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Ohhh [email protected] I think I blew my engine

14066 Views 48 Replies 11 Participants Last post by  mikebramel
Was plowing the garden with my '78 446. Everything was going good until the very end..... After plowing, I was running the tractor down the road to throw off some of the mud. Right before I turned back into my driveway, I heard a CLUNK and lost most of the power to the engine. It was still running, but not enough power to move the tractor up my inclined drive. It finally died and I can't get it to start again. It's too late tonight to tear into it, but I fear the worst :sad:
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Lived a good life.
Helped many a great deal.
Internal complications.
you forgot about DR. Boomer (smile)
he may be able to do a transplant.
or a by/pass.
thank you. boomer
Oh, no, the dreaded B21.5
Hate to hear that, but hopefully no serious damage to the crank or cylinder bore. Best of luck, and better than luck, we've got Boomer here on this forum. :thumbup:
OK. I'm fairly new to this forum, and I dont' know who Boomer is, but if he has the knowledge that I have seen from Tom A. on other forums, then I am in good hands. I probably won't start on this until the weekend or after, but I am sure that I will have lots of questions once I do.

I'm truly sorry to hear of your recent loss.

Most likely.... a snapped con rod due to occasional lack of lubrication. It happens.

As for that Boomer character.............

Know this....

If Tom A. was in the process of redoing a Onan, then he would be consulting with Boomer on how best to go about it.

If you check the members list, you will see that I personally invited Boomer, along with a few other people who are well-known in the forum community, to fill the first 15 places prior to this site officially going live on the internet. The badge under Boomer's screen name is there because I insisted he have it, not because he asked for it.

Whether you can trust him around your wife or not...that I cannot say. :sidelaugh: :sidelaugh: :sidelaugh:
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Most of us are Old Pharts and the two things that you can't trust with Old Pharts are counting on us to replace the adult beverages that we took from you garage refrigerator and leaving the toilet as clean as we found it!!!! :sidelaugh: :sidelaugh: :goodpost: :drinkbuddies: :mowlawn:
Mad Mackie in Taxonnecticut :cry:
OK, so here is my first analysis.....right cylinder has 60 psi compression, left has 0 psi. (what is the appropriate compression???? 60 seems low.)

Pulled left side head cover and piston does not move while cranking. I can push it in manually, but it doesn't come out. Sounds like bad piston arm??

My question is, is this worth the effort in gettng parts to rebuild? Are parts like this still available? Or am I looking at a replacement engine?

You all probably know this already... but its an Onan B43M, 16 hp. 1978 model 446.

Thanks in advance,
As I said in an earlier post, you have a broken connecting rod. (Piston arm is your terminology)

The engine needs to be removed and carefully dismantled for inspection. Most likely, the block did not suffer major damage and it can be rebuilt. Compression should be 90 PSI or better on both cylinders. Less than that figure indicates substantial wear.

Parts are available and rebuilding the engine is worthwhile. Boomer is the man to talk to and also work with. He will be along shortly.

Yes... it is possible to put a different engine in but when you do that, you run into engine mounting, pump mounting, exhaust, wiring, PTO clutch issues etc that all must be solved. Staying with the engine you have has lots of advantages. It means that when you are done, your tractor is still "stock", just as Case made it. Anyone can look at the parts manual and service manuals to figure out how to repair a problem or purchase the correct worn-out part.
Like mentioned above, the connecting rod has most likely broken and now the piston is left floating in the cylinder wall. Boomer will advise you on what you should do and I'm willing to bet he is going to tell you that a full rebuild is in your future if funds permit. I don't know how deep your pockets are or how much you love your tractor but how would you feel if someone told you that it could cost you around $1,000?
The $1000 figure is what I was afraid of. I don't mind doing the work myself, but I didn't know if finding parts was possible and I am not a fan of ebay. It sounds like I can get parts, I will just have to pay through the nose to get them. I will wait for Boomers input, but I have seen other Case tractors on my local CL that are for sale in the same $1000 range or slightly less. Of course theres also a couple for $3k - $4k, but that is way out of my league.

As for lawn mowing, I have a back-up plan...I borrowed my father's old snapper rear engine rider :oops: I may have to put on a disguise to use it so nobody will recognize me :lol:
You may be able to find a complete used engine in good running shape and just perform a swap. That is how my 77 446 is. It now has Performer 16 engine in it. Boomer may have something for you that will save your wallet a bit too. How mechanically inclined are you to tackle a rebuild yourself on this engine? Do you have the proper tools needed?

