Model: YC4108
Part Number: D30-1004001
Brands: Yuchai
Engine Model: YC4108
Engine Type: Diesel
Scope of application: light and medium trucks, agricultural machinery, generator sets, marine auxiliary
Yuchai built the YC4108 over many years with several piston specifications. Part D30-1004001 is one of those numbers, distinct from A8600-1004001 and B8800-1004001, and the correct choice depends on the engine's production period and compression ratio rather than on the bore size alone.
This is a common source of trouble in the field. A piston that fits perfectly can still be the wrong part, and the error only shows up as smoke, hard starting or poor economy once the engine is running. Comparing the old crown with the new one before assembly avoids the whole problem.
A diesel piston takes combustion pressure at the crown and passes it to the connecting rod, while conducting heat into the rings and liner. In a YC4108 working on a farm or a construction site, that cycle repeats for hours at a time with little cool-down, so the cooling path through the ring pack matters more than any short-term behaviour.
The bowl shape controls how the fuel charge mixes with air, the ring grooves control sealing, and the pin bore controls noise. Each of these is fixed at manufacture and cannot be adjusted later, which is why the correct part number matters.
Every piston is measured at the points that decide durability rather than only at the diameter. The checks are quick but they separate a piston that lasts from one that smokes within a season.
Every failed piston carries evidence of its cause, and reading that evidence before ordering parts is what prevents a repeat failure a few months later. A melted crown edge points to over-fuelling or late injection, a cracked crown centre to overheating, and scuffing on one side to a bent rod or a misaligned bore.
Assembly is straightforward if the measurements are made first. The most common mistake is fitting a piston and rings without checking end gaps in the actual bore, which produces blow-by that looks like a machining fault later.
Two pistons with the same bore can differ in compression height and bowl shape, and both will physically fit. The wrong one changes the compression ratio and the combustion pattern, producing smoke and high exhaust temperature that no injector adjustment can correct.
Agricultural engines work in conditions that punish filtration. Dust reaching the cylinder acts as an abrasive between rings and bore, and it also contaminates the oil. Check the air filter housing seals and the intake hoses whenever the engine is serviced, not only when performance drops.
New pistons and rings need load to seat. Vary engine speed, apply moderate load and change oil and filter early. Holding a constant heavy load glazes the bores, and a gentle break-in that never loads the engine is equally harmful because the rings never bed in.
Correct injection timing, clean fuel and adequate cooling keep pistons alive. Replace fuel filters at interval and fix overheating promptly, because a piston that has been hot is permanently weakened even if it still runs.
Keep the piston in its packaging until the liner is clean and ready. Store it upright rather than stacked on its crown, and keep the pin and circlips with the piston they belong to. A dropped piston can be distorted without showing any visible mark, and the resulting noise is hard to trace after the engine is assembled.
Compare the old piston crown and the engine plate, or send us photos.
It is supplied bare by default. Complete assemblies are available.
Yes, if the liner and the rest of the set are undamaged.
Over-fuelling, incorrect timing or blocked cooling.
Browse the Yuchai piston and components category, and pair the piston with the YC4108 piston A8600-1004001 or the YC4108 piston ring D30-1004016.
Yuchai YC4108 Piston (1004001). Heat and pressure both arrive at this component first. The ring grooves control oil and compression, and the bowl decides how efficiently the fuel burns.
Check the ring groove width with the old ring and a feeler gauge. An opened groove lets the new ring flutter, and a fluttering ring breaks.
Numbers beginning 1004 are numeric-series numbers used on later WP7 and WP8 production, where mounting detail changed without a change of nominal type. On this engine, confirm the YC4108 application against the engine plate before ordering.
Check piston-to-bore clearance and ring end gaps in the actual bore. Measuring in a spare liner gives a false reading and is a common cause of oil use after a rebuild.
Ordering note. Photographs of the actual unit can be sent before dispatch on request. That is the cheapest way to avoid a return when a casting revision is in doubt.
Related reading: Piston Ring Selection: Gap, Tension and Bore Condition
| We Are 30 Years Diesel Engine Parts Supplier | |
| Brand | EPID |
| Warranty | 12 Months |
| Condition | 100%New |
| More Models | Weichai: YC4108, and other Weichai series. |
| Shipping | By sea / air / express (DHL, FEDEX, TNT, UPS, EMS) |
| Packing | Standard exporting packing or as required |
| Payment Term | L/C, T/T, Western Union, Trade Assurance |
| Delivery Time | 3-7 days (depend on order) |
| Selling Point | 1. On-time Delivery 2. Genuine Quality Assurance 3. Professional Supplier |
Every piston is measured at the points that decide durability rather than only at the diameter. The checks are quick but they separate a piston that lasts from one that smokes within a season.
Every failed piston carries evidence of its cause, and reading that evidence before ordering parts is what prevents a repeat failure a few months later. A melted crown edge points to over-fuelling or late injection, a cracked crown centre to overheating, and scuffing on one side to a bent rod or a misaligned bore.
Assembly is straightforward if the measurements are made first. The most common mistake is fitting a piston and rings without checking end gaps in the actual bore, which produces blow-by that looks like a machining fault later.
Two pistons with the same bore can differ in compression height and bowl shape, and both will physically fit. The wrong one changes the compression ratio and the combustion pattern, producing smoke and high exhaust temperature that no injector adjustment can correct.
Agricultural engines work in conditions that punish filtration. Dust reaching the cylinder acts as an abrasive between rings and bore, and it also contaminates the oil. Check the air filter housing seals and the intake hoses whenever the engine is serviced, not only when performance drops.
New pistons and rings need load to seat. Vary engine speed, apply moderate load and change oil and filter early. Holding a constant heavy load glazes the bores, and a gentle break-in that never loads the engine is equally harmful because the rings never bed in.
Correct injection timing, clean fuel and adequate cooling keep pistons alive. Replace fuel filters at interval and fix overheating promptly, because a piston that has been hot is permanently weakened even if it still runs.
Keep the piston in its packaging until the liner is clean and ready. Store it upright rather than stacked on its crown, and keep the pin and circlips with the piston they belong to. A dropped piston can be distorted without showing any visible mark, and the resulting noise is hard to trace after the engine is assembled.
Browse the Yuchai piston and components category, and pair the piston with the YC4108 piston A8600-1004001 or the YC4108 piston ring D30-1004016.
Compare the old piston crown and the engine plate, or send us photos.
It is supplied bare by default. Complete assemblies are available.
Yes, if the liner and the rest of the set are undamaged.
Over-fuelling, incorrect timing or blocked cooling.
EPID supplies diesel engine parts for Weichai, Baudouin, Yuchai, Caterpillar, Sinotruk, FAW Xichai and Cummins engines. Every order is checked against the original part number before packing, and our team can identify a part from a photo of the engine plate. Ask for a quotation with your model and quantity and we will reply within one working day.
