I’ve returned with the second installment about engine bearing basics. Today I’m going to discuss what the different markings mean on a bearing as well as the causes of bearing failure. Before we get started, I’d like to remind you if you are interested in learning more about bearings go to our eLearning class. Also, if you have any bearing related questions don’t hesitate to ask…think of me as your engine bearing guru!
The backs of most bearings have numerous markings and there are a range of things that could be on the shell.
Below are just a few examples (See photos for a better understanding):
- Production Date (Month/Year)- Example would be 8-10 or 8/10
- Material Used – Example would be AS
- Shift – Example would be B-11 or A-10
- Part Number – Example would be CB663P
- Position – Example would be Upper or Lower
- Size – Example would be Std. or 0.25mm
Any other stray numbers like 1123221x, etc. are lot and manufacturing codes which are meaningless when it comes to identifying the bearing.
Two things to note: Main bearings will have an MB prefix on the shell, but are mostly sold only in sets with a MS prefix. Go to askmahleclevite.com if you need further help in identifying your bearings.
Finally, many people ask Clevite to identify the size of the bearings, which can be very difficult. The size may or may not be stamped on the bearing and size markings which can be done by color coding isn’t always visible. This is why you should always measure your crankshaft to determine the correct size bearings. Bearing clearance is essential to proper installation and it is much too important to leave size to a guess my friends!
Bearing failures do happen… and often, we look for someone or something to blame for the failure. MAHLE Clevite offers a web-based bearing failure guide with 22 different causes of bearing failures. The guide is complete with digital photos, causes, prevention, and remedial actions. I promise you won’t find anything like it, and the best part is there’s no charge to use it. Why, isn’t that nice of MAHLE Clevite?
To explain failures briefly – 40% of engine bearing failures are caused by dirt and the main sources of dirt are #1 – dirt left in during the overhaul #2 – airborne abrasives and #3 – contaminated lubricants. Myself and the engineers at Clevite can’t stress enough how important it is to clean your crank, rods and pistons before assembly. Scrub oil galleries with a bristle brush, wash parts with hot, soapy water and clean, clean, clean!