M5700 'Knock' and other questions

[mangus580]

My father picked up a M5700 this weekend. Overall its in nice shape, but we have a couple things we are trying to figure out.

Most importantly, it has a 'knock' to it, that doesnt sound like a rod knock, but is something that does need attention, and we arent quite sure what it is. Seller had suggested it was likely an out of adjustment rocker arm. today I took the valve cover off and checked all the rockers, found one slightly out of spec, but it did not cure the problem. Since it was still making the noise, i ran it some with the valve cover off, holding each rocker tight against the valve, and then the push rod, testing to see if I could alter the noise. it had no effect.

The next thing i tried, was cracking each injector to try to isolate it to a cylinder (and maybe also an injector). On cylinders 1-4, it seemed to have no effect on the noise. #5 it did sound like it went away mostly (if not all the way, its hard to tell for sure)

I dont suspect a rod bearing issue, as they usually have some variation with RPM. This is very consistent.

Here is a video of it running and the noise is very clear in the video: Kubota M5700 'knock'? - YouTube

Looking for ideas! Tractor has just under 2000 hours on it. I drove it home (almost an hour drive) and it ran fine, has plenty of power etc. I am seriously thinking maybe a bad injector? or worse, maybe a piston pin? It does sound more top-end than bottom-end in the engine. We did pour some fuel injector cleaner (diesel kleen brand) and ran it for probably 45 minutes doing light duty loader work after. No change. he is thinking possibly a collapsed lifter?? and is planning to try some Rislone in it to see if that helps. I would think a collapsed lifter would be obvious with the valve cover off (especially when running!)

Other questions....

The tire sizes seem off. The rear has 16.9-24 on it (R4 industrial tires). I cant remember what the fronts are at the moment, but I believe they were on a 20" rim??

Where might I find a drawbar for it? it is among the missing, and is something we really could use. Also could use some 3pt inserts, as the ones on it appear to have been broken and re-welded? or at the least bent? The angle on them seems odd.

We are missing a couple other things that would be nice to put back on, like the mirrors (both inside and out), and it seems to have maybe had a dome light inside the cab?

Final thing... what RPM is this supposed to idle at? Seems a bit high if you ask me....


Thanks
Mike

 

[Agvg]

Would start with a test on the injector, it may be leaking.

 

[rbargeron]

Hi Mike,

The engine in this rig is nearly identical to the 5-cyl F2803's I've had in a L4150 and two L5450's.
These engines have very good build quality and problems are rare/

I'd try using a mechanic's stethoscope, probing all over the engine for
where the noise is loudest, and go from there.

To isolate one cylinder, loosen the nut on its fuel pipe to drop the pressure.

 

[mangus580]

Well.... it was not an injector....

Isolating a cylinder indicates its possibly in #5... but really hard to say.

With the stethoscope, we are almost considering a bolt backed out in the bell housing? or too long of a bolt put back in during an oil pan re-installation? Its confusing. I drove the tractor home from the place he bought it... right about an hour straight down the road. If it was something that was going to be catastrophic... it likely would have happened already!

It has us mystified... with the scope, it almost appears loudest right at the bell-housing above or right at the starter??

Open to more ideas!!

 

[rScotty]

Well.... it was not an injector....

Isolating a cylinder indicates its possibly in #5... but really hard to say.

With the stethoscope, we are almost considering a bolt backed out in the bell housing? or too long of a bolt put back in during an oil pan re-installation? Its confusing. I drove the tractor home from the place he bought it... right about an hour straight down the road. If it was something that was going to be catastrophic... it likely would have happened already!

It has us mystified... with the scope, it almost appears loudest right at the bell-housing above or right at the starter??

Open to more ideas!!

Sounds like you are a pretty good mechanic. I listened to the noise, and agree it doesn't sound like a rod knock....it's a little too light of a noise. It does sound like an upper end noise, and my first thought would be valve adjustment and the second is something in the valve train or combustion cylinder. But you checked most of that pretty well. Does the M5700 have hydraulic lifters that could collapse? I thought that most diesels used solid lifters....but I don't actually know.

When I'm being a mechanic, I don't mind pulling out the old "parts shotgun" & using it for diagnosis IF the part is inexpensive and has other benefits, and I'm otherwise stumped. With that philosophy in mind, I think I'd replace #5 injector. It's your best bet & simple to do so you have to eliminate it. It could be as simple as an injector sticking or spraying just enough to put that cylinder a few degrees out of ignition timing versus the others, and that would cause the #5 piston skirt to slap.

