Lukasswaziek

I take the belts off and run it and it seems like it goes away. But alternator is new and I've never heard a water pump clunck or knock like that. Anything is possible I guess🤷

No it is not. That's pretty easy to pick out from everything else

Just bought a "new" truck, an 81 with an e6-350 and I'm starting to use it, I have been hearing an unusual knock in the front of the motor at idle, it sounds almost like two marbles hitting each other, or a hard wood block being hit, and it is inconsistent, or it makes noise at random intervals. Not a constant repeating noise. I first thought it could be a bad harmonic balancer so I replaced it, but no change. Is it possibly a fuel knock? It doesn't seem like it is because I can only hear it right in the front of the engine, possibly the geartrain. I don't want to go too long and destroy an engine, but I also don't need to tear it apart if it's minor. Help would be appreciated

Anyone know the part number for that check valve? E6 leaks down after a couple days. Can't find it online

Been driving lately and it got to the point where it was bad enough to exactly pinpoint it and it's the harmonic balancer. Very loud now. It's Parked and I'm ordering a new one tonight. Also gonna cut the filters on it to look for metal flake.

I kinda wondered if it was a knockoff due to having no markings on it. Still gonna keep it in the collection for a spare!

My girlfriend, who lives in upper Michigan found this bulldog by the shore of lake superior, and as cool as it is, I can't figure out what model or year truck it was on. Anybody have any guesses?

Mechohaulic I have someone here operating the brake while I listen, and when no brake is being applied you can hear it in the cab but it's quiet, when you push on the brake it gets louder until you pass that RPM range. When I listen next to the engine, I can hear what sounds like the same clatter but not as distinct as when sitting in the cab. Believe me this is frustrating. If I could pinpoint it easier it would not be as frustrating. I've worked on trucks my whole working career, and this one is making me really scratch my head

Yes just adjusted the valves, no difference

While it was making that noise and bothering me, I was searching for what It could of been, and there was a small amount of antifreeze leaking from the headgasket that I hadn't noticed before so I suspected that it was a compression leak noise, but it wasn't. No compression passing by the fire rings anywhere. The gasket was weak in a corner though

Okay so got the read ends on jackstands, front wheels blocked. Put it in a higher gear and would drag the brakes and now I'm leaning more twords the engine making the noise. It sounds like a real bad injector knock, but for some reason just resonates in the cab. but then again I'm not hugely familiar with Mack trucks and the noises they make. Mostly worked on and drove cats and cummins. I checked the pto's to see if either one was making the noise and it's not that. If you get it at the right rpm it sounds more like a hard knock rather, but otherwise clatters with the engine firing

Yes truck has 2 pto's

I don't think so. I can't feel a driveline vibration and if it was a tranny issue it sounds like it's at the front of the transmission

So I have an issue that's been going on as long as I've owned this truck, it's a e6 350 with a maxitorque 9 speed. Between 1200 and 1600 rpm I hear a distinct clatter but only under light load and the truck has to be in gear and rolling. When I rev it up in place at that RPM range It won't make the noise at all, and when I'm pulling a heavy load and get into it, it goes away also. Sounds a little too loud to be an injector knock. Oil pressure is around 30 at idle, 60psi at 1600, 90 at 2100 and oil is clean. Just put a headgaskets in it and cylinder walls look great, all still have crosshatching and no scoring. This noise almost sounds like it's coming from the rear of the engine or more like the bellhousing/clutch. Sounds like it's right under the cab when I'm driving. I'm not sure where to start.

Mark T possibly a little compression passing by, but where it is damaged is in a completely different area. Where the headgasket was leaking the liner looked surprisingly fine.