Engine rebuild or troubleshooting advice

   / Engine rebuild or troubleshooting advice #1  

BigNotEasyGuy

New member
Joined
Feb 20, 2017
Messages
23
Location
Bennett, CO
Tractor
John Deere 755
I have a JD 755 that I bought off of craigslist a year ago. I have the manuals and started trying to learn how to do maintenance as this is my first tractor. I changed the coolant and the old drain valve broke, or was already broke, it had a frozen plug inside that I cleared out. After the coolant flush the valve leaked which I didn't see until later. I didn't check the coolant level one day when I was trying to till my garden and it led to a stalling problem that I posted here: http://www.tractorbynet.com/forums/j...lling-all.html

Well after that post I went out and checked the coolant and the oil level and they were both very low, almost gone. That left me with the impression that I had overheated and possibly damaged the engine. I figured out the valve was broken and got a new one ($3), then the fluid never leaked out again. During colder months I can run it ok (I also added a block heater). But this summer during hot days I can only run it for 10 minutes or less and the temp gets up near 190 which is the overheat point I've learned. The previous owner had installed a temp guage (which I wasn't paying attention too during the tilling day).

I suspect I may have warped the head maybe? I don't see anything milky in the oil. But maybe the head gasket is leaking and causing the overheating? Or maybe even something far worse. I'm no expert and I don't have a lot of time. My work schedule is demanding and we have a small 36 acre farm. I do what I can on weekends. I only mention that to say that if I can spend a few dollars to buy time I will make that choice otherwise I'm pretty frugal and like to do things myself.

What would you do? I think I have 3 options:

1) replace the motor
cost = highest
time = medium?
difficulty = ? (the tech manual makes it sound easy actually, but I've been fooled before...)

2) rebuild the current motor
cost = medium?
time = high?
difficulty = high?

3) continue debugging everything (like mystery air pockets, thermostat, etc.)
cost = small to medium
time = unknown, maybe high unless you're lucky
difficulty = relatively easy

Do you think my assumptions on cost/time/difficulty are correct? After reading posts about mystery overheating I was wondering if I shouldn't just go with the new engine although maybe that's way too expensive? Has anyone ever bought a new or rebuilt engine? If so where would I go (besides a dealer) to get something like that?

I'll make sure the thermostat is working at a minimum but when the engine gets hot and close to overheating it will spit out a ton of black smoke and it will start lugging like it's going to stall. I just shut it off and wait for an hour and go back and do another 10 minutes of work. In the evenings I can make it last longer, also if I just sit with the hood cracked and turn the throttle all the way down I can watch it slowly cool itself down. I assume that means the pump is working and that the thermostat is opening assuming that cooling itself while running and not moving means it's cycling coolant.

One last update, yesterday while trying to lift a 750lb hay bale I appear to have pushed the radiator into the fan and now the radiator is leaking coolant. So, I'm probably replacing the radiator soon if that alters the answers to the above questions...

Thanks for any thoughts and advice. :)
 
   / Engine rebuild or troubleshooting advice #2  
Your link didn't work but I found the thread

http://www.tractorbynet.com/forums/showthread.php?t=376506

I'd continue troubleshooting before tearing apart the engine. Check compression at a minimum. If you don't have a way to do that try cracking the injector lines one at a time when it's running to see if each cylinder is contributing equally. If you crack a line and you don't notice a change in the sound/rpm/smoothness of the engine then you could have bad compression, injector or something wrong with your injection pump. Wear gloves and eye protection when dealing with the high pressure fuel lines.

As far as a new engine you're probably looking at several thousand dollars. If it comes down to it rebuilding would be the way to go IMO. I'd just hate to see you dump thousands into a new engine only to find out you have a bad injector or pump.
 
   / Engine rebuild or troubleshooting advice #3  
Make sure cooling system is working before rebuilding or replaceing engine. You should also make sure that the problem isn't only blown head gasket before wading in to new engines. Had you not mentioned black smoke and lugging,I would have said 190 sound's like operating tempature. If you can't be vigilant with maintenance,buy gasoline next time because diesel is very unforgiving. Last but something to consider,diesels require more skill to work on compared to gasoline.
 
