new/used/rebuilt engine needed for JD 4100

ericm979 · Aug 29, 2020

Pull the injectors and turn it over with nothing in it so you know what it's like. Then put in one at a time to see what each cylinder feels like. Better yet, buy a compression tester for diesels. If one tests low, put a few cc's of oil in and do it again. If compression goes up, the rings are worn. If it doesn't, the valves or head gasket is the problem.

coloradotrout · Aug 29, 2020

Would using the glow plug opening be the same? Looks like there is a 10x1.25 adapter in the harbor freight compression kit also.

ericm979 · Aug 30, 2020

Yes that works too.

dfkrug · Aug 30, 2020

coloradotrout said:
Would using the glow plug opening be the same? Looks like there is a 10x1.25 adapter in the harbor freight compression kit also.

Interesting that you have glow plugs. Many of those DI Yannies for JD tractors use a heated intake instead. Or does the replacement engine have a different head?

I have never done a Diesel compression test, as the injectors are often very hard to remove, and you can tell other ways when you have a "bad hole". Great if you can use GP hole for gauge.

coloradotrout · Aug 31, 2020

(PS.. via mobile, my posts keep getting deleted when I try to edit)

I used the glow plug holes. I'm getting no measurable compression. I can hear air coming out from the bottom of the pistons. There is some compression - I can feel it with my fingers, but not nearly enough to register on the gauge. The spec is 498 psi.

I pulled all 3 glow plugs. It does crank over easier with them out. I put one back at a time and tried to measure. Nothing.

But at 498 PSI, I cannot imagine being able to turn the crank.

There's no oil in the engine (obvious since I have the pan off!). There was some, maybe a cup or so that poured out when I took the pan off. Pan looks good. No metal particles.

Am I missing something obvious? Is oil and heat needed to make these "air tight". I cannot imagine all 3 have major compression loss.

I want to put it all back together and start it up, but that's probably 20 hours for me. A lot to lose if I have a compression loss.

coloradotrout · Aug 31, 2020

I repeated the glow plugs insert compression test with a drill spinning the crank. Until I twisted and broke off the socket adapter I was able to get about 50 psi. That was 3 or 4 rotations. Plan now is to clean up the old engine pan, pan spacer, oil tube, crank cover and bolt them loosely in place. Then tip up the engine, strap it down, put on the mounting plate, flywheel and original starter and give it a spin that way. If compression then checks out, I'll proceed with putting the newer engine in the JD. There's red RTV on the Yanmar engine oil pan, grey/black on the JD. Which RTV should I use? block to spacer block, crank cover, oil pan to spacer?

As a side note, I compared the fan/alt belts. Mine with 1800h is at least 2x more cracked than the replacement engine. No idea if that translates to the replacement engine being much newer.

coloradotrout · Sep 1, 2020

I did a leak down test. Cylinder nearest the fan was 59 of 60 psi, next two cylinders 23-27 of 60 psi. I applied 60 psi input and observed the cylinder pressure. It's all leaking from around the rings. That's a cold engine - obviously since I have never attempted to run it. It's still sitting on the bench. I did watch the pressure through the piston motion and it varied some, but at TDC that's what I observed.

coloradotrout · Sep 3, 2020

Bruce is confident it is fine. He's agreed to 7 weeks from delivery to warrant the engine of excess oil consumption or loss of power. On to assembly.

Suggestions on rtv for block spacer, oil pan, crank cover? Suggestions for anything on the other paper or metal gaskets?

dfkrug · Sep 3, 2020

coloradotrout said:
Suggestions on rtv for block spacer, oil pan, crank cover? Suggestions for anything on the other paper or metal gaskets?

Most Permatex RTV silicone gasket material is fine. You can substitute it for a paper gasket if there are no clearance issues. No sealants on the head gasket.

A leak-down test is the gold standard, and that is what I do. Sounds like you have bad rings.

coloradotrout · Sep 3, 2020

dfkrug said:
A leak-down test is the gold standard, and that is what I do. Sounds like you have bad rings.

Yeah, I'm afraid of that. Bruce insists his engine is good. Odd that 2 are nearly identical but in the 25 of 60 psi range. Hate to spend hours buttoning this all up, but he's convinced his engines are good. I hope so too!

Head is on. I *just* need to swap/add fuel transfer pump, a bolt-in plug, solenoid shutoff, oil spacer, oil pan, crank cover, mounting plate, flywheel, and the other ones I'll remember (I hope) as I run into it!

Oil spacer, oil pan, need rtv. Most others are paper/metal gaskets that I have. Should I put any gascacinch or such on those? or just dry?