Update to JD 755 challenges - 2 obstacles remain

[Moukie]

Good morning, and Happy Holidays to all!

I had posted a couple months ago about a JD 755 CUT i purchased that had many, many issues; the biggest of which were the low oil pressure (10 psi at idle), and dysfunctional 4WD. Well, i have done a lot to the tractor, including:
1) Changed all fluids, filters, etc, using correct filters and fluids.
2) Cleaned, cleaned, and cleaned some more
3) Fabricated new side covers to replace missing ones; though i have not yet painted......low priority.
4) Completely rebuilt the trashed bucket....new hardened 1/2" cutting edge and new pins, clips, paint, etc. Looks great.
5) Rebuilt tilt cylinders to stop gush of fluids. I think the lift cylinders still need rebuilt, as lift will not pick up front of tractor. No eternal leaks - possible internal..
6) Rebuilt PS cylinder to stop bad leak. This involved cutting apart and re-welding.. No big deal, and only cost $17 for seal kit. Much better than $300+ for new JD one.
7) New glow plugs and new controller. Now cranks easily in any temperature. All 3 were non-functional and module was missing. PO told me that Yanmars were notorious for being hard-to-start?? Not this one with working GP!
8) Re-worked 3 point linkages with correct pins, links, etc. Got rid of coat hangers, bolts, and whatever else was used. Looks good now, and will work as designed.
9) Fixed broken tach cable, so now has working tach and hour meter. Nice to have!
10) Fixed broken seat belt and brackets, so now has working seat belt. Important to me, as i like feeling safe. Plus, it looks good when it works right!
11) Freed rusted seat mechanism so i can now reach pedals.
12) Repaired all broken/frayed wires, connections, etc. PO said alternator did not work, and battery was no good. Both work fine for me with new wiring!

Still much more i can do. I sort of like this thing, and really want to get things working right! Two things are plaguing me, and this Holiday Season has given me the time to dig deeper. Here are my issues:

Oil pressure......Light flickers at idle, and mechanical gauge confirms 10 psi at idle. I went to my local (Spartanburg, SC) dealer and was quoted over $300 each for rod bearings. After i picked up my jaw, i decided to not pursue fixing but to sell tractor. Well, you all helped me in another post on the parts/repairs forum - thank you. I was able to buy new OEM rod bearings for about $13 each off Ebay. Bought all 3, and was fully prepared to buy mains too, after measuring wear with Plastigage. But, i went to remove oil pan yesterday and some wise PO has secured pan bolts with red loctite and lots of torque. Yep, heads are rounding off. I was able to get one off and saw the red loctite, so i baled on that project until i thought it out a bit, as i am not too crazy about using a torch under a blocked up tractor under a shed attached to my house. I decided to further investigate the second big obstacle to see how bad it is before i commit to removing engine completely.

Ah yes, #1 led me to second big obstacle.....non-working MFWD. PO fully disclosed that it did not work, but stated it was fixable and he had simply removed shaft so it did not make noise. He had very flat ground, unlike me, so not a real issue for him. Turns out, the right side (as viewed from operator's seat - the one with the PS rod attachment point) steering arm has been broken and welded. I suspect that is a contributing cause of issues, but not sure. Weld actually looks quite good. PO did remove the internal drive shaft that goes from differential to the spindle drive. Upon tearing into it, the only significant part i see missing is the 8" spindle vertical drive shaft. Left side assembly appears to all be there, but right side is a mess. I will post more later, but would certainly be interested in buying an entire assembly if anyone has any thoughts on where i can get one. I am very leery about putting this back together with that steering arm having been broken, so even that part alone is a great find if anyone has one. Looks like i can buy a substitute replacement from JD for about $362, but would prefer OEM if available. Any thoughts on this?
I am off today, so will dig deeper, but wanted to give an update, as it has been a while since i have posted. Been hard to get time to work on it, and we are in the midst of monsoon season in SC...HeHe.

I hope you all have a safe and wonderful New Year's Eve and Day. Thank you in advance for any advice you can offer about the above issue.

David in rainy SC

 

[jthibodeau89]

If you have access to a TIG welder, you can apply low amp heat to the center of the bolt head. Do not make a puddle, just a spot. Intebtion is to apply heat to bolt for a few seconds. Let cool down, and attempt to remove. All bolts heated this way will need to be replaced. I replaced most of the mix of main bolts on my JD4300 with grade 10.8 flange head bolts.

