L2900 smoking and knock?

[Black Dog Chainsaw]

My L2900 is smoking from the down tube not the exhaust. It also has a fairly noticeable knock when cold. Smoke seems to be whitish in color and is constant even when engine is hot. Engine was 2qt low on oil when I changed it and the tractor had only been mine for 1 month. Threw some seafoam in the diesel to see if that cleans the injectors and cleans out the smoking issue. The coolant tank was pretty dry but wasn't overheating and the oil light wasn't on. I topped off coolant and changed the oil too. No run time yet on oil change and coolant top off.

Am I looking at head, cylinder, or bottom end? Any ideas????


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[85Hokie]

you got a bad case of blow by.....if caused by bad rings, it should improve somewhat as the pistons heat up and expand - you say it is still doing it warmed. You have bad rings or worse,

the knock I imagine is with rpm? you mentioned bottom end - any oil pressure gauge on this machine? 2 quarts low, not a good sign,

run it and allow it to get nice and hot and see if any of it improves......the smoke might but the knocking is there to stay......

 

[North Idaho Wolfman]

Pull the valve cover and run it, if it smokes out of the block holes then it's the rings, if it smokes out of the valve stems then it's the head.

 

[kuboman]

Sounds like you are burning antifreeze and possibly it is leaking into the crankcase as well. Probably have a cracked head or blown head gasket. But it could be worse than that. Need to pull the head and start there.

 

[rbargeron]

Knocking and white smoke are indicators of water getting into a cylinder. Run it without the valve cover like Wolfman suggests. After that, a look under the head might be in order. Taking off the head is a reasonably easy job and it will let you see the condition of the gasket, valves, & cylinder bores. Then you can decide where to go from there. Might just need a head gasket - but while the head is off take it to an engine shop and get it trued flat. Kubota's iron heads are very robust - they will warp a little but cracked ones are not common. Good luck, Dick B

 

[Black Dog Chainsaw]

Thanks guys. The knocking is most noticeable at low rpm idling when cold. The smoke gets a little better when warm but still more than I would like.

I've rebuilt v8 engines and hundreds of chainsaws so this thing looks easy enough. I can't have it blow apart this winter as it's our only snow removal unit for a 1/4mile long driveway!

I read a place or two that these L2900's like very frequent oil changes. Like every 50-75hrs... True?

Also heard the air filtration isn't the best. I kinda need it for the next 2-3 weeks and then plan to take it into my shop for maintenance before winter. I assume 15/40 rotella oil is fine and if I keep it and the antifreeze topped off I should be ok for a few weeks of use?

Any commonly known problems with this series? Doesn't seem like a diesel should have these problems at 2000hrs!!!!


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[ShaunRH]

Thanks guys. The knocking is most ...

Any commonly known problems with this series? Doesn't seem like a diesel should have these problems at 2000hrs!!!!

2000 hrs is enough to show poor maintenance. That's about equivalent to 70,000 miles on a car. If the unit did not have its oil changed regularly, (every 80-100 hours or so) it can wear prematurely. If it never had its oil changed, you'd actually have really bad wear on the rings and cylinder walls by this time.

Because the units are in hours, it tends to throw people a loop on maintenance cycles, also some folks out there go "It's a diesel tractor, it doesn't need maintenance like a car does" and so they neglect the tractor. A rough guess for miles to hours is to multiply the hours by 35 (which is the average speed a car tends to travel over its lifetime in miles per hour). Going by those numbers, that tractor should have had its engine oil and filters changed 24 times if you were using car metrics for changing the oil.

 

[Black Dog Chainsaw]

Yea hours might tend to throw people off but the 20-25hp kubota diesels that are in grasshopper mowers run 2-3k easy without having problems.


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