Where do you find the serial number for a 5 quart glas bowl for the Artisan mixer

You can try running the mixer at high speed for a few minutes to try to blend the grease in the gearcase. If this does not work, then cleaning out the old grease and repacking with new is the solution.
Assuming you have a 4.5 quart tilt head, a 5 quart lift bowl (not the professional series), or an Artisan, the Service Manual you need is at:

http://www.kitchenaidparts.eu/documents/pdf/service-manual/classic-svc-manual-new-email-version.pdf

smell the motor housing for any burnt smell.suggest you buy a new one.theire not worth fixing

Google Kitchen Aid in your home country.

Any number of reasons such as:
Bad electric cord
Bad brush or brushes
Bad armature or stator
Control plate broken

You need the Service Manual:
http://www.kitchenaidparts.eu/documents/pdf/service-manual/classic-svc-manual-new-email-version.pdf

While this manual does not cover the Artisan specifically, the procedures do apply.

The model number seems to be valid-but given the age of the unit few parts are readily available. You might want to try eBay or a used appliance store (or even Goodwill) to find a donor machine.

You can find the User's Manual (which shows how to adjust beater-bowl clearance) for your model at:

https://www.kitchenaid.com/customer-service/manuals/

The KSM5 and the KSM150 are different mixers. They are both 5 quart mixers and use the same gearing and motor. However the bowl design is different. The KSM5 is a 5 quart bowl lift, which means the bowl locks into the arms of the mixer and raises towards the head of the mixer, where the ksm150 mixer is a artisan mixer, which is also a 5quart mixer, but the head of the mixer tilts back and the bowl twists into the base ring to lock into place. These two mixers will take different bowls and beaters.
Thank you,
Colleen
Customer Service
MendingShed.com

If the base is not holding the bowl properly then only a replacement base plate or another bowl is going to fix it. The base plate is held onto the pedestal with 3 Philips head screws.

You should be able to find a manual here:

http://shared.whirlpoolcorp.com/product_literature/search.jsp?siteCd=KA_EN_CA

Note that your model number seems to be incomplete; I found 63 manuals for this model number; there should be 3 more characters in the model number.

This may have a simple solution: This sounds like an issue of beater to bowl adjustment, which can come out of alignment naturally over time and with use of the machine.

If the flat beater is striking the bottom of your bowl, this may cause the locking mechanism to loosen and may cause the mixing head to "bounce" during use.

Your Use and Care Guide will cover the "beater to bowl adjustment," which you can do at home in a few minutes with a flathead screwdriver.