What to look for when buying a 318
Note: Where it says pictures there will eventually be pictures/video of the topic.
What to look for when purchasing a 318:
Hours: Number of hours may or may not be a great place to start with a machine. Onan engines that are taken care of will last many thousands of hours, in fact it is not unheard of to get 3,000 plus hours without a rebuild. However, most Onan’s need fresh rings (at the least) somewhere between 1,250-1,750 hours. Freshening the rings is covered in the repair section. An indication of ring wear is engine compression (covered in the compression section below). Also keep in mind while the hydraulic pumps and the differentials on 318 would be classified as overbuilt, pay attention to the total machine hours. Also make sure the hour meter is working. In most cases, 318’s generally have between 700-1,500 hours on them when they are for sale in the market today. This obviously will increase as the tractors get older.
Year: Use the serial number chart to establish the year of the 318, then you can use it to establish what engine (B43G or P218) the tractor should have. In some cases older tractors, 1983-1987 may have P218G’s for replacement engines. Figuring out the year may also assist with parts etc in the future.
Leaks: Check for leaks. The most leak prone areas are the oil filter adapter, the main PTO end engine seal, and the power steering cylinder.
Oil Filter Adapter:
Oil will leak out of the filter adapter and catch and the flywheel where it is spun up into the air cleaner resulting in this mess.
PICTURES
http://www.mytractorforum.com/showthread.php?t=260999
Other threads related to the oil filter adapter leaking
http://www.mytractorforum.com/showthread.php?t=262526
http://www.mytractorforum.com/showthread.php?t=191592
http://www.mytractorforum.com/showthread.php?t=136953
A leak in the front seal is easily distinguished by the oil caked onto the front of the engine. The power steering cylinder is not serviceable so if it leaks it will need to be replaced or rebuilt at a shop with the proper equipment. Pay attention to the lines running to the steering cylinder to ensure they are not cracked or worn. There is a tendency of the lines to wear on the cylinder itself, which over time may cause failure.
Deck: The 300 series came with either a 38 inch (rare), 46 inch, or 50 inch decks. There is also a more modern 48 replacement deck that can be distinguished by the turn-able wheels.
PICTURES
Of these decks, the 50 inch deck is the most desirable because of the hi lift ability and cut quality. The 46 inch deck, commonly called the 48 because of its actual dimensions, is the most numerous and while the cut quality is not on the level of the 50 inch deck , the 46 inch deck does a nice job mowing. The replacement 48 inch deck has similar cut quality to the original 46 inch deck.
Steering: There should not be any play in the steering. Two bolts located on the axle can be adjusted to reduce play in the steering. In general you should be able to turn the wheels with one finger.
Cracks: There are some reports the frames of these tractors can develop cracks around the transmission and the steering cylinder. These cracks can be repaired with the proper tools.
http://www.mytractorforum.com/showthread.php?t=244186
Maintenance: Is there any maintenance history, as stated in the “hours” section maintenance is important on these Onan’s any documented maintenance history is a plus but it should not be a deal breaker. Maintenance history can be inferred by the condition of the tractor itself.
Compression: If you can test the compression it is highly recommended. Cylinder compression should not change between a hot and cold engine and should not be more that 10 lbs different between the left and right cylinders. Good compression is between 90-105 and excellent compression is between 105 and 115. From the factory these engine should have a compression of 110-120.
Air filter: Onan’s need clean air. Dirty air filters may indicate premature engine wear.
How clean is the engine: Onan’s are air cooled engines. Air must be funneled around the engine to keep it cool. Dirty cooling fins will cause the engine to run hot, contributing to premature wear. With the engine at WOT you should be able to feel the air from the engine at least 5 or more feet away from the front of the tractor.
PICTURES clean vs not clean
Oil pan mounting tabs: If an engine has been removed and not properly re-installed the two front oil pan tabs have a tendency to crack and break off. This is not a difficult or expensive fix. However, it may indicate the engine has been removed for some type of maintenance or repair.
Oil itself: The oil should not be gooey or gritty. It should be clean
Start Up and Running: All the safety systems should be hooked up. Any modification in the safety systems (seat, neutral, and brake depending on the year) could indicate other short cuts were taken. A small amount of black smoke at start up is normal, other than that there should be no smoke from the engine. The engine should run without any choke. The starter should engage smoothly and quickly. There is a starter improvement kit that is sold or can be made for 318’s. However, hesitancy of the starter my indicate other issues within the starter or improper grounds in the electrical system.
It is normal for a 318 to require a couple of seconds worth of cranking to start if it has been setting for a decent amount of time. The pulse fuel pump, powered by the crankcase must prime the fuel lines.
The engine should idle smoothly (950 RPM) and response to increases in throttle without hesitation. WOT for Onan’s is listed at 3600, however, John Deere recommends 3,450 for WOT. At WOT with no load the engine should be smooth and not “hunt”
The PTO should engage quickly and smoothly and the engine should respond similarly. Typically there is a brief puff of black smoke when the PTO is engaged. Once the PTO is on the deck should sound like a fan and not rattle or vibrate. Rattles and vibration are a potential sign of bad bearings and worn out pulleys. Additionally the deck shell should be in good shape and not thin from mowing in dirt/sand. The deck should also be level and when mowing not scalp the grass or mow unevenly.
The tractor should remain in one place with or without the parking brake on when the hydrostatic lever is in neutral. Any “creep” can be adjusted. There should be a limited amount of whine from the hydrostatic pump when the tractor is in motion.
Drive it around and put it through its paces!