 

[pmsmechanic]

Subscribed

 

[Moukie]

Happy New Year to everyone!

I had a fun day yesterday tearing down the MFWD unit. Found out that things may not be as bad as they could. The left side appears intact; though well worn. I will use it as a guide, along with the manual, to rebuild the damaged right side. I bought seals, sleeves, bearings, etc for both sides, so all will be freshened up. My local dealer processed my order and expects to have everything i need Thursday, so maybe i can get this all back together before i forget how it came apart.....HeHe.
The jury is still out on the welded steering arm. I will be watching close as i begin reassembly to see how well parts do or do not align.

I only have a plumbing torch to heat the oil pan bolts, and the flame is wide and not adjustable. I may try to place a socket over the bolts first to keep the heat on the bolt only to see if that will free up the thread locker. Just a few seconds will hopefully do it. I will post back after i give it a try.

Hope you all have a wonderful start to the new year. Any and all suggestions are welcomed and appreciated.

David in SC

 

[Zebrafive]

I think heat is the only solution to loctited bolts.

I am wondering if you could heat a piece of metal red hot and then touch it to the bolt, with hopes the heat will transfer to the bolt?

 

[beenthere]

Good excuse to get the torch with the pencil flame tip..

 

[jthibodeau89]

Yes, heat concentrated on the bolt is the best way to get loctite to release its grip.

 

[Moukie]

Today's update: I am anxiously awaiting my shipment of MFWD parts from JD; supposed to be at the dealer tomorrow. Yipee! I now have everything cleaned up, and ready to begin re-assembly to see if things look like they will fit properly. I am a bit scared about the welded steering arm (upper spindle housing), as imperfect alignment here could yield a waste of time and money for me, but we'll see.

I also went back at the oil pan bolts for a while. I first tried my heat gun with a 1/2" drive socket over the end to funnel the heat to the bolt. No luck. I then tried a charcoal grill lighter (long bic); no luck. Lastly, I got out the plumbing torch; again no luck. I could never get the head of the bolt over about 240F. I am sure I could have gotten hotter with the torch on for a longer period, but I start getting a bit nervous with erratic flames around hydraulic lines and such. Bottom line; with an engine block at 50F, I cannot get enough heat from the external sources I have to get the bolt anywhere near the 500F it needs to be to free the red threadlocker. I love the idea of the tig torch, but I don;t have one and this hardly justifies buying one. Plan now is to put fuel tank back on (spent a while today emptying it, fixing siphon tube, and cleaning it out), replace ancient fuel lines, and crank her up to run a while and generate some internal heat. Maybe that will help me generate enough heat to allow me to get bolt hot enough. If this does not work, I have no other plans. Any thoughts?

I will really hate if I succeed in getting the MFWD working, but cannot get the pan bolts out to check/change rod and main bearings. Honestly, I am fearful of what I might find when/if I get the pan off. Reed threadlocker on a pan bolt is not a good practice, with what I know. Might find that or worse inside the pan!

Any and all thoughts are appreciated. Thank you much.

David in SC

 

[jthibodeau89]

TIG torch is really the best way for your situation. Any nearby friends have a TIG machine? Perhaps a tool rental place near you? Or maybe uou could try a small tip on an oxy/acetylene torch. Be sure to use a 6pt socket when removing the bolts.

 

[Moukie]

Well, another failed attempt. I put fuel tank back on and filled oil pan so i could run. That brought engine temp to about 150F. I bought a pencil tip nozzle for my propane torch, but that still was not enough to break loose the pan bolts. Looks like i may still have to remove engine to put on a stand where i can really heat up the bolts and focus my efforts better.. Before i do that i have to get the MFWD back together and off my workbench......just not enough space for it all in my workshop. Having the MFWD off really will make it easier to pull engine off though. I really don't want to go that far, but?

Parts at dealer were a day late, so should be in this AM. I will be beating at the door first thing, as time now to go back to my paying job.

Have a nice day to all!
David in SC

 

[Moukie]

Hello to all......brief update to where i am. I got the front end all put together; basically with all new bearings seals, shafts, etc. I put it back on tractor and ran it on jack stands Sunday and everything appears to work as it should. No odd noises, or obvious tricks. Had a really hard time getting dope in the spindle fill ports; can easily understand why they could be overlooked or neglected. I think she is ready to run from the front end standpoint. Yes!

