Where to Find the Engine Serial Number (With Examples & Tips)

Common Locations to Find the Serial Number

You’ll often find the engine serial number stamped or on a metal plate attached to the engine block. On many engines this plate is on the left-hand side, near the fuel injection system or oil filter.

Look around the cylinder head or valve cover too. Many manufacturers put the number where it’s visible when the hood is open, often close to injector lines or near the mounting points.

If your engine is heavy-duty diesel, the serial number plate may be in less obvious places: under brackets, on accessory mounts, or near hydraulic components. Carefully clean oily or rusted areas, sometimes light scraping or degreasing is needed to reveal faint numbers.

You might also see it stamped onto the block just below where the head joins the block. That location is common, especially for older engines.

How to Read and Use the Serial Number

Once you locate the engine serial number, the next step is knowing how to interpret and use it properly. This ensures you get the right replacement parts and avoid fitment issues.

First, look for engine type or model codes near the serial number. Many manufacturers place both numbers close together on a flat surface.

Next, break down the serial into segments. Often it includes:

• A prefix identifying engine family or series
• A model number or variant
• A sequence or production number unique to that engine

For example, you might see something like “XJ-4500-12345,” where “XJ” is the family, “4500” is the model, and “12345” is the serial. Use all three when ordering parts, just giving the model may not be specific enough.

When you share the serial with a parts supplier, also mention the engine type and model. That extra detail helps them confirm you get the right engine head, gaskets, injectors, or seals.

If the number is unclear because of wear or corrosion, gently clean the area using a degreaser or soft brush. Avoid scratching or grinding. Then take a clear photo, it helps if the parts supplier wants to verify.

Finally, always record and store the serial number, engine model, and type. Keep a digital and paper record for future services, warranty claims, or rebuilds.

Tips for Heavy-Duty Diesel Engines

Heavy-duty diesel engines often place the serial number in spots tougher to see. Knowing a few brand habits can save you time.

• On Detroit Diesel, you’ll often find the serial stamped on the upper rear corner of the block’s right side.
• On Caterpillar engines, the serial is frequently on a dataplate located on the valve cover or on the fuel pump side of the block.
• For Cummins engines, look on the rocker cover or side of the gear housing. The serial can also be on the engine block itself.
• Check under accessory brackets, near injector lines, or on hydraulic pump mounts. These areas often hide data plates or stamped codes.
• Clean around the suspected area with degreaser or a solvent. Light scrubbing often reveals faint stamps.
• Use angled lighting or a flashlight at low light to see engraved numbers better. Shadows help show depth in faint markings.

With these tips, you’ll reduce the guesswork when dealing with big engines.

How to Verify an Engine Serial Number Before Purchase

When you’re buying a used or spare engine, engine serial number search isn’t just for parts, it’s a tool to verify authenticity and compatibility.

• Ask the seller to take clear, close-up photos of the serial number plate or stamp from multiple angles. That way you can check in your database or parts catalog.
• Compare the engine number, model, and engine type against official manufacturer resources or parts catalogs. If something doesn’t match, that’s a red flag.
• Use the serial number to cross-check build date, version, or configuration (turbo layout, injection type) in factory documentation.
• If the number looks altered, damaged, or inconsistent with the rest of the block, ask for supporting documentation (purchase invoice, repair history).
• When possible, run the engine serial number through manufacturer or third-party lookup tools. Some OEMs and parts suppliers maintain databases for serial verification.

This extra step protects you from buying a mismatched engine, getting wrong replacement parts, or losing trust with customers.

Quick Takeaways

• Engine serial numbers tell you the exact model, type, and production info you need.
• Many numbers are stamped on the engine block or head, often near injectors or valve covers.
• On heavy-duty diesel engines, the serial may be under brackets, near mounts, or in hard-to-see spots.
• For used or purchased engines, always check the serial number. Ask for photos, compare them with catalogs, and look for matching documents.
• Clean the surface gently, use angled light, photograph the number, and record model + type along with the serial.

Conclusion

Knowing where to find an engine serial number is important. Adding the step to verify it before buying gives you confidence, reduces risk, and prevents errors when ordering parts. By checking carefully, cleaning, documenting, and matching it to catalog or supplier data, you protect your business and your customers. Use these tips every time you inspect, repair, or purchase an engine.