Kubota B7100 Overhauled now will not run

[Sanddog]

With no water pump or thermostat you should be able to flush water both ways thru the engine and radiator.
Hopefully a Flush either way may indicate a problem area. Just curious, have any frost plugs been changed?

I believe the machine shop did put in some new freeze plugs in the block after the bored and vatted it.

The head came new from KumarBros and already had freeze plugs installed. Obviously, there was an overheating problem before I bought the tractor, thus the new head I mention. I ran a lot of water through the radiator and did not seem to be any restrictions, at least not that I could tell. I washed the radiator fins alot with water and do not now recall that it was terribly choked up with trash. I will blow the fins out this weekend with an air compressor just to make sure there are no issues there, but the radiator is not hot anyway, just at the top. I was wondering if the tractor should have a fan shroud? There is not one on there now and I have not noticed any attachment points.

 

[Egon]

The should would help but leave that till the coolant flow is solved. If no flow thru the complete engine it will be pull head again time and determine if it is the head or block.

The previous owner may have had a freeze plug fail and overheated the motor?

Please note I am not a mechanic and making some assumptions.

Keep the Faith and with peresverance you will prevail!

 

[deanocraft]

Are you saying the radiator does not get hot? I assume the engine has a thermostat like a gas engine... Could that be a problem?

 

[Sanddog]

Are you saying the radiator does not get hot? I assume the engine has a thermostat like a gas engine... Could that be a problem?

The radiator gets very hot but just at the top, does not seem to spread across the entire radiator after a short run but still hot at the top.

Actually, this little tractor does not have a thermostat, nor a water pump. It also does not have a fan shroud, but it should. After looking at pictures of other 7100s online, it looks like someone removed the fan shroud at some point. I ordered a new one, as I think that may have at least something to do with the heating problem.

I pulled the radiator back off and ran water through the block/head both ways and there is not an indication of any blockage. I also ran water through the radiator and it flows freely. I did observe that the oil cooler is in pretty bad shape and is unlikely to allow much air flow through it. I think that combined with the missing fan shroud are a definite problem.

I next checked the injection timing and found that is was five degrees off. Best I could tell by carefully watching for any indication of fuel moving at the pump, it was starting to inject at 20 degrees BTDC instead of 25 BTDC as indicated in my repair manual. I reduced the shim pack just slightly and got it pretty much right on at 25 degrees BTDC. Possibly this also could be contributing to the overheating??

After the new fan shroud arrives, I will anxiously put the radiator back on and see what happens this time.

Anyone know where to get a good aftermarket replacement for the oil cooler? A new Kubota oil cooler is over $400. It is pretty small cooler and I can see no reason it should cost anywhere near what they want for a new "factory" cooler.

 

[Leejohn]

I'm going to throw this at you. It seems like to me the way the cooling works and if there is any back pressure the water flow would stop. I would check and make sure some one didn't put the wrong radiator cap on it. You might try it with cap loose or without one.

 

[Egon]

Boys oh boys, what a conundrum. At this point alli can do is offer encouragement.

Probably the only factor on the oil cooler would be pressure rating. With size there should be room to attach some where in front of the rad.

 

[deanocraft]

No water pump? I'm at a loss... Sorry to sound confused, but I can't figure out how the coolant will circulate without a pump. To me, the description you gave sounds like the hot water is not circulating. It is only staying in the top of the engine and the top of the radiator, with the cool stuff at the bottom... Wouldn't that make for a hot head?

 

[aczlan]

No water pump? I'm at a loss... Sorry to sound confused, but I can't figure out how the coolant will circulate without a pump. To me, the description you gave sounds like the hot water is not circulating. It is only staying in the top of the engine and the top of the radiator, with the cool stuff at the bottom... Wouldn't that make for a hot head?

They were designed to be a Thermosiphon system and so the heat from the engine causes the coolant to circulate.

