Komatsu D31P-16 Engine rebuild.

[FurakawaMatt]

I have a '81 Komatsu D31 that has a fair amount of blowby. Still has good power and does not smoke. However I catch about a cup of oil a hour of running that has blowned by the Ventilation tube. At the moment I just filter and add it back to the engine. Bit of a hassle and probably not the best practice but it works.

My question is does anyone have an idea of what I could expect in terms of cost of having the engine rebuilt? Since the dozer is not used commercially the hours it gets are few but I hate to have things not working right. Thanks to anyone that has any answers.

 

[Tinkerer]

It is impossible to give you any kind of cost estimate. There are too many variations to consider. I can list a few. Are you going to do the rebuild yourself or have a rebuilder do it ? Will it be an inframe overhaul or will the engine be removed ? A simple valve grinding job on the cylinder head or a complete remanufacture (new valves, springs,guides and seats). Just a new set of piston rings or a major overhaul kit with new sleeves and pistons including rings. Will the crankshaft need a simple polish job or be reground ? Perhaps even replacement depending on the condition it is in.
New camshaft bearings ? New camshaft and valve lifters ? New oil pump ?
Don't forget about determining if the fuel injectors need servicing and or replacement.
The engine has to be taken apart. Then you will know what the extent of the repairs that will be needed. After doing that a list of those repairs and their costs can be determined.

 

[FurakawaMatt]

Thanks Tinkerer for your response. I realize that a actual estimate would take knowing all that you say. Not interested in that as much as a ballpark figure for a standard rebuild from normal wear by somebody qualified to do it. It is a very simple engine without blowers or turbo so not much to it. I do not know if such a thing as re-manufactured engine is available for swap out. Since it runs now, I do not think things like fuel injectors, new camshaft, oil pump (blows oil now) or lifters. It probably simply needs the cylinders and piston rings replaced.

Without knowing a idea of the costs it is hard to plan for whether it is worthwhile to repair and to save money to do it. Of course once the engine is opened who knows what might be found? But even a complete rebuild will have a upper limit to cost. So knowing a range is helpful as well.

 

[Tinkerer]

The blowby could caused by worn out pistons and or rings. Also worn out valves and guides. Most likely a combination of all four things. You could take a gamble and do a simple cylinder head rebuild only. If you still have an amount of blowby that is too severe to live with , then you would have to repair the short block in depth. If you just do the head you would only be out the price of a valve grind set of gaskets and your time if that doesn't fix it.

 

[FurakawaMatt]

Thanks once again for the information. What do you think a diesel mechanic would charge to do what you mention? I imagine that the dozer would have to be moved to his repair area. Though I can handle minor mechanical things I am no mechanic. Sure I could take the engine apart and put it back together, but I lack the understanding of what would need repair by looking at it. Experience in those things is everything.

 

[Tinkerer]

I have no idea as to what a diesel mechanic would charge. Perhaps if you posted that question in the shop talk section you may get an answer. I have always done repairs of this kind myself. Actually I just completed a major overhaul to the engine of my own tractor/loader/backhoe.

 

[John C.]

As far as the oil in the breather I have to wonder if you simply have a blown head gasket. I have not seen ring and cylinder wear in these engines unless someone used lots of ether, overheated the motor, dusted it by not changing air filters, did not change oil often or ran it out of oil. In my experience something breaks before they wear out.

To give you an idea of where to look for costs associated with rebuilding the engine you should first call the Komatsu dealer parts department and ask if they have exchange engines and what the costs are.

They way the industry is structured today, particularly with Komatsu, is that the cost of the reman is about what it would cost you in parts to rebuild yours. That will just be the start of your research. You also have to figure removal and install time, freight costs, machining costs and fluids. Your engine does not have liners so you are all but required to do a bore and hone with installing oversize rings.

The mechanic time for just rebuilding the engine is around sixty hours give or take. R&R time is around twelve hours.

 

[willie59]

I have a '81 Komatsu D31 that has a fair amount of blowby. Still has good power and does not smoke...

Since it runs now, I do not think things like fuel injectors, new camshaft, oil pump (blows oil now) or lifters. It probably simply needs the cylinders and piston rings replaced.

I'm like John C, those engines almost have to be abused to wear out the pistons and rings. If it starts good, runs good, doesn't smoke bad, I'm inclined to wonder if something else is causing the blowby.

 

[FurakawaMatt]

Thank you very much for the information! A head gasket replacement is within my capabilities and might be worth a shot. I have had a blown head gasket in a diesel engine before but it was noticeable by the white exhaust smoke from coolant getting into the exhaust. Plus a major hit to power and operation. However if the place of failure was by a exhaust port that could put pressure to push oil out. Thanks for the idea.

