How to check a flywheel?

Jan 23, 2014
Hi guys,

I am about to purchase a second hand flywheel (single mass).

Just wondering what I should be looking out for? Is it like brake rotors where there should be a minimum thickness?
the surface, for gouges from running a disc too long. crazing, which is fissures/small cracks. < a machine shop may be able to mill small flaws off.
checking is hard/dark spots & can be milled/sanded off back to decent metal. And teeth, don't want a chipped tooth or shaved down teeth from many years use.
Some flywheels, like VW air cooled also feature the surface the main seal rides on. Another inspection surface.
A big piece of glass can show warping, otherwise it's pretty much all visual-cracks, deep grooves, burn marks, etc. I pray for the DMF in my F-450 every time I use it!
Visual inspection, mic it up for thickness and compare it to OE thickness. How many times it was cut? IMO I'd probably pass and buy new. Replacing a clutch and flywheel is no longer a fun job for me.
I'll never forget back in my younger days, I did a clutch job on a van I owned. I just thru a new disc and pressure plate on it and bolted it back to gether. When I started it, the clutch would start to grab a 1/2 inch off the floor, with no adjustment to it. When it heated up, that 1/2 inch went to about 1/4 inch. I took it all back apart, and had the flywheel cut. Night and day difference. I swore to myself I would never go all thru that again if I had to do a clutch on anything. Live and learn.,,,
If it has grooves and or small “bluish” colored heat crack you need a new one. Also check for a “ware ring” on the back where the rear main seal is. .