in my 520HC. I could not get the oil filter off so I decided to drive a screwdriver through the side and used that as leverage to turn it. That worked but...... I cracked the filter housing. When I went to remove it I found that the two bolts holding it into the block were loose. I think you may want to take a look at that as well to ensure that it is tight. There is a gasket between the housing and the block.

[Theroundhousernr 589]

Tightening the bearing plate tonight and looking for stress cracks anywhere. Seems to be ok. Not sure if i can tear into the flywheel side tonight. It's getting late. The rear cylinder is caked with grease and oil. Got to get that clean before major use of any kind.

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[Ed Kennell 36,035]

Hi Kyle,  I just got a 1988 520H and am in the process of redoing the engine.  It had a major oil leak on the flywheel side that had all the cooling fins packed with oil and dirt on the rear cylinder. The oil leak was between the oil filter bracket and the block. You will have to remove the tin  to access the two bolts in the bracket.

  You may want to look at my post in the tractor forum  titled   .......New ?..Find .

 

Over the weekend I decided to change the oil and filter in my 520HC. I could not get the oil filter off so I decided to drive a screwdriver through the side and used that as leverage to turn it. That worked but...... I cracked the filter housing. When I went to remove it I found that the two bolts holding it into the block were loose. I think you may want to take a look at that as well to ensure that it is tight. There is a gasket between the housing and the block.

More evidence this oil filter base is a likely place for an oil leak as suggested by GMAN on my " New ? Find"  thread.   He was correct, this was the source of my leak. The bottom bolt was loose. GMAN recommended replacing the gasket and loctiting the two bolts.  I will do this on mine.

[Theroundhousernr 589]

Ok guys, I pushed through the wee hours of the night. All sheilds are off the motor now, including fly wheel shroud. What an adventure working on an onan. Ten pounds of s*** in a five pound bag. I took everyone suggestions and come up with nothing lol. The oil filter bracket was tight, the oil pulse line was in great shape. However my tins are just as caked as ekennells where.

 

  My plan moving forward is this. There is to much crap smered every to come up with an answer as to where this stuff is coming from. I still dont know the condition of the motor as I have only been able to run it a few minutes. It ran beautiful when I did have it running. So its not ideal but my only choice. I have to clean and strip the motor of all this garbage and get her hot and run it awhile to get more answers. I dont wont to spend money and time on a motor that is heading for the machine shop.

 

  Everything is soaking tonight with a spray on gum cutter. I removed the starter and plugged all oil lines and holes to the motor. I will cover up all electrical I can and shoot it with the pressure washer tomorrow after work. Then I will reassemble the motor and run it and check for leaks. I feel the motor was overfull causing it to push out the seals. Some could also be from changing the filter/ filter working loose at one time or maybe the gasket between the oil filter housing and block is bad but not able to tell at this moment. We will see I guess.

 

  Fingers crossed , what do you gentlemen think?

[Theroundhousernr 589]

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[Martin 2,130]

if the motor was over full, check around the bottom of the gear case cover (cover behind flywheel) when you get it cleaned up. the oil level when full is close to this area normally, so it would be 'underwater' when over full.

that and the other suggestions are common leak points on these engines. the loose bearing plate is a concern to me as well. that could have allowed some small movement along the crank line, so check your seals well too. i just hope you didn't have much up and down movement as the bearings could be of concern.

i would be careful pressure washing around that area as well, you have an ignition pickup sensor behind the flywheel and they run $80+ new. not sure how water friendly they are, but I'm always real careful with that aminal, 

if i were you i would keep the water away and just pull the flywheel and anything else big that is in the way and get a couple rolls of shop towels and a scraper and clean it up. just until you know whether you have any bad gaskets, seals etc. you don't want to introduce a bunch of water inside that engine. brake cleaner through a straw is also a good localized cleaner and will loosen some of the stubborn stuff.

 

also be careful on the 'overfull'. one of my p216 Onans is always half way up the dipstick when pulling the dipstick when cold. the wipe and recheck shows right at the full line. just an fyi.

[Ed Kennell 36,035]

You are right Kyle....compared to the Kohlers, it's no fun working on the Onan. The location of all the crud in both our engines  really points to that oil filter area. While you have all the tin off, I would  still remove the filter and base bracket  and reseal the bracket.  If this is were the leak is, I don't think you would be able to see it with the engine assembled. The air flow will blow the oil across the bottom of the back cylinder and deposit it on the lower tin again where you can't see it.

 

 Don't give up ... We can save these tractors !

[Theroundhousernr 589]

Well, I'm not thrilled about using the pressure washer either. I'm on a time restraint. My significant other wants her basement remodel finished and i need the garage space. I will admit I wasn't going for a complete proper fix just yet. I want to get it to stop leaking oil all over when i move it and make sure i have a good motor before dumping money in gaskets and what not. I think most of the major oil leak was from the pto side. I think the flywheel side had been a long slow going leak.

My other issue is I don't have a proper flywheel puller for this engine. I agree that this thing would not like water. It's built like a car engine.

A good friend of mine owns a 520 and warned me of the dip stick reading. Lucky for me that I'm OCD , and check the dipstick 3 or four times till i get consistent reading on any motor. Thanks for pointing that out though. It is important to know.

