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john deere 318 help, i think the Onan is done for good?

22844 Views 103 Replies 28 Participants Last post by  alfieepstein
New to this forum, and i must say it looks fantastic! lots of helpful people, and lots of great tractor stuff. I bought my "new" 318 in the fall. My first real garden tractor. I searched for quite some time for a machine that could bag vast amounts of leafs, and clear alot of sloped, fairly steep, slippery driveway, and decided on this 318. came with power blower/catcher for leaves and the auger snowblower. It did a great job with the leaves. I was so excited to plow the driveway on this first winter storm in chicago. Well, i tried plowing without the chains, (1st mistake) and the driveway was too slippery, so i went to go get the chains and while doing that, the engine started sounding different, almost like it was on choke. Well, the engine then quit, and now won't start. The starter seems to want to crank it over, but can't so i get a grinding noise. I fear the worst, a siezed engine. There was oil in it, my only concern is that it was parked on a hill for a while, could the oil have drained back leaving no lubrication? is there an oil pump on these Onan engines? I am fairly mechanical, but haven't dealt with tractors too much. Usually if instructed well i can find the problem. my question now is, where do i start? What can i look for to figure out if this engine is done? I'm assuming that since it started ok that it is nothing electrical, and the snow thrower wasn't on and it was in neutral so i don't think its anything related to those two issues. I'm just praying someone with a good knowledge of these machines has seen this before. I don't really want to have to start the post of "so what's the best repower engine" :banghead3 although i'm pretty sure that that is coming.
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ok, the link takes you to my new snapfish album with a few photos of the cylinder. It's not as good as seeing it in person, but it's something.
Your course of action sort of depends on your budget,and how much you want to do yourself.

The engine needs to come out, that's for sure.

The options I see are these:

replace with a good running used engine.

Tear it down and measure the cylinders and crankshaft. If useable, replace the piston and rod with your used parts. I'd install new rings on both sides after lightly honing.

At the other end of the repair scale is crank turning and/or boring if needed along with the necessary new parts. Starts to get pricy.

You can really tell much until it's laying on your bench in pieces and you have mics or calipers in hand.
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You need to pull the motor!!!!!! First remove the driveshaft.4 bolts hold the motor down.pull the oil pan and you can remove the broken rod.The rods and pistons have to match( see post by glocem on 420) he had mid matched will need a hone for the bore.New rings from onan parts.The motor must have been broken for a while with the water in it.It could not have gotten water in it unless the breather was off and the hood was up.The water could have caused a hydrolic lock and broke the rod?
Oops I see you have engine out.I looked at your first post and that was probably when it broke the rod.
ok, well things have gone from bad to worse. I'm pretty sure im looking at a repower here. Essentially this is what i found.

When i pulled the oil pan i found out it was definantly the rod. The rod was shattered. Essentially what was left of the rod then pushed up and lodged inside the piston head. I managed to get the rod part out of the inside of the piston. I got the piston out and from what i can tell the cylinder looks good. I placed one of the extra piston heads i had in there and it seems to slide in and out OK.

The crankshaft has some slight damage however, i took a picture but i needed to use a flashlight and that led to a poor picture, i hope to take one in the sunlight so its easier to see because that's definantly one thing i want you all to look at. There seems to be some extra metal on the part where the rod connects that is almost fused on. I would obviously need to get that off if i were to put a new rod on. but it looks like there is pretty significant wear. So i guess my other question is how "pristine" does crankshaft need to be where it connects to the rod?

when comparing the old piston head with the extra i have, i noticed that they seem to be the same size, however the ring pattern is different. The spare pistons i have use smaller piston rings. Could these be from a B series? The rods on the spares say Onan, so they are Onan pistons, but i know that the old rings wouldn't fit on there, you can visually tell. I took a picture of that as well. So my question is could i use these pistons if they are the same size and the rod is the same size?

here is the link to the new pics
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You should look here on the second page as that should explain the different series of pistons used in P218. The crank MAY just have some material fused on it from the rod which MAY be able to be polished off. If not, the crank journal will have to be ground down and oversize rod used.
Was the rod still on the crank? post a picture of the rod inside where it attaches to the crank.Dont rule out rebuilding with new rings.Do the rods have the same number?do both your roda have a hole in the rod? the pistons have to match,the rings will have to be the same also.Rings are cheap,pistons are not too high.Like dkarst said you can scrape th aluminum off the crank but it will need to be plastic gaged to assure it still good.
Metal transfer on the crank is a sure sign if insufficient oil. So, the main and cam bearings are also suspect. So, the engine needs to be completely disassembled, cleaned, inspected and measured before you can be sure, with any degree of accuracy, what is needed.

