b7100 only 800 hours and rebuilt - why?

comfun1

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b7100 with 1630c loader
Jul 28, 2015
46
0
0
Independence
Around 1992 I bought a brand new b7100 with a 1630C fel and a 4' bush hog and 5' box blade complete with tandem axle trailer for the grand sum of $10,500. At 875 hours the cylinders had to be bored and the pistons and rings had to be replaced with the next size over. I now have about 1400 hours on it and so far no problems. I have always wondered what could have caused this and don't want it to happen again. I always changed oil and filter and kept the air cleaner clean or replaced.

Here is a little history of it's use.

For several years I used it to till several acres of ground that I grew pumpkins on. The tiller probably was used once or twice a week throughout the growing season. Depending on the condition of the ground the tiller put a real strain on the engine. At one point I had a high school boy helping me and I observed him tilling. His technique was to set the throttle wide open drop the tiller all the way and ram the hydrostat pedal to the metal. Then just before the engine died he would let off and when the rpm peaked again he would repeat the process.

I also used it to clear a lot of woodland and I would cut trees with a chainsaw and use the tractor to push them into a burn pile. As the fire burned I would drive the tractor as far as I could into the burning pile and compact the limbs with the loader. Also while the piles burned I would continue to push and carry more limb onto the pile.

Other than the above the tractor has just been used for post holes, moving dirt and gravel, box blading, raking etc.

I have a couple of ideas that might have made it wear out and would like to know what the rest of you think.

In the case of the tiller, could the extreme load have caused the engine wear? Could it have been the technique of my teen age helper?

In the case of the clearing and burning I have always wondered about the effect of ashes. Could the ashes have been so fine they were able to get through the air cleaner?

Then I wonder about the fact that I used high sulfer off road diesel? Or at one point my pipe broke off my muffler and I wonder if rain could have found it's way into the cylinders?

Any ideas that could prevent me from rebuilding again would be appreciated.
 

Lil Foot

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1979 B7100DT Gear, Nissan Hanix N150-2 Excavator
May 19, 2011
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What you describe sounds like pretty severe use for any tractor, let alone one as small as a B7100.
My 1979 B7100DT has over 1400 hrs, and still runs like a top.
 
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85Hokie

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BX-25D ,PTB. Under Armor, '90&'92-B7100HST's, '06 BX1850 FEL
Jul 13, 2013
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Bedford - VA
I have the exact same year - 92 and almost the same hours - 785 , bought the ol girl used but not abused. I hope mine does not need a new engine anytime soon!

the sulfur should have "helped" - sulfur acts as a lubricate in the process (along with polluting the air), now as for the fine particles - that might have been a bad thing. I have no idea what would cause the early failure of your engine. The water damage could be a problem too. Others will tell more of the likelihood of why it failed so soon.
 
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hodge

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John Deere 790 John Deere 310 backhoe Bobcat 743
Nov 19, 2010
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Love, VA
Without doing an oil analysis, it is hard to tell what happened.
1) It could have been a lemon engine, destined to only hold together for 800 hours. It does happen.
2) It can happen due to poor maintenance. Without knowing what oil you were running, how often you serviced it, how you maintained the cooling system, etc., it would be hard to say. Obviously, running the incorrect oil, waiting too long before changing it, engine overheating, etc. can all lead to early failure.
3) I would be suspect of the ash- if that got into the engine, it would do damage, no question.
4) You should have stopped your young helper when you first witnessed him operating the tractor the way he was. He didn't do you any favors. If you didn't correct his habits, and you worked the tractor on a regular basis as described, it is severe duty, and will shorten the life of the tractor. There are many owners with 5 times those hours, and still going. I have almost 900 hours on my 1990, and it is in new condition- uses no oil, high compression, starts well in cold weather, etc. The engine is still tight and strong.

If you still work the tractor as you have in the past, I would consider getting a bigger piece of equipment. It isn't the tractor's fault if it is being worked beyond what it was designed to do.
 

Bulldog

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M 9000 DTC, L 3000 DT
Mar 30, 2010
5,440
73
48
Rocky Face, Georgia
Some of that does sound like severe use but I can remember putting my 7100 thru some hart times. At times I worked the crap out of mine and when I traded it off it had over 6000 hrs on it and still running strong.

What kind of oil do you use and how often do you change it?
 

ShaunRH

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L3200
May 14, 2014
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Yeah, the kid was literally doing the worst thing to the engine you could. The HST pedal is not a throttle pedal. He was forcing it way above the 'gearing' it should have had for running a tiller.

I'm surprised that motor didn't overheat and seize, or it came darned close a lot of times and that would explain your wear. The rings and sleeves were literally going soft against each other and at that level of heat, the oil is mostly useless. Then all the metal in the oil would force the plugged filter bypass very quickly, way before the common hour mark, and you were running abrasive oil for half a change cycle and you didn't even know it.

That's my WAG analysis from the description... probably worth about half the words that I actually used, so call it bonus text. :D
 

sitdwnandhngon

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B7100
Aug 25, 2015
45
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NY, USA
Continuously bogging a diesel is not terribly good for it.

