How did this happen to this camshaft?

[PierreR]

Was looking throug old pic,s in my computer and found these that i took at work a few years ago.
This camshaft is in a MAN TGA engine and when we were going to adjust the valves on it the cam looked like this on almost all of the camlobes.



At that time the truck had 620000km,s on it.

 

[Highline9]

Looks like an air pocket in casting, made on a fri or mon. A bad part made it to a good engine or lobe cast to small for that grind.

 

[ZeeOSix]

Looks like major wear on the start of the lobe ramp. Was this wear only on the side of the lobe that hit the lifter first as the cam rotates? If so, then it could be a problem with the case hardening of the metal, and this wear is from the initial impact of the lobe with the lifter as the cam rotated. Could also be related to the cam lobe profile being too aggressive at the start of the lobe ramp, thereby causing high impact force every time the cam started opening the valve. Lack of oiling, and inferior oil use may also be a factor ... could be many factors adding up in the wrong direction.

620,000km (385,000 miles) might have something to do with it also, depending on how this engine was taken care of and driven for that long.

 

[PierreR]

The wear was only on one side of the cam and it was the side that hits the roller on the valvelifter first.

Could be inferior oil, because this started to happen on their trucks after they decided to change the oil by them self.
That company has 10trucks that this has happend to that i know of, they own over 200 so it could be the same problem on more.

 

[TiredTrucker]

The Cummins ISX engines had this problem. A TSB from Cummins said it was a bad production quantity. I had to replace a camshaft and rockers on my ISX at 750,000 miles, which was about the time most were loosing them. Seems like a lot of miles unless you are familiar with commercial truck diesels. Cams should easily go well beyond 1 million, and still be good. I have taken a few class 8 truck engines to beyond 1 million miles without ever having to open the engine up for more than the top end adjustment.

 

[Merkava_4]

A collapsed lifter will do that.