Buying Guide
How to Read an OEM Part Number Before You Order
The number on the old part is the most reliable thing in the whole transaction. Reading it properly removes most of the risk from a cooling parts order.
Every reference published here is catalogued against the OEM numbers it replaces, and most listings carry more than one. That is not padding. A part that served three model years often carries a superseded number, a current number and sometimes a number from a second brand in the same group.
Supersession Chains
Manufacturers replace a reference when the part changes, but the old number stays in circulation on vehicles, invoices and workshop systems for years. When a listing shows several numbers, they are usually a supersession chain. Quoting any number in the chain will find the part; quoting none of them will not.
Group Numbers and Shared Platforms
Platforms shared inside a manufacturer group carry references from more than one brand. That is why Thermostat Assembly for Volkswagen and Audi lists Volkswagen and Audi numbers together, and why Thermostat Assembly for Citroen and Peugeot covers both marques. A number that looks foreign to the badge on the car is often correct.
Formatting Traps
- Spaces are not significant —a Mercedes-Benz number written 211 501 08 82 is the same reference as 2115010882.
- Trailing letters are significant —a suffix letter usually marks a revision, and dropping it can change the part.
- A leading letter can be part of the number —references beginning with A on Mercedes-Benz parts are common.
- Zero and the letter O —read them off the part rather than from a handwritten note.
Internal References
Alongside the OEM numbers, most listings carry an internal reference such as the one shown on Coolant Water Flange Pipe for BMW OEM 11118511205. It is stable across model-year changes and is the easiest number to reorder against once the first order has been placed.
What to Send With an Enquiry
The number off the part
Photograph it rather than transcribing it where you can.
The vehicle details
Make, model, engine and year settle most ambiguous splits.
A photograph of both ends
Connector geometry separates references that share an outline.
The quantity
It changes the price and the packing, so it belongs in the first email.
The complete published cross-reference list downloads as a CSV from the downloads page.
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References Discussed Here
Answers
How to Read an OEM Part Number Before You Order —Questions
Does an OEM number mean the part is original equipment
No. The number identifies which original part the replacement interchanges with. It is an identification reference, not a claim of original equipment supply.
What if my number is not in your list
Send it anyway. The published set is a subset of a range that runs to more than 4000 types.
Which number should I use when reordering
The internal reference where one is published. It does not change when the OEM number supersedes.
Can you identify a part from a photograph alone
Sometimes, but not reliably. A photograph plus the vehicle details plus any legible number is a much safer basis than a photograph alone.
Do you cover more than one brand per platform
Yes, where the platform is shared. Group references are listed together on the same product page.
Have a Reference You Cannot Place
Email the number with the vehicle details and you get an answer rather than a catalogue link.