 

[hthunder]

Thank you very much for the information! A head gasket replacement is within my capabilities and might be worth a shot. I have had a blown head gasket in a diesel engine before but it was noticeable by the white exhaust smoke from coolant getting into the exhaust. Plus a major hit to power and operation. However if the place of failure was by a exhaust port that could put pressure to push oil out. Thanks for the idea.

I do not know how far you are from Caruthersville, Mo. but this is one of the best head rebuilders around and very resonable. I had the same issues as you on my D3B and a head rebuild cured the problem. I had a blowed head gasket and the valves guides were leaking bad. You can mic the cylinders for wear when you pullo the head. I had the head off of mine in less than 2 hours.

Barnett Head & Block Co
101 East 6th Street, Caruthersville, MO 63830-1605

Good Luck

 

[FurakawaMatt]

Thanks for the recommendation. I am over on the NW side of Arkansas so I will look around to see if there is someone closer to me to get the head rebuilt. What did your head rebuild run you in the terms of cost? I think it is likely that if I go to the effort of pulling the head it should get rebuilt before reinstalling.

 

[rudaluda]

I've been thinking of an engine rebuilt and there cannot be a more informative thread than this one.

 

[hthunder]

Thanks for the recommendation. I am over on the NW side of Arkansas so I will look around to see if there is someone closer to me to get the head rebuilt. What did your head rebuild run you in the terms of cost? I think it is likely that if I go to the effort of pulling the head it should get rebuilt before reinstalling.

The cost on the head was #345.00.I can't remember the cost on the gaskets. It was a pain to go back in and retorque the head bolts after I had run it a few hours but I did not want to run the risk of not retorqueing. Sure made a different in starting and the power.

 

[FurakawaMatt]

Thanks hthunder for the information! It looks like a good Fall project for me to get done.

 

[rudaluda]

rebuilt engines

Thanks Tinkerer for your response. I realize that a actual estimate would take knowing all that you say. Not interested in that as much as a ballpark figure for a standard rebuild from normal wear by somebody qualified to do it. It is a very simple engine without blowers or turbo so not much to it. I do not know if such a thing as re-manufactured engine is available for swap out. Since it runs now, I do not think things like fuel injectors, new camshaft, oil pump (blows oil now) or lifters. It probably simply needs the cylinders and piston rings replaced.

Without knowing a idea of the costs it is hard to plan for whether it is worthwhile to repair and to save money to do it. Of course once the engine is opened who knows what might be found? But even a complete rebuild will have a upper limit to cost. So knowing a range is helpful as well.

lol no doubt

 

[chevydiggs]

Hi all, im new to the forum and have already found some useful stuff on here, looks like a very nice place. I cant post yet cause of my new status so found a thread already started close to my same dozer, i have recently purchased a Kumotsu D31P-16, seems to be a nice machine so far, i pinched a hose in my track adjustment spring and ended up having to replace it caus the hose was rotten but after replacing the hose i purchased a 5 gallon bucket of hydraulic oil to top off reservoir, havent ran but maybe 5 mins after repair to check hose and was looking on here and now im not sure if i should have used hydraulic oil or something different, please let me know and if its ok to leave that fluid in or what, also wanted to know if there was a dipstick somewhere else for the hydraulic fluid or if the sight glass on under right arm rest was only level indicator and should it be in middle of glass? thanks

 

[FurakawaMatt]

According to my operators manual the hydraulic fluid is CD SAE 10 W. Since that is not the most common stuff in my neck of the woods, I have been using Heavy Duty Tractor Hydraulic and transmission fluid. The level Bubble should show fluid in it about mid way up.

 

[chevydiggs]

Ok, thanks, do you think its ok to stay with the hydraulic fluid or should i get some of the dual purpose hydraulic/transmission fluid?

 

[PonyExpress94]

To the Original Poster, I am in the position of needing to rebuild the engine in my 1987 Komatsu D21E-6 Dozer. I believe my engine is one engine family smaller than the one in your D31. The machine shop that I will use once I get the engine out has given me a rough estimate of $4-5k for a complete rebuild. This does not include removal and reinstallation as that will be my responsibility. I also will not need new injectors as I had them pop tested and they are well within spec. The injection pump has not been tested yet so that is an unknown variable still. FYI, I would suggest doing a search on Google for the Model Number of the engine family used in your D31. I was able to come up with some remans that were available and prices were listed, so this may help you budget for this job you plan to undertake.

 

[FurakawaMatt]

Thanks for the information PonyExpress94. I am still waiting for Fall here to start with pulling the head. Hope your repair goes good and your injector pump does not need fixing.