At work I have been selected to fix our RD688 Mack with a 460. Today began fine, as the day went on there came a slight knock in the motor. By the time we got it back to the shop it sounded like there was a midget in there beating crap with a hammer. Good oil pressure and it did not get hot. I listened around with a probe and it seems to be from the front head in the valve train. I popped off the valve cover and the only thing that I saw off was that on #2 cyl exhaust valve it seems that the spring looks a bit tilted and hitting the side of the head and the washer thing that holds the keepers is also a bit off, but the keepers are still in. SO does anyone have a idea what this could be? Are there any common problems? Thanks for the help.

 

What year is it? Is it a 24 valve?



Tim

 

It is a 1999, 24 valve. Sorry I left that part out.

 

How did the valve bridge look? Mack had some problems with them breaking. It was a common problem.


Tim

 

It all looked fine. I just looked quick but did not see anything broke, were it did not belong. it sounds like valve train noise but seems to be a crank shaft speed, not the 1/4 speed you expect to hear with a vale.

 

Run it with the valve cover off. Messy. I know,but it may help a lot.