Aaron Z

 

[bigdeano]

The radiator could well be operating normally. My Isuzu diesel generator radiator will run at 170 deg at top of radiator and bottom tank will be room temperature. That's what they're supposed to do, cool the water. Does the cylinder head get too hot? Couldn't find it in your posts.

 

[KYErik]

If the coolant is not boiling/making a rumbling sound when it finally dies, I don't see why it would be seizing up because it is too hot. There is a lot of friction as new piston rings first wear against a freshly honed cylinder- and yes things will get tighter as the engine warms up.

Does this injection pump have a governor that functions at idle? I know diesel injection pump governors work well at maintaining engine speeds regardless of load, but I am not knowledgeable enough to know how effective they are at idle. I believe that maybe the engine is just being bogged down by all the friction (and slightly rising temps/increased friction) and the current amount of fuel injected to keep the engine at a slow idle isn't enough to keep it running. If it was mine, I would run the engine at 25% throttle the next time I started it and see exactly what happens when it dies (does it bog down slowly or quickly die just as you pulled the engine kill knob).

Leave the rad cap off and kill it at the first sign of steam if you are afraid to get it hot (the pressure behind the cap raises the boiling point).

Maybe even crack an injector line and make sure it is still leaking as the engine dies (to make sure the injection pump isn't losing prime or malfunctioning).

 

[powerscol]

"Anyone know where to get a good aftermarket replacement for the oil cooler? A new kubota oil cooler is over $400. It is pretty small cooler and I can see no reason it should cost anywhere near what they want for a new "factory" cooler. "

Any good radiator shop can rebuild you unit, replacing what needs to be replaced - check around.

 

[Sanddog]

The radiator could well be operating normally. My Isuzu diesel generator radiator will run at 170 deg at top of radiator and bottom tank will be room temperature. That's what they're supposed to do, cool the water. Does the cylinder head get too hot? Couldn't find it in your posts.

Yes,the cylinder head does get hot. I have a fitting ordered so I can installed a temp gauge in the top radiator hose to see just hot it is actually running.

 

[Sanddog]

If the coolant is not boiling/making a rumbling sound when it finally dies, I don't see why it would be seizing up because it is too hot. There is a lot of friction as new piston rings first wear against a freshly honed cylinder- and yes things will get tighter as the engine warms up.

Does this injection pump have a governor that functions at idle? I know diesel injection pump governors work well at maintaining engine speeds regardless of load, but I am not knowledgeable enough to know how effective they are at idle. I believe that maybe the engine is just being bogged down by all the friction (and slightly rising temps/increased friction) and the current amount of fuel injected to keep the engine at a slow idle isn't enough to keep it running. If it was mine, I would run the engine at 25% throttle the next time I started it and see exactly what happens when it dies (does it bog down slowly or quickly die just as you pulled the engine kill knob).

Leave the rad cap off and kill it at the first sign of steam if you are afraid to get it hot (the pressure behind the cap raises the boiling point).

Maybe even crack an injector line and make sure it is still leaking as the engine dies (to make sure the injection pump isn't losing prime or malfunctioning).

I do not hear any rumbling or signs that it is trying to boiling over. I am a little gun shy on too many attempts to keep it running if it seems to want to seize up. My neighbor has the same tractor but is out of town. I am waiting for him to return in a week or two so I can observe his running to see how hot it gets and how the temp dissipates across the radiator (hot only at top or across the entire face).

There is a governor but it is all internal and I cannot see how it is working.

I will make another run at is just as soon as I can see how things should perform based on my neighbor's tractor.

Thanks for the suggestions.

 

[JohnnyFbomb]

Any updates?

 

[Sanddog]

Any updates?

