Yanmar 2500 frankensteined

[Uncle_Charlie]

I bought a YM2500 to brushhog my property. It runs fine, the hydraulics work fine, but it's not exactly a YM2500. The front half is 2500, and the back half is YM3000. The seat is from a Murray riding mower. Somehow, it all works together just fine despite being built from parts of other tractors.

I am confused by the cooling system. The 2500 is not one of Yanmar's tractors that used a thermosyphon cooling system. It has a water pump, but no thermostat. I keep seeing reference to the 2500 being identical the JD850. The JD850 uses the same 3T80 engine, but a different water pump backing plate that accommodates a thermostat.

I'm confused by the design. What is supposed to keep it from overheating? Without any interruption to the coolant flow, even a new radiator won't be doing much to dissipate heat. It pushes coolant into the overflow tank and pulls coolant back into the radiator as needed. So the cooling system is working at some level. But that doesn't change the fact that I can turn off the engine and hear coolant boiling in the block. Hence, my concern and confusion.

 

[careyo63]

I'm familiar with this having a used a 2500. I went and looked and correct. No Thermostat showing in my Yanmar parts. I knew the 2000 didn't have one either. But! the YMG2000 does have a Thermostat. The 2500/2000 Temp. sending switch about it. Test the Pressure in the Radiator sounding like a bad Head Gasket. You can Rent one at most any parts store.

 

[bmaverick]

I bought a YM2500 to brushhog my property. It runs fine, the hydraulics work fine, but it's not exactly a YM2500. The front half is 2500, and the back half is YM3000. The seat is from a Murray riding mower. Somehow, it all works together just fine despite being built from parts of other tractors.

I am confused by the cooling system. The 2500 is not one of Yanmar's tractors that used a thermosyphon cooling system. It has a water pump, but no thermostat. I keep seeing reference to the 2500 being identical the JD850. The JD850 uses the same 3T80 engine, but a different water pump backing plate that accommodates a thermostat.

I'm confused by the design. What is supposed to keep it from overheating? Without any interruption to the coolant flow, even a new radiator won't be doing much to dissipate heat. It pushes coolant into the overflow tank and pulls coolant back into the radiator as needed. So the cooling system is working at some level. But that doesn't change the fact that I can turn off the engine and hear coolant boiling in the block. Hence, my concern and confusion.

This is VERY common to split these two models and yes, they will bolt together and work.

Why is that? Because they both share this attached parts manual.

Compliments of the YTOG,

main groups.io Group

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[bmaverick]

I bought a YM2500 to brushhog my property. It runs fine, the hydraulics work fine, but it's not exactly a YM2500. The front half is 2500, and the back half is YM3000. The seat is from a Murray riding mower. Somehow, it all works together just fine despite being built from parts of other tractors.

I am confused by the cooling system. The 2500 is not one of Yanmar's tractors that used a thermosyphon cooling system. It has a water pump, but no thermostat. I keep seeing reference to the 2500 being identical the JD850. The JD850 uses the same 3T80 engine, but a different water pump backing plate that accommodates a thermostat.

I'm confused by the design. What is supposed to keep it from overheating? Without any interruption to the coolant flow, even a new radiator won't be doing much to dissipate heat. It pushes coolant into the overflow tank and pulls coolant back into the radiator as needed. So the cooling system is working at some level. But that doesn't change the fact that I can turn off the engine and hear coolant boiling in the block. Hence, my concern and confusion.

The YM2500/YM3000 Parts Manual shows,

The YM2610 has he same engine as well,

 

[clemsonfor]

I bought a YM2500 to brushhog my property. It runs fine, the hydraulics work fine, but it's not exactly a YM2500. The front half is 2500, and the back half is YM3000. The seat is from a Murray riding mower. Somehow, it all works together just fine despite being built from parts of other tractors.

I am confused by the cooling system. The 2500 is not one of Yanmar's tractors that used a thermosyphon cooling system. It has a water pump, but no thermostat. I keep seeing reference to the 2500 being identical the JD850. The JD850 uses the same 3T80 engine, but a different water pump backing plate that accommodates a thermostat.

I'm confused by the design. What is supposed to keep it from overheating? Without any interruption to the coolant flow, even a new radiator won't be doing much to dissipate heat. It pushes coolant into the overflow tank and pulls coolant back into the radiator as needed. So the cooling system is working at some level. But that doesn't change the fact that I can turn off the engine and hear coolant boiling in the block. Hence, my concern and confusion.

