new/used/rebuilt engine needed for JD 4100

[JustGary]

You can test the valves by pouring alcohol into the intake and exhaust ports. A good valve will hold the liquid. A leaky valve will let the alcohol through to the combustion chamber side of the valve. A tiny bit of wetting around the valve is probably not bad (it's OK on a gasoline engine, but I don't know about a diesel with the higher ratio). A valve tool is pretty cheap, or maybe that hotrod neighbor has one and can help you. You can lap the valves yourself with not much effort if you find a tiny leak.

That involves using a bit of abrasive (lapping compound) to work the valve around in its seat in order to clean up the contact between the valve face and the seat.

You could also check with your local vo-tech school for tips, help, or maybe the whole class.

- Just Gary

 

[tlbuser]

</font><font color="blue" class="small">( He mentioned "mic-ing" the cylinders? What is that? And also checking for tapered cylinders - that there may be more wear at the top than bottom. How do I do that? How do I know the head/valves are OK or not OK? )</font>

Mic-ing the cylinders is simply (IMO) using a telescoping guage at the top, center and bottom of the bore. That gives you an accurate internal diameter, then you would use a micrometer to "measure the measuring tool (guage)". Then you can make an accurate judgement on cylinder wear and taper. Hopefully, that machine shop was quoting you a worst case rebuild number. That was (IMO) way too much money for what you said was done. I haven't lived in the area for quite awhile, but I'm sure there's another shop around.

 

[coloradotrout]

I have the caliper. so I'm halfway there.. haha.

OK.. so what kinda of accuracy are we talking about? .0001, .001, .005, .01

I'd be OK with .005 ish. When it get's to .001, man that is tough. I do woodworking, so I setup tools, etc. and try to get to .001 accuracy. But no way, .005 is reasonable, and plenty good for woodworking.

 

[coloradotrout]

Re: cause.. rings, or other -- it's buning oil; much more visible now in the winter time. The dealer felt blowby was excessive. I had nothing to base it on, but he felt for this small engine, it was bad. The dealer did not want to do a compression test. I still don't like that, but I did not want to pour $200 more into it. Harbor freight sells a couple of diesel compression testers. The issue is the specific fitting for that JD 4100 tractor. http://order.harborfreight.com/EasyAsk/harborfreight/results.jsp

 

[Mike_Lipke]

Dealer is prolly right. Blowby is excessive means rings are not sealing, either due to bad rings or scored cylinder(s). A $200 compression test will only tell you what you already know.
Worst case:
You pull the head, take a look see and find the walls are scored. Put a new head gasket on and bolt it back up. You are out 2 hours and the cost of a gasket. You can then sit back, use the thing, and consider your options over a cup of tasty beverage. You at least will know what you are dealing with.

Best case:
Rings have lost their temper, causing blowby and oil consumption. Rering, have head checked, maybe valve stem seals as long as you are that far into it, bearings, bolt it back up.

Every engine manual gives alowable gaps for the rings. You can use a feeler gauge. Range is from about 10 to 20 thousanths (.010-.20).
This varies by engine, but there is a table, and your dealer will surely share that with you. There is also a number for maximum taper, which is checked with feelers and the ring at the top and bottom. This number is also on that chart. Get a copy of the page if you can. The machine shop may need some of that info to check ring groove clearance. Can't hurt.

If my doctor says I need my appendix removed, he is probably right. There is always the chance that when he/she "gets in there" that there will be some other terrible thing wrong, but probably not. There is a saying in medicine, that if you hear hoof beats, think horses, not zebras.
You may have something else wrong inside that engine, but I hear rings.

 

[tlbuser]

For checking the bore, .005 tolerance is plenty. The bore is what, 74mm? After removing the head, you could turn over by hand to check at least two reference points on the bore. The cylinder wall condition will also give you a clue of what you're looking at. If it's got heavy, black vertical streaks, odds are it'll need to be professionally honed and polished.
These guys diesel shop might be willing to tell you where to get some good help.
There's also a whole engine here engine

But, I would strip this one down and check it out before making any decisions. Have you called any of the Yanmar places to see how much a "rebuild kit" is and what's in the kit ?

 

[coloradotrout]

bore std 74.00-74.03mm, wear limit 74.20
piston to cyl clearance .030 - .060mm (.002 in)

I'll get a scanner and post pages of the manual as I get started.

 

[coloradotrout]

Okee.. I'm reviving this thread. I'm back, and it's about time to now get serious. Previous owner has agreed to pay for parts as I work on the engine. He also gave me a fair labor allowance. I'm ready to pull off enough parts to peek down into the cylinders. I bought a set of telescoping guages and I have calipers, wrenches, torque wrenches, etc. I do not have a ring compressor.

What words of wisdom do you have as I begin? Drain coolant.. pull off topiside and take a peek? Drain oil and pull off bottom side and see about pushing out the cylinders?

I have the Technical Service Manual. I have to remove various top side parts to get to the head. Might "frozen" bolts be an issue? Should I douse them with wd40 or other and let them soak before trying to remove? I'm concerned about "twisting off" a bolt. That seems like a complete disaster should it happen.

I read back through all the old posts. Thanks for all the info. I'm a little anxious, but it should be interesting.

 

[bones1]

Ok Good luck, you can do it. Use PB Blaster on any bolts that you think are frozen, just let em sit and they'll come loose.Get a couple coffee cans of new motor oil ready for re-installing the piston&ring assemblies as well.

 

[WayC]

Reading your post brings one thing to mine that you need to be sure of if you do your own repair. I work at a small machine shop in Roswell and we do a lot of small yanmar engines. We did a small 3 cylinder like you have only it was used as a pump engine. It had be over heated and we were able to jusr hone the cylinders, install new rings, a valve job... including millng the head, it was warped. One of the things that you really need to have checked are the injectors, all of these had been cooked when the engine over heated. You should be able to have yours checked at any good injector shop and have them repaired if needed.

This little engine is used to drive a pump to fill a stock tank by a local rancher. He is usually very good at the up keep but this one got by him..

If you will get you a good repair book, repairing this engine should not be too bad.

This is my penny and a half's worth..

Wayne