Hi, i have a Komatsu D41A-3, any ideas on this Horrendous rattle? its from in motor (not radiator fan) it was puffing quite a bit of smoke out of valve cover breather (and oil top up when caps removed) no metal shavings on dipstick, it had a complete rebuild around 10 years ago and has probably only done 50ish hours since then. I took valve cover off everything from eye looked ok. Ive seen other diesels with same sound with bad injector, i tried cracking off each one but made no difference to noise. I bought a cheap oil pressure gauge which got no reading, and with sender bolt removed (on back of oil filter) no oil even come out when it was running, would this be showing a bigger problem rod broke or similar? Thanks
If there's no oil pressure thats it for that motor . Have you just bought the dozer ?
If you run that engine anymore your going to be able to stuff a basketball through the side of the engine block. That is a connecting rod hammering, time for the engine to be pulled.
lack of oil pressure indicates major problem. con-rod bearings usually fail first when oil pressure is lost due to them being supplied by oil via drillings in the crank coming from the main bearings. in other words, they are the last to get oil flow and therefore usually the first to fail. spun main bearings usually don't make nearly as much noise as a failed(spun) rod bearing. what you are hearing is the rod hammering on the crankpin as it changes direction(up and down). if it is loose, the piston may also be hitting the head at TDC which usually also causes a knocking, hammering noise. no magic or cheap fix for this one. will require a complete bare-block rebuild if not excessively damaged or another engine. a bare-block rebuild may involve major block repair and machining as well as one or more new rods and maybe even a new crank. existing crank may be able to be reground but likely not. some rods may be able to be re-sized on the big end. and then there is the assessment of initial failure causing the loss of oil pressure which could be a number of things. what is the condition of the rest of the machine? is it going to be worth fixing? can you repair it yourself or will you have to hire it done? all questions that have to be considered
Thanks for replys, Damn kind of what i was expecting though. We have owned it 25 years been a great dozer and everything on it is still in very good condition so would really like to fix it. I can probably pull motor apart and get someone more experienced to put back together, would rather go replacement but the market is very small in New Zealand so i dont think that will be an option. As i said was rebuilt 10ish years ago so surprised its happened, What do you think could be a couple main reasons for this happening so i know what to look for when pulling apart?
If this engine only has 50ish hours, I would look at the fit of the bearings and condition of the oil pump. Who rebuilt the engine and what type of rebuild was it? There are several definitions of rebuild that are quite different. There is more experience on this forum than you will find there, in my opinion. Do you have the type of tooling to do this on your own?
I agree that the motor needs to come out and be torn down. The smoke and type of sound leads me to think a broken ring on a piston. I had something like that happen on a D8 years ago when the owner went cheap on rebuild groups. They weren't factory parts and the top ring was broke which didn't show up till about 100 hours after the machine was put back in service. Pull the engine oil filter and cut it open for confirmation. A broken rod bolt failure will usually show silver and copper colored particles in the bottom of the canister. I have to agree with Vetech63 on the meaning of rebuilt being a variable term.
hey guys bit of an update have pulled motor out and sump off, well yip was the rod hammering. the 1st rod closest to flywheel gears etc I have pulled the cap off, the bearing is completely gone, but its perfectly smooth on cap and everywhere that i can feel on crankshaft and cap. should this not be a bit banged up? whats the chances of just slipping another bearing in there? and Vetech was a complete rebuild id assume as cost $14K NZD i would have to get dad to dig out the invoice as its been so long i cant remember anything but the price
The only way to know for sure is to clean that journal and mic it. It really depends. If you caught it early enough it may just take a good cleaning. I have had bearings fail that didnt tear the journal up, but welded bearing material to that journal. You have to be careful when cleaning it off. You need to find why the bearing failed. Have you removed the other caps and inspected those bearings? I would be contacting the company that did the job. A quality rebuild should not have done that.
Usually when a rod bearing goes away the bear rod will wear the crank journal egg shaped not round . But the good side is you stopped before the block got ruined. Bob
I dug a bit deeper and found the cause, one of the gears in the oil pump has broken a tooth off. Vetech i removed a couple other bearings I don't really know what I am looking at if they are ok or not i have attached pics (all other bearings and journals were coated with oil so i hope thats a good thing) Also at a closer look the Journal with the failed bearing when comparing to the other journals is not that great, has a few pits etc in it have also attached a pic, i guess this is something that will need attention? could this not be run as is? what i am worried about is if there not enough material to have someone grind it i dont know if i will be able to find another crank in New Zealand And lastly can a engine stand be bolted to these bolts on back of the motor? specs show motor weighs 620kg, would a 900kg stand be ok i just havent seen anyone use them for these bigger motors
I had a couple teeth break off on my oil pump gear and lost oil pressure on a rebuilt engine with 16 hours on it. Shop checked oil pump out and it met specs. but said from then on they will always replace the oil pump. I heard a noise and saw no oil pressure so shut it off right away. Thankfully they covered it on warranty but I had to pull the engine and trans. back out as a unit. I joked if it had to come back out again they would do it.... It was going through too much oil and had no smoke at all. They said to put 500 hours on it to break it in but it still went through oil. I paid $300 to get it taken to their shop (and back to my property) where they pulled the engine and repaired it again on warranty. They said for some reason the rings didn't seat. It was worth $300 to have them to pull the engine and trans. back out instead of doing it in a field with no shop to work in.
Looks like your going to need a crank grind.
The crankshaft will require attention or replace and the flywheel housing has to come off to pull crank, Bob
If the crank cannot be reground on that throw, and a reasonably priced crank can't be found, a specialty crankshaft shop may be able to weld it up and grind it back down. It appears as though it is already reground by the 0.50 stamp on the old shell. That would likely indicate .5mm undersize which would be .020" What are the remaining available undersizes if any, for that engine? On an oil starvation failure, usually the bearing farthest from the supply fails first
hey thanks for the info all this is new to me was wondering if thats what the .5 resembled , i did notice in the parts book bearings listed as .25, .5, .75 . so hopefully the next size will work. The bearing that failed was actually the 1st one, closest to the oil pump which i though was weird. the furthest one still had a good coating of oil on it.
thats why i said usually . maybe the big-end bore of the rod was at the top end of the bore spec and got loose and it spun the bearing on that throw before the others. hard to say. i'm assuming the rods were re-bushed and resized on the big end. if not, they should have been. it should have said if they were on the original repair order