The other thing it might be is it is in the right years to have an EGR valve. The Kubota EGR assembly hangs off the side of the block back by the last cylinder on the 4 cylinder machines. On engines that have them the Kubota EGR is kinda complex. It has an a rather large valve inside that looks like an engine valve. It opens by by magnifying the exhaust gas pulse on a diaphramand, and closes with a coil spring. I've heard the EGR rattel at some RPMs, and especially when carboned up. Frankly though, the EGR rattle is a lighter sound than what I hear in your video and more like a rattle than the sound I hear there. Still, worth at least looking at. That is a part you probably can use a stethoscope on.
...
By the way, I like to use the stethoscope, but can't remember that it has ever led to a diagnosis. Fun though.

I don't think it is a bolt. It sounds like engine noise. Try the injector.
rScotty

 

[mangus580]

The saga continues....

So we put a new injector into it. Actually, took the one from cyl 3 and put it in 5... then put a new one in 3. (put the new one in an easy to get to spot)

No change....

The noise almost totally goes away when cracking the injector on #5.

so... today we decided to pull the oil pan, thinking we could check for a bad rod bearing, wrist pin, etc.

We found nothing wrong.

I am starting to suspect possibly the injection pump now????

I cant think of what else could possibly make this noise!!

 

[rScotty]

Well, that's actually a lot of good news. Unfortunately it sounds like it's not the injector, but that was a decent guess and not expensive.
Not finding anything obvious with the pan off is another piece of good news. BTW, we used to pull oil pans and then lightly tap on the bottom end of each rod with a small hammer. The offending cylinder would sometimes sound different....not always. The trick was to use a very small hammer - like ringing a bell.

As to what else could it be? You did mention that the noise was loudest close to the starter - and that you thought it might be a loose bolt.
I didn't think it could be a bolt, but then my idea for the #5 injector didn't find the problem either. So maybe time to take another look around the starter.

If you are looking for the next thing to try, if it was mine I'd back up and say OK, maybe it really is something in the starter. Wouldn't that be nice! That would also be really rare, but it is easy enough to look at. On most motors the starter is about the easiest thing to take off and there are still starter/alternator shops in small towns.

One possibility there is iIf the bendix spring on the starter is broken then it makes sense that the starter pinion could kind of float back and forth on its shaft and might rattle against the flywheel.
Also, does your M5700 have a manual dry clutch? If so, there are bolts that hold the clutch together and yes, I guess one could come loose. Also rare, but anything's possible with mechanics. And with the starter off you can see a little bit into the bell housing. Maybe even snake a little magnet down beside the flywheel toward the inside bottom of the bellhousing and see if you pick up anything.
I think that those mechanic's inspection cameras on a flex shaft with a screen are cheap enough now that Home Depot carries them. I think I saw them there. That might be worth looking into.

Hmmm... Clutch or not, every motor does have a bellhousing. Does that bellhousing have a drain plug in the bottom? Some do.
A bell housing drain That would be another place you could stick a magnet or inspection camera into and have a look.

Does yours have the EGR valve? They can rattle too. If it has EGR, that can be disabled for a test by simply clamping shut the 1/4" dia. rubber hose that leads from the thermostat back to the EGR valve on the right side rear of the motor. I doubt that's it, but only takes 30 seconds to test.

But at this point I think I'd pull the starter off.
luck,
rScotty

 

[sd455dan]

The saga continues....

So we put a new injector into it. Actually, took the one from cyl 3 and put it in 5... then put a new one in 3. (put the new one in an easy to get to spot)

No change....

The noise almost totally goes away when cracking the injector on #5.

so... today we decided to pull the oil pan, thinking we could check for a bad rod bearing, wrist pin, etc.

We found nothing wrong.

I am starting to suspect possibly the injection pump now????

I cant think of what else could possibly make this noise!!

Wondering if it could be something like happened in an earlier thread
where a staple?
somehow got into the intake tract and got embedded into the piston top

Made for a pretty good knock.

If an inspection camera could be fit into the injector hole - might reveal something, since rod bearing play / bad injector does not seem to be the culprit.

 

[Agvg]

The bad thing is that it almost go away when you realease the fuel pipe, by doing that you can ignore error in the fuel system, checked valve clearance and movement? Compression test?when you run it, are exhaust bend out of the problem cylinder colder than the other cylinders?

 

[hawkeye08]

I've got a new engine noise on my Kubota L3130 that seems to have started since I started getting diesel at Costco (locally new Costco was built and they have diesel), it can have up to 5% Biodiesel if I recall correctly... it changed sound last Saturday, I also changed the oil this spring, noise started after that.. my hearing is not as good as it once was so harder to hear certain sounds.. it is also running a bit rougher, I will likely get fuel somewhere else next time and see if it makes any difference.