JD 950 engine rebuild

[83regalsx]

Hi everyone.
I recently purchased a ‘86 950 with a 3t90j. I’m a mechanic by trade and I got it for a song knowing it had some problems and a lot of hours (3200 hours). The head is cracked and while it’s off I’m taking the opportunity to put pistons and liners in it. I have a rebuild kit from weavers coming and I have a few questions.

What have others used on their liners seals? I see a few others here have done 3t90 overhauls. the factory liners definitely had some type of sealer around the top o-ring but everything I have read just says to lube them.

Thanks in advance for any input. I will post a few pictures where I’m at so far.

 

[83regalsx]

 

[83regalsx]

 

[TimberHole]

The overhaul manual calls for a JD lubricant on the o rings. It’s some slimy stuff. I can’t get to my bottle currently as I have everything covered for a project I’m painting. You going to repair the cracks or replace the head?

Also, the JD rings were far superior to any aftermarket options I found. The markings on the rings were an exact match for those removed. I didn’t think much of the aftermarket head gaskets either so went with Deere. Much better looking gasket although a bit more pricey.

Edit: There is no sealer on the o-rings, just a lubricant.

 

[rScotty]

SNIP

Thanks in advance for any input. I will post a few pictures where I’m at so far.

Re the liners. Yanmar used to recommend that the liners be put in with lube and no sealer. I'll have to go do some digging to if I have any notes on installing liners.

Looking at the pictures the liner that you pulled out has a lot of erosion. What do you think caused that?
rScotty

 

[83regalsx]

The overhaul manual calls for a JD lubricant on the o rings. It’s some slimy stuff. I can’t get to my bottle currently as I have everything covered for a project I’m painting. You going to repair the cracks or replace the head?

Also, the JD rings were far superior to any aftermarket options I found. The markings on the rings were an exact match for those removed. I didn’t think much of the aftermarket head gaskets either so went with Deere. Much better looking gasket although a bit more pricey.

Edit: There is no sealer on the o-rings, just a lubricant.

I will be ordering a new loaded head from Hoye tractor. I also went with a headgasket from JD, price wasnt that bad at $60 either. You think its worth the extra money for a set of JD piston rings as well? I just got my kit from Weaver and everything looks pretty good except I don't like the snap rings for the wrist pins as much as the OE clips and the oil ring didn't impress me that much. I was going to live with it though as it is just an in-frame on a high hour machine. If you wouldnt mind posting the part number on the bottle that would be great.

 

[83regalsx]

Re the liners. Yanmar used to recommend that the liners be put in with lube and no sealer. I'll have to go do some digging to if I have any notes on installing liners.

Looking at the pictures the liner that you pulled out has a lot of erosion. What do you think caused that?
rScotty

And thats how i was under the impression it should be done as well, i was thrown for a loop upon disassembly when i found the "goop" all over the top ring. Who knows, maybe it was due to the o-ring breaking down and getting mushy.

The liners are in very rough shape. I am guessing that perhaps this tractor ran with a cracked head for a long time and had corrosive combustion gasses in the coolant for quite some time. Assuming low quality coolant and lack of maintenance was an issue as well. When I purchased the machine it had been sitting for six months, previous owner knew it had an electrical problem and couldnt get it running but he was unaware of the engine problems when i told him.

 

[83regalsx]

Here’s where I stand now. I ordered The head from Hoye this morning along with a few other hoses and little bits. Going to get some John Deere lube possibly today. I have everything cleaned up and washed down. The o-ring grooves in the block look great. Going to swap the pistons into the old rods next and I should be good to go and just be waiting on the head to show up.

You can see some corrosion in the last picture but the backing side of the o-ring groove looks great so I’m not worried.

 

[jaydee325]

The corrosion/pitting pictured on the sleeve and block near the o-ring groove is caused by cavitation of the coolant. This is generally avoided by recommended coolant flush/change intervals.

Just google diesel engine coolant cavitation to learn more.

 

[rScotty]

The corrosion/pitting pictured on the sleeve and block near the o-ring groove is caused by cavitation of the coolant. This is generally avoided by recommended coolant flush/change intervals.

Just google diesel engine coolant cavitation to learn more.

That's where I was going with the original question. Cavitation rather than Corrosion. Or maybe both together.
Cavitation pitting has always been a problem with liners. They can ring like a bell.
Wonder if liners are available at a reasonable price?

