YM 336 Engine Issue

[darien7]

Hello Everyone,
It has been a while since I last posted. My issue now is I am looking for options to either replacing my engine, rebuilding my existing one or buying a long or short block. I believe cylinder #1 is not firing-(We are getting ready to do a compression check as soon as I can get ahold of a compression guage. Also, this cylinder is one that I've had a previous issue with) I'm pretty sure that it is low. Anyway, just looking for the best least expensive way to get my tractor going again. My engine number is 3T84A-N. I had a competent mechanic stop by to listen to it and give his advise. He believes that if I go with a different engine, it need not be the exact one I am replacing, in that he knows that others have the same bolt up pattern. Anyway, what do full rebuild kits cost or does someone out there have any of the above options I mentioned?

 

[normde2001]

"I believe cylinder #1 is not firing"
Don't get carried away. That is certainly no reason to entertain the idea of replacing, short-blocking, or even rebuilding your engine. There are no short blocks or rebuild kits. With what you know now, the most you might need is an injector rebuild or rings and a sleeve. Find out if the cylinder is firing or not and why.

 

[darien7]

Norm,

About 3 months (or more) ago, I had the head, valves ect redone at a machine shop. While the head was off, we noticed that piston #1 had movement in it so we replaced the bearings, snugged things up (I was trying to go cheap) and ended up replacing the rings since we broke them durring the procedure. We did not replace the sleeve, which I guess could be a problem. I had the injector checked at a reputable place so we covered that base.

 

[kenmac]

If I were going to go as far as replace an engine .I think I would just do a rebuild on mine(if you intend to keep the tractor) at least, you will know what you have. If you buy a used engine & go through all that work & have to do a rebuild on the used engine it in a couple years, what will you have gained ?

Just a thought

 

[dfkrug]

My JD 955s use the Yanmar 3TN84RJ, which must be very similar.
Both clearly have the 84mm piston bores. I rebuilt 3 of these
engines, and the only parts I needed to buy were piston/ring
assemblies and a head gasket. Bearings were still good. I DID
need to pay a shop to bore the block .5mm, the largest you can
go. There are no sleeves.

At the time, I could buy a motor new for $5400, vs the $500 in parts
I needed to do it myself. Motors have not been available from
Deere for at least 2 years now, so that option is prob out for you, too.

 

[lens12]

I all most always recommend rebuilding. You know what you have when you get done. It will probably cost less than a replacement engine. If done right it will be as good as a new engine.

 

[darien7]

Thanks everyone for your thoughts on this. I am encouraged that this should not be such a big deal. It may take a little time to resolve since I am waiting on a friend of a friend to loan me his diesel compression guage. I just want to see the results before I rip the head off again. I will continue to monitor any replies if anyone has anything else to add. Thanks again all.

 

[oliver28472]

If the compression test indicates a problem, a cylinder leakdown test may be the next step. It basically involve pumping air into the cylinder and watching how fast it leaks down on a guage. During leakdown you may be able to listen and locate where the leak is. Ask your mechanic about this.

 

[darien7]

Ok, We took the head off and the rod bearings for #1 were almost gone. Looking at the crankshaft, it looks like it cannot be turned.(It has a significant ridge on it that looks way more than the oversized bearings can compensate for) My question is, can the crank be repaired and brought up to spec? Or does anyone know of a used crank out there? And lastly, how much are new ones? I have searched the web but cannot find one listed anywhere.

 

[lens12]

A machine shop would have to check it, to see if it is rebuildable. We can't tell you without measurements. New crank is listed in the parts price list. I have a used one that would need to be checked. I'm an authorized Yanmar dealer.