UPDATE

Last time I had put it all back together and built a small engine stand to attempt starting it while separated from any possible "downstream" source of resistance based on the recommendation of the guy at the machine shop. They had rechecked all clearances after I had torn it back down after the initial attempt to run it after the overhaul. Initially it would run maybe 20 seconds to 30 seconds before appearing to get hot and stop running. After putting it all back together and in the process getting the timing gears aligned correctly (think I had crank shaft off one cog when I put it together the first time) it ran for what seemed liked a few minutes (did not time) before it appeared to get hot and die. Thinking I had it right this time, I put the engine back on the tractor and checked the injection timing. The injection pump was set up like it came to me, but appeared to be off 5 degrees. I adjusted the shims until it appears to be right on based on the very first indication of injection at 25 degrees BTDC on the front cylinder. I had also noticed it was missing the fan shroud, so I bought one of those and installed it along with a temp gauge in the upper radiator hose this morning.

My neighbor has the same tractor, so I had him run his at idle for 3 minutes so I could see how hot his appeared to be getting and how the heat was moving across the radiator. After running for three minutes, the head was pretty hot but I could put a finger on it briefly without too much discomfort. The radiator was hot at the top only, similar to what I have observed on mine.

This morning, I was finally ready to try it again. Bleed the fuel lines, filled the radiator and fired it up. It idled very smoothly, with no smoke. There was just a little smoke when I would accelerate, which is normal per the manual. It ran fine for two minutes and began to show a hint of smoke and then died. I was showing about 45 psi oil pressure the entire time and the temp gauge only got to ~120 degrees. I had left the radiator cap off and no bubbles or any other unusual observations. The head was hot, such that I could not hold a finger on it. Not scientific, but did seem to be hotter than my neighbors tractor after his ran for three minutes. I looked everything over, started it up and it ran for about one and a half minutes and then appeared to bog down and die.

I am really at a loss, as it seems to be running perfectly but then appears to get hot and try to seize up. It never has boiled over and the temp gauge never got above 140 degrees, although head seemed hotter than that to the touch. I am wondering if it could be running too lean and getting hot??? I have not checked the injection pump but the tractor has about 2600 hours, so I guess it could be worn and causing a lean condition. Anyone have any experience with this??

 

[JohnnyFbomb]

I had a perkins that did the exact same thing as you are talking about. Rebuilt the pump, and it was fine. All diesels runs fuel lean. But if you have smoke sometimes, that's a good sign. Have you checked pressure of the lift pump? Are there any fuel sieve screens in front of the lift pump? It could be lazy and not supplying fuel to IP. It sounds like you have the engine worked out, and it's a fuel issue now. I would rip that injection pump off and have it run on a flow bench just for peace of mind. Also, it's a new engine, it's going to run hotter as everything is so tight right now.

 

[Sanddog]

I had a perkins that did the exact same thing as you are talking about. Rebuilt the pump, and it was fine. All diesels runs fuel lean. But if you have smoke sometimes, that's a good sign. Have you checked pressure of the lift pump? Are there any fuel sieve screens in front of the lift pump? It could be lazy and not supplying fuel to IP. It sounds like you have the engine worked out, and it's a fuel issue now. I would rip that injection pump off and have it run on a flow bench just for peace of mind. Also, it's a new engine, it's going to run hotter as everything is so tight right now.

Thanks, I cannot think of anything else to try. I am obviously not a diesel mechanic, so I am not familiar with the effect of problems that may come from a bad injection pump.

 

[KYErik]

Here's something that you could do to test whether it was really seizing up. Turn the crank pulley bolt with a torque wrench with the engine cold and record the max amount of torque needed for 2 revolutions. Start the engine and run it until it dies and repeat the test right after the engine dies to verify that the engine is not seizing up.

If it shows no signs of seizing up, I'd run it some more and try to crack an injector line to see if it still gets fuel as it dies.

 

[kevinj]

Thanks, I cannot think of anything else to try. I am obviously not a diesel mechanic, so I am not familiar with the effect of problems that may come from a bad injection pump.

Are you saying that you done a complete rebuild without having the pump and injectors serviced?????????

 

[Sanddog]

Are you saying that you done a complete rebuild without having the pump and injectors serviced?????????

I installed new injectors purchased at Kubota. I have not done anything with the pump, but it does not give any sign of starving for fuel.