Overheated Tractor - Where to start

[oldmech]

My opinion! First I remove the head and send it for check (Flatness , leaks and cracks etc) AFTER RESULT If head is Ok! If your motor was taking oil you can remove pistons . I HONE the cylinders and put new rings and same time you check Connecting rod bearings clearance with Plastic gauge. Head gasket and rings are not very expensive and you have a new motor for a long time.
Good Luck ! Oldmech

 

[SailorBob]

I finally got around to opening up the engine. I pulled the head and dropped the oil pan. That was quite a job! Anyway, The head looks okay. I did not find anything apparently broken or bent. I am going to take it to a machine shop to be tested. If there is no major damage I will have the valves and seats done too. The number 2 piston is a diffent story. It looks like the piston may have melted on the upper edges. I found pieces of metal sitting on top of the piston. (see pics) Also, I can't really even see the rings. I am sure they are cooked. Hopefully, if the head is okay i can get away with replacing the rod bearings, #2 piston, and rings on both.

Hopefully, the crank and mains are okay. There was plenty of oil in there and it looks like most of the heat was in the pistons.

Does anyone have any suggestions?

 

[California]

Bob, I'm sorry to see what happened there. I don't have any suggestions, just couple of comments:

That's #1 cylinder by Yanmar's definition. They number the cylinders starting from the flywheel. (This can be a source of confusion when you rotate the engine to adjust the valves at TDC.)

Is there any chance that the loose metal in the cylinder is from a foreign object that was sucked into the cylinder and then dented the piston? That would be a less serious scenario compared to a melted piston.

Also, the original warning light will come on when there is no water in the upper hose connector, at least on my similar YM240 (YM2000.) One of several problems caused by the previous owner was that the new genuine Yanmar lower radiator hose (previous owner's repairs) developed a leak where the sloppy-loose new fan belt (installed by that previous owner), chewed a pinhole leak in it. I lost enough water to trigger the warning light a couple of times in the first couple of days, before I fixed it.

I guess I do have one suggestion: since the pistons are coming out, have you considered replacing the pistons and sleeves as a matched set?

 

[oldmech]

OK! Now I see your goods pics . I think you MUST remove Pistons for check Wall cylinders FOR CRACKS (AT the top cylinders walls If any Very bad Need new block. FOR DEEP SCRATCHS) ( We can remove lights smalls scratchs in honing process). If any deeps scratchs you can change sleeve (if your motor have) or rebore cylinders and put news pistons and rings. We can change one sleeve and piston but we must rebore the two cylinders and put news pistons and rings (expensive). You must evaluate the cost before begin. Good luck! Oldmech

 

[SailorBob]

Bob,
That's #1 cylinder by Yanmar's definition. They number the cylinders starting from the flywheel. (This can be a source of confusion when you rotate the engine to adjust the valves at TDC.)

Is there any chance that the loose metal in the cylinder is from a foreign object that was sucked into the cylinder and then dented the piston? That would be a less serious scenario compared to a melted piston.

Also, the original warning light will come on when there is no water in the upper hose connector, at least on my similar YM240 (YM2000.) One of several problems caused by the previous owner was that the new genuine Yanmar lower radiator hose (previous owner's repairs) developed a leak where the sloppy-loose new fan belt (installed by that previous owner), chewed a pinhole leak in it. I lost enough water to trigger the warning light a couple of times in the first couple of days, before I fixed it.

I guess I do have one suggestion: since the pistons are coming out, have you considered replacing the pistons and sleeves as a matched set?

California,

Thanks for clarifying the cylinder numbers. I replaced the overheat light with a temp gauge. The temp sensor was bad. Looks like the temp gauge does not work without being in contact with water either.

I have moved the pistons up and down and the liners appear to be in good shape. I could not see or feel any scratches. I know that I can replace the cylinders and pistons as a set. I just hate to keep putting money in this old tractor. The sleeves are nearly $200 each plus $90 each for the pistons. You get the idea. If the block is cracked I may just junk it.

I just don't know where the metal came from. I did discover an interesting thing while removing the head. There is supposed to be a gasket around the bottom of the breather where it is clamped to the flange. Well, there was. A homemade piece of inner tube that did not wrap completely around the flange. There was about a 1/2 inch gap. It had it had to have let a lot of debris into the intake. The intake was very dirty . The shade tree's that so called reconditioned this tractor did a fine job.

