Partial overhaul on Yanmar 3TNE88

[Mechanos]

On the surface these Yanmar engines looks kind of complicated, but they are really quite simple. Tear was very easy and quick. It only took a couple of hours to completely disassemble and strip it down to a bare block. All I have left to do is knock the freeze plugs out of the block, do some measuring and then it's off to the machine shop.

 

[Mechanos]

Dropped off the block and the head at the machine shop. As soon as the shop lets me know what parts the head needs, I will place an order for all the engine parts needed. Once those arrive, the shop can complete the machining and get everything back to me. Hurry up and wait....

 

[Mechanos]

Complete rebuild on Yanmar 3TNE88

Heard from the machine shop today... all the head needs is a valve job, and of course new valve stem seals. So, I placed the order for all the rebuild parts from the Yanmar distributor: pistons, rings, piston pins and bushings, inserts, gaskets, blah, blah, blabbity blah. Continue the waiting game for the parts to arrive. The machinist wants the new pistons in hand so he can bore the block and match fit the bores to the pistons.

I know the thread title started as a partial overhaul, but it didn't take long for this to turn into a complete rebuild.

 

[burnieman]

Often times the simplest things can turn into the most complicated projects Mr. Mechanoise. If you can apply the fromtasion theory to your project you will move forward with ease. Also your valves in conjunction with the race bearings and journals will work better in tandem and unison if your Simmons gear is made from steel and not cast. The link that is the strongest is well inside the crank as you probably know. If you replace it, remember that you must change the gap carefully. Most of them will be on the right side of the Sinclair induction system which may or may not be applicable to your motor. Yanmar varied through the years.

 

[Diesel breath]

Well said. If you take your time and think things through you will get the job done in a more efficient way. I don't know about too much other than farm stuff but I'm pretty good at it and I have many hours at the wheel of many different tractors. I once ate 28 hot dogs at a contest. I was full and had trouble going to the bathroom the next day. It's the same thing with tractors.

 

[Agent Blue]

Would you be better off buying a used engine ( I know, used is what you have ) with documented hours or research if a slightly larger hp model would fit ? Your speaking lots of expensive parts for a lower powered compact. Just exploring options..

 

[Mechanos]

I did look around for a used engine, but they weren't exactly growing on trees around my area. The engine I am rebuilding is already a "slightly larger hp model" than the original engine. 955's came with a 3TN84 @ 33hp. What I have is a 3TNE88 @ 37hp. Keep in mind that I am getting my parts directly from a Yanmar distributor and NOT from a JD dealer. My total parts bill came in right at $1,000 and another $500 for the machine work (including the sleeves). When I have seen a used engine for sale, it has always been quite a bit more than $1,500 and it's true history is unknown... no matter what kind of "documentation" comes with it. When it's all said and done, I will end up with a renewed engine with zero hours on it for far less than I could get a used engine of uncertain history.

 

[Mechanos]

I need to replace the piston pin bushing in the connecting rod. My Yanmar manual lists the dimensions for an SST to remove and replace the bushings and the source for the SST is "manufactured locally". So, I went over to a buddy's house and we used his lathe to turn out the SST. I used the critical dimensions for the tool as listed in the manual, but modified it's design a bit. Here's a picture of the tool:

 

[techwrtr2]

I suppose if you are rebuilding an engine you probably will know of at least one decent machine shop.

 

[Kyle_in_Tex]

Good thread. Sorry for your troubles. Sure would like to know who and what did whatever to that engine. Do you think they ran it low on coolant and overheated it and ran it hot for lengthy periods.