Now that gave me a compelling reason to get back on the engine to investigate the oil pressure issue. After several hours of work, i got pan bolts out and tonight i got pan off. Initial take is OK. I took off 3rd main cap away from oil pump; one slight groove, barely enough to feel with fingernail. Journal looked super. Measured with plastigage and came up with about .003". I don't have manual in front of me, but i believe initial spec is .0015, and replacement is suggested at .006"? Seems like i would not be having 10 psi at idle with only that much wear, but i am not an expert. Does that seem correct? Engine block and ambient temp is about 40F.
Next, on to the middle rod bearing. Same story, about .003" with plastigage. I believe same specs as main bearing clearances.

I was really hoping to find something very obvious, but i did not. Now the decision is whether i go ahead and install new rod bearings which i have. Should i order and put in new main bearings? Or, should i maybe pull engine and look elsewhere like oil pump?

Any advice you all can give is great. I am kind of in a conundrum at this point. Just checked manual and it states .001-.003 is ok; replace at .006. Now what? Pull more caps? Oil pump? How hard is it to remove oil pump, and does injection pump have to come off first? If yes, is that tough to re-install? Never done that before.

Thank you,
David in SC

 

[beenthere]

What does your service tech manual say for pulling the oil pump?

 

[Agvg]

Suppose you have checked the pressure valve for the oil pump? Are you lucky it's just a bad spring or adjustment. No cracks in the oil pickup?

 

[Moukie]

Oil pump is next to read about. I suspected bearings because the psi drops way low on hot engine, but psi is not good on cold engine either. I will look close at OP. Pickup tube is on and screen was not clogged.

Thank you for the feedback.

 

[Agvg]

Have you tried to measure clearance with a new bearing?

 

[Moukie]

I have not....got too late and too cold. I may do that tonight; let me read up today on oil pump removal and check procedures. Do you know if i can remove OP without removing engine?

 

[mike48130]

Like AGVG said check the oil pressure relief. Usually a spring with a steel ball or plunger. They can wear or get dirt in them and not seal properly. Also when you get it running, pull the valve cover. Sometimes there are oil galley plugs. Possibly one is leaking or fell out. I think if your oil pick up line had a leak, you would get foamy oil from the air.

 

[Moukie]

Thank you for all the feedback. Plan for tonight is to pull the main bearing farthest away from the oil pump; if it looks good like the one next to it, I will torque those two mains up and check one more rod bearing. I might go ahead and install the new rod bearings since I have them. I will plastigage them to verify clearances before I final torque them. I also intend to remove the pump pickup tube and verify 0-ring condition; screen and bottom of tube look to be ok. After all this, I think I need to pull oil filter and the spring/plunger assembly to check it out. If all that checks out OK, not sure what the next step would be.

Thank you so much for the advice. I am getting very excited about being able to use this machine. Should be in pretty good shape once I finish up all I am doing.

David in SC

 

[Moukie]

Good evening from rainy SC. Finally figured out the low oil psi issue. The other night, I pulled another rod and another main bearing. Plastigage shows .003", which is inside spec, and everything I could see looked to be in great shape. So, I pulled the oil filter pressure valve. Ah ha. Spec for the spring is 43.5 - 48.5 relaxed, and mine was 37mm. Had two 0.5mm shims, but still nowhere near long enough to get the proper psi. Manual stated I could add 1.6 psi for every one mm of shim added, but I could have only added about 2mm before I ran out of housing room. Even adding 3.2 psi would have only brought me to about 15 psi; not near where I wanted to be. So, two days and $82 later, I picked up my new pressure valve assembly today; JD would not only sell me a new spring. No problem; really a small price to pay for what I got. I torqued everything back up, cleaned up and painted oil pan, and started her up just before dark.. Wow, 56 psi! Unbelievable difference. Oh yeah, I went ahead and adjusted valves while I was in the area. Took longer to access valve cover than it did to remove oil pan.
I am tickled now. Have a working 4WD tractor with a super-strong engine. Now, I can get to using it and not have to worry about the oil pressure. So happy.

Thank you all so much for your help on this. I am sure there will be more, but for now I will likely use the tractor and quit pampering it.

I actually had this happen once before on a freshly built 8N. Maybe next time I will remember to check that before going much deeper.

Thank you all, and have a nice evening,
David in SC

 

[beenthere]

:thumbsup: :thumbsup:

Thanks for reporting back on the successful find/fix. Good info for the TBN archives and good for you to have the up-and-running tractor.