Once the crank is out, I recommend soaking it in a lye (or granular Draino) solution. The lye is dangerous but not nearly as much as an acid to disolve the aluminum. Acid will also etch steel/iron if left on too long. Lye will not. There is also no danger of wearing or scratching the journal as is the case with sanding or scraping. Pour the solution down your drain when done and you get a free drain cleaning!
Hey AMS:
Are you committed to a rebuild? Certainly educational, but definitely time consuming. I decided against a rebuild because I didn't want to spend what would probably turn into a couple of weeks working on my engine, what with the trips to the machine shop and store to buy/rent tools I don't have, etc. Also I figured I'd end up with a rebuilt version of what is an '86 engine: good but 26 years old just the same....
I bit the bullet and spent the extra $$ on a Briggs Vanguard 18hp engine from SEW: $1640 delivered to my door. Installation took some time, but the electronics really are plug and play plus you get a new PTO clutch and a new muffler. The engine uses a lot less gas, burns cleaner, and starts every time.
Of course, your decision depends on your finances, and your mechanical know-how. Certainly, a rebuilt Onan is a very capable engine and I have to give 'props' to everyone who follows through and rebuilds one. I personally would rather spend my time working 'with' my 318 than working 'on' it. Now I just have to do something with my Onan!
Good Luck!
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Get some fedback from BOOMER, or OnanParts,they are the Onan gurus here.I know what I would do but i have lots of time and have more than 1 JD with Onan power.
ok, i will start breaking the entire engine down. I will try and get pictures up of everything and start asking on how to check for damage once it's all apart. Now for a couple more questions.

1. If it was lack of oil was it because it was sitting for 10 minutes or so running on a slight incline? it was on the driveway which has a slant, but not an outrageously big slant. Also there are some hills on the property so it does spend some time on hills. When i checked the oil it seemed fine, and the oil light never came on. (maybe a bad sensor or burnt bulb?) Or is it possible this damage was caused by the previous owner and it just reared its ugly head now?

2. I found a guy selling 2 pistons and a crankshaft for a P218 engine. Said he repowered and is parting out the Onan. (first off how big of a risk is it buying it?) 2nd, If I am replacing all 3 components will it be compatible with my P218? If there is a possibility it won't be, what information do i need to get to make sure it would be compatible?

3. finally after posting 1 and 2. I read the link about rebuilding from Onan parts, and its amazing. Makes me feel like i can do it. I think at the very least i will break it down and see what damage is in there. Finally, after reading that it looks like if that setup measures out ok it would work since all the parts are the same style. Now my question is if i have to machine the cylinders, does that mean i would need larger pistons? or do i just need larger rings?
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I think the crank damage was old.The rods are designed to break at the hole saving the block from damage.If it needs bored larger pistons would be required BUT the bore will probably fine.The slope should not hurt the motor.The p218 will work.Same motor just different ignition
Before buying anything you may not need, you really need to take things apart (slowly) and see what you have. If you're really lucky, maybe you can get the crank journal cleaned up and measured, buy two new rods (they need to match, or maybe old matching rod if you trust seller), stick some new rings on pistons assuming ring grooves are okay, get a finish hone put on the cylinders assuming they measure within spec for size and are not too "egg" shaped, and put things back together. Just depends on how your karma is...
Well i have taken some time trying to get the engine apart. I think I am going to just repower. Here's the update.

1. I got the PTO off ok, but im having trouble getting the flywheel off. Is it pressed on? do i need some type of puller or am i just being too kind to it?

2. I'm having trouble getting the good piston out. It's catching on the first ring. I didn't want to start banging on stuff in there. What's the best way to get that out?

3. The crankshaft doesn't look good. seems like significant wear on the side with the bad rod compared to the other side. Also there are some gouges and marks on various parts of it presumably from parts hitting it while moving. But to me that journal on the blown side looks pretty bad.

4. I don't think that i have the expertise necessary to rebuild myself. I'm having more trouble than i thought taking it apart. (appearantly this engine isn't as easy as the 3.5 hp briggs and stratton i took apart and rebuilt in shop class 10 years ago :) )And putting together is a much tougher deal. I worry about damaging parts and making a bigger mess as i go along. I think I am just going to bite the bullet and have a nice new engine. I however, might try to rebuild this one just for the expierience and entertainment in the mean time. If not it will just be parted out to the best of my ability with the stuff i know is good.

4. Thank you all so much for your help. You might see continuing posts as i try to rebuild anyway ( will depend upon how bores and other parts are mostly. Don't mind taking the time but i won't want to spend a ton of money on an engine i probably won't use)

5. Finally, my last questions are on the repowers. I read some other posts on repowers, but am looking for a bit of fresh insight. I've done some research and I am 95% sure im going with the Vanguard. Probably the 23 hp. Figure if im putting in a new engine, what's a few hundred more bucks for a bigger one? My question is this.....

