I have a 2016 L3901 that started knocking a couple weeks ago. I've run it several times and after a while of running under load, it will just bog down and die. Tey to crank and turns over real slow and won't crank. Let it cool down for a while, from 15 minutes to 1 hour, and it will crank right up again, only to repeat dieing after a while. Heard from a mechanic that it's spun a rod bearing on the crankshaft. I know it has a lot of hours (1350) but not sure this is definitely the answer. Looking for some input as I'm not keen on giving them $5k to rebuild the engine. Any help is appreciated.
Knocking 3901
- Thread starter timlee
- Start date
Gee, my first thought was that it spun a bearing. This is not a good thing as the piston can contact the head and bend a connecting rod. I will tell you 1350 is NOT a lot of hours for that tractor. It should have easily gone double or triple that unless it was run low on oil or lacked oil pressure. I'm unfamiliar with that specific tractor but if you can drop the oil pan you can check the rod bearings easily enough. If you have spun one you will probably have to have the crank turned to repair it correctly. THAT'S where the big bucks come into play.
I would think if you spun a bearing the engine would be locked up by now.Cooling off and starting again sounds more like seizing a piston. Something I find for too often is gas instead of diesel. The engines run extremely hot for a short period of time. Let them cool off and they will run again.
I suspect a bad rod bearing. I strongly recommend you don’t run it because this could lead to a broken rod coming through the block. Now your looking at a new engine.
Cut open the oil filter and look for metal. If aluminum it is the piston(s) if bearing and ferrous material it is crankshaft related.
As stated 1350hrs. is not much at all. Most likely due to a lack of lubrication.
As stated 1350hrs. is not much at all. Most likely due to a lack of lubrication.
I agree with the above posters. Nothing good will happen if you continue to run it 
I'm not familiar with your tractor but if you can drop the pan what is laying in there may tell you a lot.
I'm not familiar with your tractor but if you can drop the pan what is laying in there may tell you a lot.
whitetiger
Moderator
Staff member
Equipment
Kubota tech..BX2370, RCK60, B7100HST, RTV900 w plow, Ford 1100 FWA
A spun bearing will not bog down killing the engine and releasing it when it cools. You have a piston seizing in the cylinder bore. Have you checked your coolant level? Do not just look at the surge bottle, remove the radiator cap and look in the radiator.
What are you using for the fuel filter? If you are using one of the "It will screw on" after-market cans that are not a small enough micron, you may have trashed an injector that eroded a piston.
Well, I appreciate your responses. I've found out now that it had a small hose on the bottom of the radiator disconnected, unaware that all the coolant was gone and temp indicator didn't show hot. Now, with that said, expect knocking sound was caused by overheating. What's the harm in running it now that I've got it full of coolant?
try it and see. The loss of coolant shouldn't have had any wear to the bearings. If you still have knocking or seizing then you'll have to tear it down and fix the damage.
whitetiger
Moderator
Staff member
Equipment
Kubota tech..BX2370, RCK60, B7100HST, RTV900 w plow, Ford 1100 FWA
The temp gauge could not show engine temp because there was no fluid touching the sender.
The damage is already done, the knocking is caused because at least one piston was seizing in the cylinder bore. When you remove the cylinder head, you will find one or more of the cylinder bores scored, and the piston deformed.
If you keep running it, it will probably eventually break a connecting rod which will knock a hole in the side of the block.
Just did that with the Cummins in my Dodge truck. Pushed it too hard up too many steep grades in a row, and it blew all the coolant out. I pulled over as soon as I heard it start to knock, let it cool down, added water, and it started right up. But, there was a bad knock coming from #5 or #6. Melted piston. As soon as I had a chance, I pulled the cooling system thermostat out and threw it over my shoulder. I think it was leaking around the water pump gasket (just a rubber O-ring). Or, the thermostat might have not been opening. I tested it in a pot of boiling water, and the passage rate (low) was no different at boiling temp than it was when cool. Also replaced the water pump, for good measure, and got it sealed properly by cleaning up the mounting surface with a wire wheel. I've driven the truck more than 1000 miles since then, but I realize I'm on borrowed time.