Mix that in with some overheating and it is probably a recipe for disaster.
 

lugbolt

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ZG127S-54
Oct 15, 2015
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Mid, South, USA
Look closely at a B7100. It is a light duty homeowner tractor made to mow grass and that's about it.

Lot of them didn't even have a water pump. The ones that did, even those had a poor cooling system. Overheating was fairly common. Radiator had to be kept squeaky clean, coolant should be 50/50 distilled (not tap) water and ethylene glycol (green) antifreeze mix.

Then the air filter. It pulled fresh air from outside the engine compartment. Right where dirt is. Great design. When an air filter on a diesel gets dirty, air is restricted to the engine. On a gasoline engine, air and fuel are introduced through the intake valves. When the air fuel mix gets into the cylinder, it helps cool piston tops, valves, etc. On a diesel, you don't have a fine mist of fuel going into the engine during the inlet stroke. Just air. Air does the cooling. When the air is restricted, the tops of the pistons get hotter than normal, worse when under constant load. Or course it's the job of the piston rings to dissipate some of that heat into the cylinder walls. The rings get hot too. When they get too hot, the ends can try to butt together, which (1) wears the bores faster than normal and (2) sometimes results in seizure.

So combine a heavy loading of the engine, possible filter restriction, and a poor cooling system from the get-go, and you have my opinion of what most likely happened.

When I say filter restriction, when it's dirty, replace it...not blow it out or tap the big stuff out, replace it. Tapping the big stuff off leaves the paper still dirty...you can't see it but it's still there. B7100's needed all the help that they could get in a lot of departments. They did pretty good mowing grass but that was about it.
 

Hondarancher4435

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B8200
Oct 8, 2014
17
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Pa
Something to think about. I also had a b7100 that needed the engine rebuilt around the same hours. Cause was low oil pressure due to pressed in plug falling out of cam shaft and then the engine builds minimal oil pressure. Once I put a new plug in oil pressure shot right back up but it had been like that long before I bought it so the damage was already done, it huffed blue smoke the entire time it was running. I highly suggest you check your oil pressure with a manual gauge
 

comfun1

New member

Equipment
b7100 with 1630c loader
Jul 28, 2015
46
0
0
Independence
By the way, I did stop my helper when I noticed what he was doing but I have no idea how long or how many days he had been doing this before I noticed.
 

85Hokie

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BX-25D ,PTB. Under Armor, '90&'92-B7100HST's, '06 BX1850 FEL
Jul 13, 2013
10,422
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Bedford - VA
Look closely at a B7100. It is a light duty homeowner tractor made to mow grass and that's about it.

Lot of them didn't even have a water pump. The ones that did, even those had a poor cooling system. Overheating was fairly common. Radiator had to be kept squeaky clean, coolant should be 50/50 distilled (not tap) water and ethylene glycol (green) antifreeze mix.
Not getting picky - it is a SCUT - is a sub compact tractor, but at the same time it is one hellva tractor for the size that it is!:)

on another note - the 50-50 mix is really a bad idea - now if the climate calls for it, and that needs to be damn cold - then use 50-50, however at the 70-30 mark, it will cool better! Ethylene glycol is not as good as water at transporting heat, thus water is better but not ideal without the other goodies in the system for anti rust and what not.

But you hit the nail on the head with the squeaky clean part - check the radiator and then check it again!:)
 

Steve NC

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Equipment
B7100D, L2900DT, ZD21, G6200,
Dec 29, 2014
89
4
8
Sandy Bottom North Carolina
I added a brass tee to my oil pressure sending unit so I could add a mechanical gauge and still keep the original light for my B7100. I also added a temp gauge in the radiator so I could get some sort of idea of the engine's temp. My tractor also quit about the 800 hour mark due to the camshaft plug. When my relatives finally gave up on the tractor I picked it on the cheap and began restoring it. The head was cracked in two places and the valves were sharp enough you could shave with them. ( caused by low oil pressure and high heat) The original B series tractors are built like tanks and can take a lot of abuse despite their crude design of certain systems like the cooling systems.
 

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comfun1

New member

Equipment
b7100 with 1630c loader
Jul 28, 2015
46
0
0
Independence
I tapped mine right in where the oil pressure light sensor is. Left side of the engine near the rear.
I am going to install a gauge. What kind of pressure should I be seeing. I'm sure it fluctuates depending on rpm. Since my b7100 has no tach maybe some one can give me a pressure at idle and another at wot. Thanks
 

sitdwnandhngon

New member

Equipment
B7100
Aug 25, 2015
45
0
0
NY, USA
I am going to install a gauge. What kind of pressure should I be seeing. I'm sure it fluctuates depending on rpm. Since my b7100 has no tach maybe some one can give me a pressure at idle and another at wot. Thanks
Mine was about 6 cold before I did the cam plug fix, warm it was barely registering.

Now at start up idle it's around 40, after warm up idle is 30-35