Kubota L4740 Engine "knock" Help?

[jshwhite]

I'm back, and we're making progress. Honed the cylinders yesterday with a dingleberry hone and got a nice crosshatch on the cylinder walls. Got the crank mains on, crank installed, pistons in and rods attached. All torqued down. Next up is putting balancer shafts, valve cam, fuel cam etc. And I have a question..maybe a dumb one??

Supposed to set 4th cylinder to TDC on compression stroke, then put all the shafts in and line up the timing marks on the gears. But how do you know whether it's on compression stroke or exhaust? There's no cam in, no valves (no head). Does it not matter? Just set the 4th at TDC and when you put it all together with timing marks aligned it becomes the compression stroke? Sorry if that's a dumb question. Thanks!

 

[dodge man]

I would say it doesn’t matter. With no cam in the rest of the engine wouldn’t know if it’s compression or exhaust. Once the cam is in that would determine it. Keep in mind I’m not sure of my answer but it makes sense.

 

[TMGT]

You've got it right, cam determines what stroke its on, so set piston to tdc and install cams.

 

[ruffdog]

Cam runs 1/2 crank speed so half the time it is comp stroke, half is exhaust.

 

[jshwhite]

Thanks guys. Yeah that makes sense. I guess for extra security one could just make sure the lobes are down on the cam for cylinder #4. But I think if all the timing marks line up it should be correct.

 

[jshwhite]

Made some more progress this afternoon. Everything went smoothly.

To put all the shafts and gears in, first set cylinder #4 to TDC,
- Slide the balancer shafts in. Put the mounting bracket and torque those, as there's one bolt hidden behind the cam gear.
- Slide the cam in and line up the timing mark to the balancer shaft.
- Install the fuel cam.
- Bolt/torque the idler gear mount, then slide the idler gear in, lining up all timing marks.

Note: make sure to put the valve tappets in BEFORE the head. I almost forgot and was just about to torque the head down.

I forgot to put the tappets in order of how they came out, and noticed it said in the service manual not to swap them around. Oops. Hopefully since it's a pretty new engine it won't matter. I'll double check all the valve clearances before running it.

Note 2: There's a little lever (governor??) that's part of the fuel cam assembly. When you put the injection pump in, you have to push it back out of the way of the rack pin on the injection pump before you bolt it down. See the pic with the red arrow. I missed that and tightened it down with that lever under the pin. It bent the lever but thankfully I was able to straighten it out.

Hoping to get it all back together in a few days here. Will be nice to be able to blow snow!!

 

[dodge man]

It’s coming along. I went back and reread this thread, I had forgotten some of the history. Do you have an opinion on what caused the problem.

 

[jshwhite]

It’s coming along. I went back and reread this thread, I had forgotten some of the history. Do you have an opinion on what caused the problem.

Well, as best I can figure, something caused an oil starvation issue on the front end. Basically every bearing toward the front end was at least somewhat worn. The main crank bearing took the hardest hit for some reason, and the resulting vibration destroyed the gears, which caused yet more damage. The question of course is what caused the oil starvation? I don't know. All the oil passages were clear as best I could tell.

I suppose it's possible that something messed the gears up, and as they self-destructed the pieces made their way through the system and destroyed the bearings, as well as causing some oil starvation from clogging. But that doesn't make complete sense because it was the front bearings that were worn. General oil starvation would affect the entire engine, not just the front. And what made the gear get messed up to begin with?

I guess it's hard to say which came first, the chicken or the egg, but in my opinion the oil starvation issue came first.

Would love to hear ideas from others on here.

 

[rScotty]

Well, as best I can figure, something caused an oil starvation issue on the front end. Basically every bearing toward the front end was at least somewhat worn. The main crank bearing took the hardest hit for some reason, and the resulting vibration destroyed the gears, which caused yet more damage. The question of course is what caused the oil starvation? I don't know. All the oil passages were clear as best I could tell.

I suppose it's possible that something messed the gears up, and as they self-destructed the pieces made their way through the system and destroyed the bearings, as well as causing some oil starvation from clogging. But that doesn't make complete sense because it was the front bearings that were worn. General oil starvation would affect the entire engine, not just the front. And what made the gear get messed up to begin with?

I guess it's hard to say which came first, the chicken or the egg, but in my opinion the oil starvation issue came first.

Would love to hear ideas from others on here.

I would like to see a lubrication diagram for this engine. Do you have one? My assumption is that engine oil under pressure is forced everywhere that there is a passage open under approximently the same pressure. It's a fairly low pressure at best - in the 20 to 50 psi range I'd guess. So I realize that pressure doesn't mean flow is happening.
And from what you've seen it does sound like something starved the front of the engine. So the first guess would be something clogging the oil passages to the front.

But you've checked that path to the front. So could it be that one of the other oil pathways passages suddenly opened up too much for some unknown reason and all of the oil flowed to the easier path?

Here's a thought....If all the oil was being forced to flow in a low resistance path, wouldn't it show as an overall drop in oil pressure on the gauge?