Now, it knocks something fierce when I start it up, but after the engine is warm, the knock becomes much quieter. Of course, without the thermostat it takes 1/2 hour of run-time to warm up. Doesn't seem to lack much power...And, it will run all day without getting hot, as long as I keep coolant in it!
Not to worry, I have a line on a couple of used short blocks, each for $2000. The engine I just killed was bought 9 years ago, out of the mud at a junkyard, for $1500. Knew nothing about its past history. That was at least 100,000 miles ago...
-Paul
PS, I used to drive Chrysler flathead-powered vehicles. When replacing the thermostat, I always added a couple of bypass holes to it with a 1/4" drill bit. Just for safety.
Now, it knocks something fierce when I start it up, but after the engine is warm, the knock becomes much quieter. Of course, without the thermostat it takes 1/2 hour of run-time to warm up. Doesn't seem to lack much power...And, it will run all day without getting hot, as long as I keep coolant in it!
Not to worry, I have a line on a couple of used short blocks, each for $2000. The engine I just killed was bought 9 years ago, out of the mud at a junkyard, for $1500. Knew nothing about its past history. That was at least 100,000 miles ago...
-Paul
PS, I used to drive Chrysler flathead-powered vehicles. When replacing the thermostat, I always added a couple of bypass holes to it with a 1/4" drill bit. Just for safety.
Last edited:
yeah just keep running it. At some point it will just quit. And then you have options. Option #1, replace the engine. Option #2, replace the engine AND the plugged DPF assembly, as the cylinder being overheated/damaged will cause seizure, which then causes low compression and/or oil usage. Low compression situation on common rail engines means that the injector is still dumping fuel into it, it ain't burning it, so it goes right out the exhaust...into the DPF. Oil usage meaning, the engine will pump oil pas the rings and plugs up the dpf with oil. Both situations, a lot of them you can't clean them, you just have to replace em.
last time I looked at an engine and DPF R&R on an L-01 series, it was close to 20 grand including labor. KTAC deal; and they totaled it. Did have to R&R one, no insurance, real close to 20 grand with DPF and labor. Maybe they've come down since then.
if it's been that hot, the cylinders and pistons are damaged. Guaranteed. Now I know some guys will say run a hone through it and toss a set of piston kits in it and send it, but these engines are really sensitive to bore taper and egging. There is a service limit for both, and it ain't much-and every single one of them that I've been into that was overheated required bore/hone to bring them back to "square". I've run into a few that were "rebuilt" as such (dingleberry hone and an amateur rebuild), and those were the ones that would have a frequent regeneration cycle and/or required dpf replacement later on down the line.
last time I looked at an engine and DPF R&R on an L-01 series, it was close to 20 grand including labor. KTAC deal; and they totaled it. Did have to R&R one, no insurance, real close to 20 grand with DPF and labor. Maybe they've come down since then.
if it's been that hot, the cylinders and pistons are damaged. Guaranteed. Now I know some guys will say run a hone through it and toss a set of piston kits in it and send it, but these engines are really sensitive to bore taper and egging. There is a service limit for both, and it ain't much-and every single one of them that I've been into that was overheated required bore/hone to bring them back to "square". I've run into a few that were "rebuilt" as such (dingleberry hone and an amateur rebuild), and those were the ones that would have a frequent regeneration cycle and/or required dpf replacement later on down the line.
It is normal for a diesel with a melted piston!
The tailgate on my Dodge is getting continually preserved from the blow-by!
But, I'm only losing about a quart every 700 miles.
-Paul
The tailgate on my Dodge is getting continually preserved from the blow-by!
But, I'm only losing about a quart every 700 miles.
-Paul
