How much sludge is a Kuboto D750 likely to have

[MaxW]

Are the Kuboto D750 Diesel's any more likely to build up oil sludge then any other engine, or is it purely a lack of maintenance by the previous owners? I changed the oil a couple months back of the 443B and the speed that the oil drained from the hose was rather slow. The oil was black and dirty, but the thickness was what you would expect for dirty oil. It wasn't thick like molasses. After putting the new oil in and running it the new oil went black rather quickly. At that time I wasn't sure if the slow flow rate out the drain hole was normal or if there was something blocking the hose inside the engine. I recently drained the oil again, the same thing, slow coming out the hose. Pouring some clean oil in and watching it drain out black tells me there is sludge, the question is how much. I've seen some high mileage car motors that you could flush a million times and you wouldn't get the build up cleaned out. The only real way to clean them was to take the engine apart. I will try flushing the pan with solvent(engine off) and shot of compressed air back through the hose to dislodge anything that might have gotten stuck in there and see if that helps. The machine is a 1993 and the hour meter was stopped when we got it. Is it likely the flushing will clean out the pan or should I plan of pulling the engine in the near future?

 

[Bobcatdan]

Oil will drain very slowly if the engine is not at operating temp. I normally will start draing and do somethine eles. If for some reason I don't warm the thing up, I will let them drain over night. Diesels will turn clean oil black very quick, diesels are simply sooty then a gas engine. A trick I do, is after oil stops coming out, I add clean oil with the drain plug out and put the plug back on when the oil starts coming out clean. I think what you are seeing is perfectly normal.

 

[Tazza]

Oil will drain very slowly if the engine is not at operating temp. I normally will start draing and do somethine eles. If for some reason I don't warm the thing up, I will let them drain over night. Diesels will turn clean oil black very quick, diesels are simply sooty then a gas engine. A trick I do, is after oil stops coming out, I add clean oil with the drain plug out and put the plug back on when the oil starts coming out clean. I think what you are seeing is perfectly normal.

I was going to say the same. Ideally you want to warm the engine up before you drain it, it not only thins the oil out, but it also stirs any potential sludge for it to drain out. This is especially true for small petrol/gas engines. As most don't have oil filters, you warm it up to stir up any crud that is in the sump and it flows out the drain plug.
As Dan pointed out, diesels are dirty, that's why you use a detergent based oil, it helps 'wash' the inside of the engine when it's running.

 

[MaxW]

I was going to say the same. Ideally you want to warm the engine up before you drain it, it not only thins the oil out, but it also stirs any potential sludge for it to drain out. This is especially true for small petrol/gas engines. As most don't have oil filters, you warm it up to stir up any crud that is in the sump and it flows out the drain plug.
As Dan pointed out, diesels are dirty, that's why you use a detergent based oil, it helps 'wash' the inside of the engine when it's running.

So I flushed out the pan by circulating solvent in the fill pipe and out the drain pipe. I used a large coffee tin full of solvent, a small drill pump, some plastic tubing and a fuel filter, just to keep any grit from being circulated back into the engine. I'd circulate the solvent until it was nice and black, then replace the solvent with clean fluid and circulated it in and out of the engine again. After draining the solvent I poured a couple cups of oil into the engine with the drain open until the oil displaced the residual solvent. Refilled it will fresh oil, ran the engine and drove it around for awhile to mix up any of the residual solvent and then drained the oil again and replaced the filter. I was hoping this would clean out the pan, and I think it did clean out a fair amount of sludge, but oil that was no more then 20 minutes oil still drained out looking rather dark. Before refilling I poured a couple cups of clean oil through. The new oil still came out the drain hose as a mix of yellow and black. Well, I tried, but I don't think the oil changes on this little diesel are ever going to look like they do with gas engines.

The picture above is the oil coming out after the engine was flushed and then run for about 20 minutes. The picture below is what fresh oil poured into the engine and immediately allowed to drain out looks like.

 

[Bobcatdan]

So I flushed out the pan by circulating solvent in the fill pipe and out the drain pipe. I used a large coffee tin full of solvent, a small drill pump, some plastic tubing and a fuel filter, just to keep any grit from being circulated back into the engine. I'd circulate the solvent until it was nice and black, then replace the solvent with clean fluid and circulated it in and out of the engine again. After draining the solvent I poured a couple cups of oil into the engine with the drain open until the oil displaced the residual solvent. Refilled it will fresh oil, ran the engine and drove it around for awhile to mix up any of the residual solvent and then drained the oil again and replaced the filter. I was hoping this would clean out the pan, and I think it did clean out a fair amount of sludge, but oil that was no more then 20 minutes oil still drained out looking rather dark. Before refilling I poured a couple cups of clean oil through. The new oil still came out the drain hose as a mix of yellow and black. Well, I tried, but I don't think the oil changes on this little diesel are ever going to look like they do with gas engines. The picture above is the oil coming out after the engine was flushed and then run for about 20 minutes. The picture below is what fresh oil poured into the engine and immediately allowed to drain out looks like.

You are really over achieving. Diesels turn oil black, sometimes as fast as starting the engine and shutting it off to check it.

 

[Tazza]

You are really over achieving. Diesels turn oil black, sometimes as fast as starting the engine and shutting it off to check it.

They always go black, if you changed the oil every 5 or 10 hours you may be able to keep it clean like a petrol/gas engine. It's just the nature of the beast i'm afraid.
Generally you can go by the darkness of the oil, the longer it's in there the blacker it gets. Starts off black but you can still see through it, it will get to the point that you can't see through it and if it touches your skin it gets stained, it's then time to change the oil.

 

[BobCat]

They always go black, if you changed the oil every 5 or 10 hours you may be able to keep it clean like a petrol/gas engine. It's just the nature of the beast i'm afraid.
Generally you can go by the darkness of the oil, the longer it's in there the blacker it gets. Starts off black but you can still see through it, it will get to the point that you can't see through it and if it touches your skin it gets stained, it's then time to change the oil.

Diesel engine oil runs black most of the time no if ands or buts about it. I'm running Auto RX in my 743B to clean up any sludge lying around inside. After about 50 hrs I'll drain the oil and replace the filter and do it again. Then I plan on running a smaller amount with every oil change there after for maintenance purposes. For the worry wart that should give you some piece of mind.

 

[MaxW]

Diesel engine oil runs black most of the time no if ands or buts about it. I'm running Auto RX in my 743B to clean up any sludge lying around inside. After about 50 hrs I'll drain the oil and replace the filter and do it again. Then I plan on running a smaller amount with every oil change there after for maintenance purposes. For the worry wart that should give you some piece of mind.

Thanks for the info. I won't worry about it, I'll change the oil regularly, and just accept that is the way these engines are. Thanks.