I have virtually no lateral play in the crankshaft. I had a few thousand more end play then i cared for but when i tightened the bearing plate. It went away. I got really lucky i think. The Op was smart enough not to use it when this condition occurred.

Any of you guys think of a quick way of degreasing this thing?

PS, I do plan on opening it back up and replacing gaskets ,cleaning the heads and checking valve clearance before putting it into service. Just need to get it buttoned up enough to run and drive a little.

Thanks

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[Martin 2,130]

Brake clean is your quickest and easiest way, not good on painted areas though.....

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[Ed Kennell 36,035]

                                               On sale @ NAPA for  $2.19.

 

       Kyle, Another potential leak is the oil drain pipe.  Mine was also loose, and the 90 deg ell will not allow you to tighten them without removing the engine .

       I cut mine off to get it out and replaced it with a straight 4" nipple and cap. Now I can tighten it any time. Just need to make a foil trough when draining the oil... I usually do this anyway.

 

                                                 New drain                 

                                                 Filter bracket            

[Theroundhousernr 589]

Here is my new revised plan. I guess instead of getting excited and rushing things. Im going to pull the engine. I am only a few bolts away from that point anyway. Get it up on the bench, put a tray under it to catch liquids and go to town. I will be able to reach everything better and see alot better whats going on. I bought a few bottle brushes today and more brake cleaner. So I will give you guys an update when I get there . Thanks for the photos Ed. You have yours a little more clean then mine already and I am able to see better what Im looking at. Thanks to everyone else alos.

   Kyle

Edited March 20, 2014 by Theroundhousernr

[leeave96 487]

Here is my new revised plan. I guess instead of getting excited and rushing things. Im going to pull the engine. I am only a few bolts away from that point anyway. Get it up on the bench, put a tray under it to catch liquids and go to town. I will be able to reach everything better and see alot better whats going on. I bought a few bottle brushes today and more brake cleaner. So I will give you guys an update when I get there . Thanks for the photos Ed. You have yours a little more clean then mine already and I am able to see better what Im looking at. Thanks to everyone else alos.

   Kyle

 

While your there, you might think about de-carbing the heads and resetting the valve clearances too.  Maybe some others can chime-in on what would be easy to do maintenance while the engine is out.

 

Just curious - any problems getting the tin off?  Did you snap any screws?  I have the worse luck when trying to remove engine tins from an aluminum block engine and dread the day it comes with my Onans.

 

Good luck,

Bill

[Theroundhousernr 589]

   I should be knocking on wood but everything came off with ease. I think it has to do with this thing being stored indoors all its life and soaked with grease and oil. I mean everything came off smooth with no issues. You have to treat bolts in aluminum a little different. I like to use a wrench or ratchet and tap with a hammer on the end of the wrench. A quick light shock seems to pop them loose everytime. I had a little trouble with getting the bolts out of the pulley for the pto. They came out pretty tough and they had lock tight on them. I was worried about stapping those puppys. When reinserting them, chase the threads and a little never seize goes a long way down the road.  

 

  Simply put. I just don't have the time right now to go over the valves and head. I dont have the gaskets either. I should have never pulled it in the garage but that thing was begging me to look over it everytime I walked by lol. And like mentioned before. Why spend time on this thing if I have fruther damage? I need to get her running the way it is first.

[ericj 1,576]

i just bought a 518H that upon getting it running had a bad oil leak in the oil filter area. so i decided to change the oil and low and behold the filter was loose after oil and filter change no more oil leak, now i have to pull engine tins and clean. i was able to reach in around the filter area and pull hands full of sludge out. so i know it's bad.

 

 

 

eric j 

[Theroundhousernr 589]

Well I did some cleaning on the 520. The heavy grease is gone. Just need to do the final cleaning to make it shine.

It's funny you mention that Eric. I couldn't find the leak in the fly wheel side so I had my fellow wheel horse nut stop by. He saw a problem right away. The oil filter was the wrong one and not sealing on the housing. He ran home and got one for me. The filter he use is a little taller than the original but the same circumference. I'll post a picture so you guys can see the difference. It's evident that the leak on the flywheel side had been there a long time. I wonder how long the OP was using the wrong filter.

Here is the tractor ready to roll outside to get washed for the final assembly.

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[ericj 1,576]

my 518 had an onan filter on it just not tight

 

 

eric j

[Theroundhousernr 589]

I just thought it was interesting. The smaller filters barely makes contact with the inner sealing surface of the housing. It's tight though. Hopefully tomorrow I can get her running and hopefully have a good block to work with. Then I'll check heads, valves and reseal intake gaskets.

If not, later in the spring/ summer you will be seeing an onan rebuild thread lol.

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[Theroundhousernr 589]

Update. She is back together. She fired right up and NO leaks    . So the crank brearing plate was loose and all I did was tighten it down. It also had the wrong size oil filter. I even went and bought a crank seal and bearing plate gasket today thinking I could not get that lucky. It does not leak a drop!  Now I am left with a tiny little miss. I drained the old gas and put fresh gas in it today. Hopefully some running will fix the problem. If not , I will be opening her up anyway for a good tune up and clean up. I just don't have the time for a least a few weeks till my remodel is done for all that work.

 

    Thanks everyone

Edited March 22, 2014 by Theroundhousernr

[woodchuckfarmer 333]

Glad to hear you got it fixed without to much trouble....Wayne