If true, then I think that I'd be tempted to see if I could put a couple of extra pressure taps into various places in the oil flow.... and maybe some extra gauges. They don't cost much. And then keep a close eye on them for awhile. Keep in mind that most taper tapped holes in Kubota blocks (oil & water) are British Tapered Pipe Thread rather than Metric or SAE. That's so common with Japanese engines that most hardware/auto stores have the required thread adapters.
luck,
rScotty

 

[TMGT]

Well, as best I can figure, something caused an oil starvation issue on the front end. Basically every bearing toward the front end was at least somewhat worn. The main crank bearing took the hardest hit for some reason, and the resulting vibration destroyed the gears, which caused yet more damage. The question of course is what caused the oil starvation? I don't know. All the oil passages were clear as best I could tell.

I suppose it's possible that something messed the gears up, and as they self-destructed the pieces made their way through the system and destroyed the bearings, as well as causing some oil starvation from clogging. But that doesn't make complete sense because it was the front bearings that were worn. General oil starvation would affect the entire engine, not just the front. And what made the gear get messed up to begin with?

I guess it's hard to say which came first, the chicken or the egg, but in my opinion the oil starvation issue came first.

Would love to hear ideas from others on here.

I'd tend to lean towards either something going through those gears or the gear failing and a tooth/teeth jamming between the gears.
The high pressure of that could damage/deform the front bearing enough to allow excessive clearance and essentially pound itself lose. This could also explain the excessive wear on the adjacent main bearings, partly from excessive play but also from reduced oil pressure from the extra clearance in that front bearing.

Thats my theory at least, its hard to tell from a few pictures online, but I have seen foreign material take out timing gears before, however in those instances the valve timing was thrown off enough that the engine shut down preventing further damage. The bearing journals did show signs of damage from the high forces of the gears, even from just the initial damage and the engine spinning down.

I'm also curious about the oiling circuit, being that the pump is front mounted I'm guessing that the 1st or 2nd main is getting fed first and mostly likely it has priority main oiling system.

 

[dodge man]

I assume there is an oil passage in the crank? I assume that was clear.

The gas engines I worked on in classic Mopars had the oil pressure sensor at the top back of the block. It was the rear cam bearing that would starve first if you had low oil pressure. I know if the engine was badly worn to much oil would leak out the lower bearings and that cam bearing would starve. This would take an engine to be mostly shot to happen. Without looking at your Kubota engine I don’t know how it’s fed, but I would agree those front bearing are probably close to the beginning of the oil circuit. Like you say if the previous owner had let it run low on oil you would think you would see damage elsewhere. Could also be some kind of factory defect.

 

[jshwhite]

I wish I had an oil flow diagram, but I haven't been able to find one.

TGMT, your explanation actually makes the most sense to me. Perhaps it wasn't actually a starvation issue as much as just the fact that if the gears got messed up then the extra vibration/pounding caused wear on the front end, along with reduced oil pressure.

rScotty, good thought on the oil pressure gauge. There is no oil pressure gauge on the dash (maybe a warning light if the pressure drops too low?) I actually was wondering about putting an aftermarket gauge on it. Anyone here done that? And yes, dodge man, the sensor is at the top back of the block.

 

[goeduck]

What was the blinking warning light for on the original video again?

 

[rScotty]

I wish I had an oil flow diagram, but I haven't been able to find one.

TGMT, your explanation actually makes the most sense to me. Perhaps it wasn't actually a starvation issue as much as just the fact that if the gears got messed up then the extra vibration/pounding caused wear on the front end, along with reduced oil pressure.

rScotty, good thought on the oil pressure gauge. There is no oil pressure gauge on the dash (maybe a warning light if the pressure drops too low?) I actually was wondering about putting an aftermarket gauge on it. Anyone here done that? And yes, dodge man, the sensor is at the top back of the block.

I thought my M59 shop manual would have an oil flow diagram for that same engine, but it doesn't. Surely we can find one, though. Anyone have access to Kubota tech dept?

On other engines I've put gauges on by just finding the oil pressure warning light sender on the block, unscrew it and replace it with a brass "T" fitting. The warning light sender gets put into one leg of the T, and a good gauge sender in the other leg. You might want to do the same to the temperature sender....why not? $60.00 will buy all the adapters and a good quality high resolution set of temp & pressure gauges as well.

rScotty

 

[jshwhite]

What was the blinking warning light for on the original video again?

Just an error code for a cruise control something or another.

I thought my M59 shop manual would have an oil flow diagram for that same engine, but it doesn't. Surely we can find one, though. Anyone have access to Kubota tech dept?

On other engines I've put gauges on by just finding the oil pressure warning light sender on the block, unscrew it and replace it with a brass "T" fitting. The warning light sender gets put into one leg of the T, and a good gauge sender in the other leg. You might want to do the same to the temperature sender....why not? $60.00 will buy all the adapters and a good quality high resolution set of temp & pressure gauges as well.

rScotty

Good idea. I'll have to add that to the list.