Just dont go and give up on the tractor and sell it cheap and then go and buy some big box store mower.
True enough but someone may also tell you that a new replacement engine will cost you more than $1000.00 just to buy it. Then you will have to pay applicable state taxes and shipping to get it to your door.

After that, you will still have to remove your existing Onan.

Then, the fun begins because you need to position this replacement engine correctly so that the electric PTO that must be used, lines up with the mule pulleys for the deck and snowcaster. And then you may have to buy and install a new ignition switch and rewire half of the electrical system after adapting the throttle/choke cables and fuel line. New mounting holes must be drilled in the frame to secure the engine. But the really fun part is in having to fabricate an exhaust system from scratch. This is best done with a Tig Welder.

When you are finished with the conversion, do not expect this tractor to have any trade-in value. Dealers have no interest in accepting modified machinery for a number of very valid reasons. Re-powering should only be done if you intend to personally keep and use the tractor for many years to come. That's the only way you will ever see a return on your investment. However, since electric clutches are not known for long life expectancy, you should put aside money regularly in a "clutch fund" to pay for the next $300.00 clutch when the current one fails.
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at this time you should go to the manuals and download the
service manual for the B43M.
study it.
then remove the engine, remove the oil pan.
remove the broken rod and piston.
there will poss. be alum. on the rod journal.
look for damage inside the block.
damaged oil tube,damaged cyl wall, broken cam etc.
check how much movement up and down on both ends of the crank.
you should barely be able to feel any play.
you may get lucky, and only need a rod and or piston and some gaskets.
start here and get back to us.
good luck. boomer
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Uuuuggghhhh. Man I need that lottery money.

As far as mechanically inclined, I would rate myself above average. (I just put a timing belt in my son's car). I have rewired this beast once (mice chewed through the wires). I've replaced the starter, and I've replaced the components of the EZ adjust clutch. (no electric clutch here). I typically am not afraid to tear into anything..... that's what makes me dangerous. Tools,..... that's another subject. I have the basic hand tools, air compressor, air tools and normal mechanics tools. I don't have a cylinder hone, or special stuff like that. Harbor Freight is my friend. :grin:

I'll start tearing into it and see what I find. It may take me a few days as its too cold in my garage and I have some other things going on. Thanks to all for the initial guidance. to check on pricing

60PSI may just need a valve job and rings
mike and club
i recommend onan to many of my customers.
BUT they are mainly NEW parts (some used)
i,m just the opposite.
if geeco wants a rod, he will have to purchase two of them, (the latest P series rod)
to keep his engine in balance.
onan parts,com explains that, and the fact of different pistons,
at their site.
thank you. boomer

As Boomer said, you have to open it up and figure what what got damaged by that broken rod flailing around. If you are lucky, it broke off just above the crank journal.

No matter what, the entire engine will have to dismantled. You then need to employ the services of a machine shop that is fully experienced with Onan engines. They will check the bores for taper, wear and whether they are oval.

The likelihood of getting away with a fresh set of rings is slim. The engine failed for a very good reason and that most likely was oil starvation or too much carbon deposit in that cylinder. As much as this hurts, the wise thing to do is a proper rebuild instead of a patch up job that may fail on you in short order because you overlooked something. If that happens, then you can kiss goodbye whatever you spent previously plus you will have to re and re the engine once again. Of course, this will happen at the worst possible time which is in the early part of the growing or snow blowing season. That's one of Murphy's Law's.

Keep in mind that these engines spin at 3600 RPM and that translates to 60 times PER SECOND all the time you are blowing snow or cutting grass. If you don't respect that fact, then bad things can happen.

Consult the FAQ's section for the guide on Where to buy STUFF. There are several places to purchase Onan parts and I advise you to shop around once you know exactly what you need. Your machine shop will help you make that list and the parts books will help you with part numbers.

We are here to assist, when needed.
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I'm watching this thread with great interest as I have a P218G that I'm sure has a broken rod as well .
Boomer was kind enough to contact me and tell me about this forum which seems to have some really knowledgable techies on here :thumbsup:
I will be attempting to do my own teardown and repair and I do have a technical background although this is my first Onan I've owned . I purchased this 1987 JD 318 with the understanding it was only running on one cyl but the price was hard to pass up and left room to do the needed repairs to get this machine back in top condition .

Yes , I have a green/yellow machine ( yeah , I know....Booooo! ) but in looking at some of the Case and other machines I've seen I may just end up with at least 1 Case (maybe 2 or 3 ) at some point .

My 1st post here , so hello members and I hope my current GT ownership will not be frowned apon :canada:
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