The metal is very soft. Looks a feels kind of like solder.

 

[SailorBob]

OK! Now I see your goods pics . I think you MUST remove Pistons for check Wall cylinders FOR CRACKS (AT the top cylinders walls If any Very bad Need new block. FOR DEEP SCRATCHS) ( We can remove lights smalls scratchs in honing process). If any deeps scratchs you can change sleeve (if your motor have) or rebore cylinders and put news pistons and rings. We can change one sleeve and piston but we must rebore the two cylinders and put news pistons and rings (expensive). You must evaluate the cost before begin. Good luck! Oldmech

Oldmech,

Thanks for your reply. The engine is sleeved. Maybe this weekend I can remove the pistons, and, check cylinders and block. A new block will probably push the cost of rebuilding the engine out of reach. Also, I don't have a garage or even a concrete pad to work on it from. I don't think I could split the tractor in the yard. Also, if I have to pay a mechanic to do the work it cetainly will.

 

[BTDT]

Bob, I have a Ford 1300 2 cyl. diesel that we rebuilt about 4 yrs ago, cost around $2000.00. This was taking the rebuilders the engine, they bored, new everything, including clutch and pressure plate. Ours was not sleeved. You may come out cheaper.

 

[CATMAN]

On older CAT engines that use fuel injection nozzles(direct injection); you must change the nozzles if the engine ever got that hot. The press-fit between the nozzle tip and the nozzle body loosens up during the extreme overheat and that tip will blow out into a newly overhaul engine after you start it up and run it under load for a while. I just bring this issue up, so you can ask an old Yanmar mechanic to see if this issue exists with your engine. You don't want a second failure immediately after an expensive overhaul.

Also, do the cylinder walls look like a mirror finish OR do they show any cross-hatch left on the cylinder walls?​

 

[john_bud]

California,

Thanks for clarifying the cylinder numbers. I replaced the overheat light with a temp gauge. The temp sensor was bad. Looks like the temp gauge does not work without being in contact with water either.

I have moved the pistons up and down and the liners appear to be in good shape. I could not see or feel any scratches. I know that I can replace the cylinders and pistons as a set. I just hate to keep putting money in this old tractor. The sleeves are nearly $200 each plus $90 each for the pistons. You get the idea. If the block is cracked I may just junk it.

I just don't know where the metal came from. I did discover an interesting thing while removing the head. There is supposed to be a gasket around the bottom of the breather where it is clamped to the flange. Well, there was. A homemade piece of inner tube that did not wrap completely around the flange. There was about a 1/2 inch gap. It had it had to have let a lot of debris into the intake. The intake was very dirty . The shade tree's that so called reconditioned this tractor did a fine job.

The metal is very soft. Looks a feels kind of like solder.

Sailor,

You may have sucked some solder in. The ahem - mechanics- ahem that did the work on your machine may have soldered a gap or done some other goofy thing.

I couldn't really see the pictures very well. Focus is out too much. You may try and use a nylon bristle brush to clean the top of the piston and see how it really looks. There is also some spray you can use to remove carbon. Can't hurt nothing at this point and you may find that you don't need a new piston.

jb

 

[Soundguy]

To complicate matters.. if this is a 4 -digit 'grey' yanmar under a 2000 series.. it won't have a water pump.. just thermosyphon. Thus the top end may have gotten hotter thant he bottom.. as there would be no water above the level in the radiator with no circulating pump going.

I agree witht he other advice.. drop the pan and check out a bearing.. then have a looksee at the valvetrain..

soundguy

I have seen many,many cases of temp. gauges and computer temp. sensors not registering properly when the system is out or almost out of coolant. When there is no liquid coolant in the system, the water pump isn't pumping anything - it can't pump air or steam. Don't know about the Yanmar but most engines have their coolant sensors very near the exit from the engine, just before the thermostat, and this is usually at the top of the engine, hence one of the first areas to lose contact with the dwindling coolant level. For a little while the coolant may be high enough for steam coming off it to reach the sensor, but as the level decreases, the sensor will start reading cooler.

As far as the engine goes, I would suspect the head gasket right away - fill system with water & pressure check it. If it was hot enough to cook the paint, the rings are surely toast. There's a slight chance the knocking could be caused by water getting into a cylinder - or it could be crankshaft related. Water in a diesel can actually bend or break a rod. The pressure test should pinpoint your water leaks - might have to remove the injector(s) to check in the cylinders for water.