Note: Where it says pictures there will eventually be pictures/video of the topic.
What to look for when purchasing a 318:
Hours: Number of hours may or may not be a great place to start with a machine. Onan engines that are taken care of will last many thousands of hours, in fact it is not unheard of to get 3,000 plus hours without a rebuild. However, most Onan’s need fresh rings (at the least) somewhere between 1,250-1,750 hours. Freshening the rings is covered in the repair section. An indication of ring wear is engine compression (covered in the compression section below). Also keep in mind while the hydraulic pumps and the differentials on 318 would be classified as overbuilt, pay attention to the total machine hours. Also make sure the hour meter is working. In most cases, 318’s generally have between 700-1,500 hours on them when they are for sale in the market today. This obviously will increase as the tractors get older.
Year: Use the serial number chart to establish the year of the 318, then you can use it to establish what engine (B43G or P218) the tractor should have. In some cases older tractors, 1983-1987 may have P218G’s for replacement engines. Figuring out the year may also assist with parts etc in the future.
Leaks: Check for leaks. The most leak prone areas are the oil filter adapter, the main PTO end engine seal, and the power steering cylinder.
Oil Filter Adapter:
Oil will leak out of the filter adapter and catch and the flywheel where it is spun up into the air cleaner resulting in this mess.
PICTURES
http://www.mytractorforum.com/showthread.php?t=260999
Other threads related to the oil filter adapter leaking
http://www.mytractorforum.com/showthread.php?t=262526
http://www.mytractorforum.com/showthread.php?t=191592
http://www.mytractorforum.com/showthread.php?t=136953
A leak in the front seal is easily distinguished by the oil caked onto the front of the engine. The power steering cylinder is not serviceable so if it leaks it will need to be replaced or rebuilt at a shop with the proper equipment. Pay attention to the lines running to the steering cylinder to ensure they are not cracked or worn. There is a tendency of the lines to wear on the cylinder itself, which over time may cause failure.
Deck: The 300 series came with either a 38 inch (rare), 46 inch, or 50 inch decks. There is also a more modern 48 replacement deck that can be distinguished by the turn-able wheels.
PICTURES
Of these decks, the 50 inch deck is the most desirable because of the hi lift ability and cut quality. The 46 inch deck, commonly called the 48 because of its actual dimensions, is the most numerous and while the cut quality is not on the level of the 50 inch deck , the 46 inch deck does a nice job mowing. The replacement 48 inch deck has similar cut quality to the original 46 inch deck.
Steering: There should not be any play in the steering. Two bolts located on the axle can be adjusted to reduce play in the steering. In general you should be able to turn the wheels with one finger.
Cracks: There are some reports the frames of these tractors can develop cracks around the transmission and the steering cylinder. These cracks can be repaired with the proper tools.
http://www.mytractorforum.com/showthread.php?t=244186
Maintenance: Is there any maintenance history, as stated in the “hours” section maintenance is important on these Onan’s any documented maintenance history is a plus but it should not be a deal breaker. Maintenance history can be inferred by the condition of the tractor itself.
Compression: If you can test the compression it is highly recommended. Cylinder compression should not change between a hot and cold engine and should not be more that 10 lbs different between the left and right cylinders. Good compression is between 90-105 and excellent compression is between 105 and 115. From the factory these engine should have a compression of 110-120.
Air filter: Onan’s need clean air. Dirty air filters may indicate premature engine wear.
How clean is the engine: Onan’s are air cooled engines. Air must be funneled around the engine to keep it cool. Dirty cooling fins will cause the engine to run hot, contributing to premature wear. With the engine at WOT you should be able to feel the air from the engine at least 5 or more feet away from the front of the tractor.
PICTURES clean vs not clean
Oil pan mounting tabs: If an engine has been removed and not properly re-installed the two front oil pan tabs have a tendency to crack and break off. This is not a difficult or expensive fix. However, it may indicate the engine has been removed for some type of maintenance or repair.
Oil itself: The oil should not be gooey or gritty. It should be clean
Start Up and Running: All the safety systems should be hooked up. Any modification in the safety systems (seat, neutral, and brake depending on the year) could indicate other short cuts were taken. A small amount of black smoke at start up is normal, other than that there should be no smoke from the engine. The engine should run without any choke. The starter should engage smoothly and quickly. There is a starter improvement kit that is sold or can be made for 318’s. However, hesitancy of the starter my indicate other issues within the starter or improper grounds in the electrical system.
It is normal for a 318 to require a couple of seconds worth of cranking to start if it has been setting for a decent amount of time. The pulse fuel pump, powered by the crankcase must prime the fuel lines.
The engine should idle smoothly (950 RPM) and response to increases in throttle without hesitation. WOT for Onan’s is listed at 3600, however, John Deere recommends 3,450 for WOT. At WOT with no load the engine should be smooth and not “hunt”
The PTO should engage quickly and smoothly and the engine should respond similarly. Typically there is a brief puff of black smoke when the PTO is engaged. Once the PTO is on the deck should sound like a fan and not rattle or vibrate. Rattles and vibration are a potential sign of bad bearings and worn out pulleys. Additionally the deck shell should be in good shape and not thin from mowing in dirt/sand. The deck should also be level and when mowing not scalp the grass or mow unevenly.
The tractor should remain in one place with or without the parking brake on when the hydrostatic lever is in neutral. Any “creep” can be adjusted. There should be a limited amount of whine from the hydrostatic pump when the tractor is in motion.
Drive it around and put it through its paces!