Sure no thermostat can cause something to actually run hotter under certain circumstances but as a whole it shouldn't, it should run normal or even slightly cooler.

I'm just guessing here but I'd say you have a bad head gasket. Maybe not enough to leak water into the cylinders bad enough to cause performance issues but something doesn't sound right .

 

[California]

I'm just guessing here but I'd say you have a bad head gasket.

And if that's not what's causing overheating, then maybe the radiator needs to be rodded out by a pro radiator shop. After 40 years who knows what's in there. The first owner in Asia may have just used ditch water for his seasonal operation.

I assume the radiator fins are clear.

Compression getting into the cooling system should be apparent, looking in with the cap off.

 

[Uncle_Charlie]

I reread my original post, and I didn't make it clear. The radiator is new. The original was weeping a bit when I got the tractor, so I swapped it out for new one as I didn't want to try to salvage a 45 year old radiator when new ones are readily available. The fins were clear while I mowed as I cleared them several times due to the buildup.

 

[Uncle_Charlie]

I haven't posted in this thread for a while, so I figured an update is in order. Just for grins, I looked up the torque specs for the headbolts to see if they had worked themselves loose. Not all were fully torqued to 160 lbs/ft. With that corrected, I tried to start the engine and the engine didn't even try to turn. The solenoid didn't click. The battery was new a few weeks ago and still reads 12.3V, so it's not dead. Digging into the electrical system seemed to be the next logical step. For a tractor that is powered by a mechanical diesel engine, there is an unholy amount of electrical harness hackery hiding behind the cover panels.

What I've done is to bypass almost the entire electrical system. There is the high current positive cable to the starter. Next is the low current wire that goes from the starter to the ignition switch. I replaced the ignition switch and bypassed the wire going from the ignition switch back to the solenoid. I removed the two wires from the clutch safety switch and shorted those together, though that should not even be in the circuit at this point. There is still nothing happening.

There is another thread in in this subforum addressing solenoids that get sticky and fail to work. I'll pursue that next weekend.

 

[bmaverick]

I haven't posted in this thread for a while, so I figured an update is in order. Just for grins, I looked up the torque specs for the headbolts to see if they had worked themselves loose. Not all were fully torqued to 160 lbs/ft. With that corrected, I tried to start the engine and the engine didn't even try to turn. The solenoid didn't click. The battery was new a few weeks ago and still reads 12.3V, so it's not dead. Digging into the electrical system seemed to be the next logical step. For a tractor that is powered by a mechanical diesel engine, there is an unholy amount of electrical harness hackery hiding behind the cover panels.

What I've done is to bypass almost the entire electrical system. There is the high current positive cable to the starter. Next is the low current wire that goes from the starter to the ignition switch. I replaced the ignition switch and bypassed the wire going from the ignition switch back to the solenoid. I removed the two wires from the clutch safety switch and shorted those together, though that should not even be in the circuit at this point. There is still nothing happening.

There is another thread in in this subforum addressing solenoids that get sticky and fail to work. I'll pursue that next weekend.

I don't recall relays on the YM2500. Just a VR and a fuse box.

The torquing down of the headbolts is done in 3 stages for torquing and each stages has a bolt sequence. Its common to find in the Yanmar service manuals and the TM1192 for the 3T80 engine of the JD850 and JD900HC.

There is a starter upgrade available for the 3T80 engines. The old starters use a solenoid and turns at 1.2Kw of power, the newer technology is a OSGR starter and turns at 2.0Kw of power. Best of all OSGR starters draw less power from the battery. It's all done in the gearing. If you have a very old and tired starter, then upgrade.

 

[careyo63]

The YM2500 has a decompression cable. It holds the valves open so there is no compression when you start the motor. Are you using it? Pull it open and then see how easy the motor starts to spin. If the motor starts to turn over wait and let it get spinning and then release the decompression and see if it tries to start. I wait for my oil light to go out and then release it. I set my Throttle at around 2000 rpms. I've used it enough to know were to set it. I've heard it said to set it at full throttle? I Never have. should be able to jump the solenoid and bypass the Ing. Key. I jumped mine at the Solenoid connections. Stater problems 15yrs. ago which finally had to get it rebuilt. 75$ I believe it was.
DECOMPRESSION CABLE ASSEMBLY -