Anybody have any experience with the Vanguards? like them? hate them? Any recommendations on the big 3 replacement engines?

Also, what is in the adapter kits? How much does it take to get the Vanguard (or other engines) in place correctly? Are they parts i could fabricate myself? (mainly just brackets) or are we talking new driveshafts and things of that nature? It seems like quite a bit gets tacked on to the price when an adapter kit is included. Anybody who has repowered i would love your advice and reviews!
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As long as your in " what's a few hundred bucks " mood- why not find a 420/430 transaxle with 2 spd and diff lock. ?

With the 23HP that would make an awesome 318 !
Oh man it's painful to watch all these old Onans die a slow death but to be honest it's time has come and gone.

Parts are entirely to expensive now to even consider trying to fix them. I hate to say it but the best bet is a repower with a Kohler, Kawasaki or Vanguard and without a doubt the Vanguard has proven itself to be one he$$ of a good engine.

Out of all the repower threads I see the Vanguard always gets high marks in reliability and performance.

RIP Onan :sorry1:
@ Leinie:

Lol, i will keep that in mind and start watching craigslist. Although i probably won't replace until i need too. If i do that I am also gonna have to find some decals that say "robotractor" or "i used to be a john deere 318" :)
Hi there ams4life. If you are considering an "un-pure" 318 and don't want to spend the $1500 on a new Vangard or Kohler, try looking at some of the Chinese engines, even diesels.
For $800 you can get a 20HP Honda GX670 twin photocopy good for 1000 hours with proper maintenance. I have a friend in the tool and equipment rental business and he regularly replaces engines (Onan, Kohler , Briggs etc) with Aisan imports with good results. Its all about " bang for the buck". The main concerns are shaft size and rotation. Your P218has a 1.125" shaft and clockwise (facing the shaft end) rotation. Fitting a tall V-twin in the space of the flat boxer style Onan may involve some work too. I know lots of 318 have been re-powered with current engines but I have no personal experience - Google the subject and I'm sure you'll get more info. Look here -
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I am more-or-less in the same boat with a 318 I bought for $250 knowing it needed work. My B43G runs, but poorly. It will only run on full throttle and it has low compression (70 psi) on both cylinders. Like Ams4life, I am hoping to get away with rings and a few other parts and have a nice running engine. Fortunately, we have the good fortune to be able to find out what is needed before we buy anything, other than investing a little at the machine shop, which is worth the gamble.

In my case, I plan to weigh the rebuild price tag with a Vanguard repower once all is known and decide from there. After all, my engine has got to have some value, since it is still running, and if I need to part it out or sell it as a core, it can offset the repower. Best of all, the LOML is on board, mainly because when the 318 gets useful, I can sell my 165, which is a great tractor that's runing like a deer.

Here's a pic of the 318 with her new seat...

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Oh man it's painful to watch all these old Onans die a slow death but to be honest it's time has come and gone.
marcuskelley35 sure has that right! There are no modern small engines manufactured anymore with the high quality of an Onan.

The picture here is just one example comparing the Onan to a "modern" Kohler V-twin.

The first thing you notice is that nice big 100% iron & steel oil pump used by Onan for over 50 years. Note the pickup is also made of steel. The Kohler oil pump is made of aluminum with a PLASTIC drive gear! Even the pickup is PLASTIC. :(

Can you find the cam & main bearings for the Kohler?....Look closer...that's right! The crankcase is the bearing! Run it low on oil or just normal wear and you toss out the "disposable" modern kohler V-twin. Go buy another one. Kohler made it to be replaced not rebuilt.

Just above the Onan oil pump is a "replaceable" Onan main bearing. Cam bearings are also replaceable in the Onan's. Break or damage the oil filter mount on the Kohler and you are looking at replacing the entire engine cover, not cheap! Plus the fact you have to take the engine half way apart to do it!

The Onan filter mount? Two bolts and an easy swap.

I'll start a new thread soon comparing the Onan, Honda, B&S, Kohler etc. internal engine parts.

For some folks repower is the only way to go if you don't have the time, tools, skills etc. to rebuild your Onan. Just don't expect a "modern" engine to have the same quality as an industrial Onan or last as long. It won't. Facts are facts and the cold hard truth is nothing is made to last anymore.

The good news for those who choose to keep their Onan's going is that new replacement parts are still made right here in the U.S of A! Just need a good deal on some used parts? Millions of Onan's were made so finding used parts in good shape is easy. :)


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