 

[TimberHole]

My old liners had corrosion above the top o-ring also. I think it’s because people don’t take care of their coolant. I think the JD rings are worth the extra money but that’s just my opinion and you know how those are. I would also consider some locktite when installing the studs in the block. These engines are pretty good at blowing head gaskets and I have come to believe the studs are not staying tight in the block.

 

[83regalsx]

My old liners had corrosion above the top o-ring also. I think it’s because people don’t take care of their coolant. I think the JD rings are worth the extra money but that’s just my opinion and you know how those are. I would also consider some locktite when installing the studs in the block. These engines are pretty good at blowing head gaskets and I have come to believe the studs are not staying tight in the block.

Like I said before, I don’t really like the oil ring that came in the weaver kit but I’m sure it’s fine. Not worth the extra $150 to me.

As for the head studs, I’ll keep it in mind. Thank you. I normally like to re-torque after a few heat cycles. Especially on an engine like this that’s so easy to do so.

how many hours were on your engine when you went through it.


I picked up some John Deere lube today. For anyone who has looked into the controversy around liner seal lube you may find it interesting that this stuff is a coconut based oil.

 

[rScotty]

Well, I can't find the info I had on sleeved engines needing coolant with the anti-cavitation additive.
But having a coolant that doesn't form cavitation bubbles does make sense.

Ditto with the loctite on head studs. I have never done that, but we all know that really picky engine builders will often replace all the old head studs with new when they rebuild. I don't go there either.... so using the appropriate loctite seems a decent middle ground.

What is the deal with the JD oil control ring being different? I would have thought that the OEM Yanmar oil control ring would be the best quality - or are we not talking OEM? Yanmar is a huge company in diesel engines.

What do you think on facing the block or head?
rScotty

 

[83regalsx]

Well, I can't find the info I had on sleeved engines needing coolant with the anti-cavitation additive.
But having a coolant that doesn't form cavitation bubbles does make sense.

Ditto with the loctite on head studs. I have never done that, but we all know that really picky engine builders will often replace all the old head studs with new when they rebuild. I don't go there either.... so using the appropriate loctite seems a decent middle ground.

What is the deal with the JD oil control ring being different? I would have thought that the OEM Yanmar oil control ring would be the best quality - or are we not talking OEM? Yanmar is a huge company in diesel engines.

What do you think on facing the block or head?
rScotty

I purchased an aftermarket rebuild kit My pistons and rings are not John Deere or Yanmar. I won’t get the block decked and my head is brand new so no need there.

 

[TimberHole]

I did an in frame with a blown head gasket at 1200 hours. Excellent machine and no cracks in head.

Split another 950 for full overhaul at about 2800 hours. Had a rod knocking. Crank barely turned and head had 3 cracks. Shop pinned the cracks.

As for the rings, the Deere rings I bought were the exact same as the rings I removed right down to the markings. Upon close inspection the aftermarket rings were yielding when installed and would not return to there original shape, even using a good ring expander.

 

[83regalsx]

Got the liners dropped in tonight and started cleaning up and swapping pistons. I found two spun wrist pin bushing and one was broken in half. The other is severely worn but not spun. These things saw some heat and poor lubrication, surprising with how good the rod bearings look. Anyway, I ordered new wrist pin bushings and will wait for them to come in to see if the rods need to go to the machine shop.

I also started checking rod bearing clearances and they were all great. On the low end of the factory spec actually. This may not matter though if I send them out.

 

[TimberHole]

I had to send my rods to the machine shop. I have a lot of tools but did not have the tools/equipment needed to ream those bushings.

 

[83regalsx]

My new head and Bushings came in as well as new rod bearings. Got the rods to the machine shop on Thursday to get the Bushings pressed and honed to fit the pins, should be done early next week. In the meantime I’m swapping parts over to the new head and cleaning things up. Shouldn’t take long once I get parts back from the shop.

 

[yanmars]

The mention of coolant. Will you use the green stuff as perhaps originally used back in its time or extended use coolant? I have a similar tractor, the Yanmar 336d and wondered about the same.

 

[bmaverick]

The mention of coolant. Will you use the green stuff as perhaps originally used back in its time or extended use coolant? I have a similar tractor, the Yanmar 336d and wondered about the same.

Use the old standby green coolant OR the Prestone OAT formula for ALL vehicles, old and new. Prestone keeps the corrosion inhibitor additives at the old levels for the best protetion.

The Extended Life coolants are engineered with minimal corrosion inhibitor additives. Thus, in our older tractors, using the Extended Life coolants would bring on the internal corrosion and a cooling system pumping brown sludge around.