Made good progress today and got the case bolted back together. The only hitch was those governor springs from the throttle body to the fork lever (in the injection pump housing area of the block). They're a royal pain to put back on. They kept falling off the throttle body lever and I dropped one, had to take the gear cover and fuel cam back out to get it. Best plan is to take off the engine stop lever housing and hold your finger against end of the spring on the throttle body lever to keep it from coming off, then take a pair of needle nose with your other hand and hook the springs on the fork lever.

Other than that everything went smoothly. Hopefully will get some time tomorrow afternoon and get it all back together.

Perhaps I should do a writeup on splitting the case and tearing the engine down. If I can find the time...

 

[jshwhite]

Does anyone know what the recommended break-in procedure is for these engines? Hoping to fire it up this evening. If I understand correctly, long idle times are not good during break in. The challenge is that I don't have a heated shop and it's 30 degrees. I guess I could put a torpedo heater aimed at it for an hour or so before starting it.

 

[pmsmechanic]

As far as I'm concerned long idle times are not good at any time. Too much unburnt fuel washes down the cylinder walls and into the oil.

Warm it up slowly and cool it off slowly. I would keep a close eye on the temperature gauge and put a garbage bag in front of the rad so you can make sure the engine gets warm. Only fold over enough of the garbage bag to keep the engine at operating temperature or a bit above.

 

[crazyal]

I think Kubota just recommends running the engine at around 1300 rpm to warm it up, not idle. Other than that I wouldn't put a load on the engine (other than the usual hydraulic load) until it starts to warm up and the oil has had plenty of time to circulate. If you have a block heater I would use to to warm the engine up (if it's kept outdoors).

 

[LD1]

You need to step up your game. Only 14 pages for a blown engine:laughing:

Do you believe in "misery loves company"?

https://www.tractorbynet.com/forums/parts-repairs/402625-blew-up-kubota-motor.html?highlight=

In the end, I just bit the bullet and spent the $7500. Wasnt worth the risk. But mine had a spun balance shaft bearing in the block....and no oversized ones offered.

I was looking at $4k plus to rebuild mine......or $6k plus for a reman (with no turbo). Just couldnt justify all the what-ifs lingering in the back of my head. New with warranty was the only logical decision I could make.

But curious....how much $$$ do you figure you will have in your repair? And did you even consider new? Yours might have been a tad cheaper for being a non-turbo 2403.

Glad it looks like you dodged a bullet and were able to rebuild. But TRUST ME.....I feel your pain

 

[jshwhite]

As far as I'm concerned long idle times are not good at any time. Too much unburnt fuel washes down the cylinder walls and into the oil.

Warm it up slowly and cool it off slowly. I would keep a close eye on the temperature gauge and put a garbage bag in front of the rad so you can make sure the engine gets warm. Only fold over enough of the garbage bag to keep the engine at operating temperature or a bit above.

I think Kubota just recommends running the engine at around 1300 rpm to warm it up, not idle. Other than that I wouldn't put a load on the engine (other than the usual hydraulic load) until it starts to warm up and the oil has had plenty of time to circulate. If you have a block heater I would use to to warm the engine up (if it's kept outdoors).

Thanks. Yeah, I guess when I said "idle", I was more referring to low-rpm in general. But it has to warm up, so I'll just try to do so as quickly as possible. From what I've read, you want about 10-15 hrs of varying rpm light-duty use, then work it hard for another 10-15hrs. Does that sound right? I gotta find some way to work it hard here in the winter...guess I could hook a couple of heavy logs to it and drag them around.

You need to step up your game. Only 14 pages for a blown engine:laughing:

Do you believe in "misery loves company"?

https://www.tractorbynet.com/forums/parts-repairs/402625-blew-up-kubota-motor.html?highlight=

In the end, I just bit the bullet and spent the $7500. Wasnt worth the risk. But mine had a spun balance shaft bearing in the block....and no oversized ones offered.

I was looking at $4k plus to rebuild mine......or $6k plus for a reman (with no turbo). Just couldnt justify all the what-ifs lingering in the back of my head. New with warranty was the only logical decision I could make.

But curious....how much $$$ do you figure you will have in your repair? And did you even consider new? Yours might have been a tad cheaper for being a non-turbo 2403.

Glad it looks like you dodged a bullet and were able to rebuild. But TRUST ME.....I feel your pain

You bet misery loves company! I needed some this afternoon trying to get those steel hydraulic lines back in. Crazy jigsaw puzzle...and you have to do them in the right order or you'll end up taking the ones off you just put on. Ask me how I know.

I don't envy you. That $7500 hurts thinking about it. Yeah I was fortunate here that the block wasn't damaged too much and was able to just fit new bearings.

I considered new, but I'm cheap I had about $700 in parts and another $400-500 in fluids and a few odds and ends. New with warranty would be nice, but I figure worse comes to worse I'll just be back where I started in another 350 hours. And I'll be able to do it faster next time! :laughing: Hopefully that won't happen though.


Didn't get as far as I hoped this afternoon. The devil is in the details. So I guess startup will be tomorrow...