   / Engine rebuild or troubleshooting advice #4  
Do a new thermostat.

Changing the antifreeze was easy with no air pocket drama on my JD 870.

190F is not hot. No actual numbers on my temp guage. My JD 870 doesn't run very hot brush cutting or heavy mowing. I have no idea about that engine but some cars have water pumps with plastic impellers. They slip. I prefered water pump in those cars with metal impellers.
 
   / Engine rebuild or troubleshooting advice #5  
When the head gasket went on my 4300 I drained the coolant, took the water pump belt off, stuck my ear to the radiator cap hole with the cap off, and idled the engine for a few seconds. I could plainly hear the leak, sounded like an exhaust tick in the radiator.

I doubt you need a rebuild, just a head gasket should do it. Easy to do on that tractor, if you have the gasket in hand and a good straight edge and some nice big flat fine files you should be able to do it in a day.
 
   / Engine rebuild or troubleshooting advice #6  
I too, would go the trouble shooting route.
A pressure test of the cooling system (even if you pay a dealer to do it) should be first step BEFORE replacing the head gasket.
190° does not sound too hot.
Thermostat, radiator cap replacement would be good second steps.

Have you determined how low the oil was and where it went?
 
   / Engine rebuild or troubleshooting advice
  • Thread Starter
#7  
By my memory, the oil was barely registering on the dip stick. I assumed it "burned off" based on reading about the different colours of smoke. When it was lugging and stalling the day it overheated the smoke was really black. So I thought that what I was doing was running it too hot and burning off oil. But I have no idea.

Since that episode I've been checking the oil and coolant every time before I start it. The coolant hasn't leaked since, and the oil doesn't appear to burn up. But I also don't run it past 190, I shut it off. Everyone seems to think that's operating temp, but I think it will just overheat and start stalling again, maybe not. Next time I run it I'll see what happens if I just keep going a little bit when it's at 190.

Thanks for the advice. Does anyone happen to know a good place to find parts other than a dealer? Sometimes they don't carry parts and my internet searching hasn't resulted in any good places yet. I think I need a radiator now after my last fiasco.
 
   / Engine rebuild or troubleshooting advice #8  
What's the oil pressure like?
Does it start quickly when cold?
Do you know the reason for the temp gauge installation?r

If it starts well then get the rad fixed properly, pull the head & check things out. Take the head to a shop for fluxing and planing if nessisary. Or go for a rebuild at a competent shop.
 
   / Engine rebuild or troubleshooting advice
  • Thread Starter
#9  
What's the oil pressure like?
Does it start quickly when cold?
Do you know the reason for the temp gauge installation?r

If it starts well then get the rad fixed properly, pull the head & check things out. Take the head to a shop for fluxing and planing if nessisary. Or go for a rebuild at a competent shop.

I don't know how to check the oil pressure, I'll have to read the manual :)
When it's cold outside it wouldn't start, I installed a block heater, then it started fine. When it's late spring and summer it starts on the first try no problem.
I never got to talk to the actual previous owner, there was a medical issue, but I assume the guage was an improvement over the "idiot light" on the 755.

So now I have to learn how to check compression and oil pressure after I get another radiator and install it.

Thanks,
jasen
 
   / Engine rebuild or troubleshooting advice #10  
Diesel engine and black smoke go Hand and hand. If you had white or blue smoke I'd be more concerned. You say you were tilling. How big is you tiller, they pull harder than you think. When is the last time the air breather/filter was cleaned or replaced? This can cause one to smoke if it is gtrying plugged. Engine running at 190 to me isn't to bad. If it starts running 205-210 or more I'd start worrying. If I working my old allis Chalmers with a cast block I don't worry near as much as my compact with an aluminum block.(cast will take a lot more). Also you should have a screen in front of the radiator. If the screen gets plugged up with grass clippings and just about anything floating in the air, that can cause it to hear up. Keep that screen clean and occasionally hose the radiator out with a garden hose while engine is turning about 1000 rpm. I'd maybe change the thermostat make the water pump in good and play with it. If you cracked the head or blew the head gasket I would think you would have water mixing with the oil, an engine that is hard to start, and or power issues. Yanmat should have engine parts. Hope this helps.
 

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