250 Engine Rod Knocking??

[swbradley1]

So I finally get a M818 and picked it up from GL.

She starts right up but was blowing white smoke that smelled like anti-freeze. Andrew at GL WPAFB is a mechanic and he said that it is a relatively easy fix. Find the offending cylinder and pull the head.

The other problem is that it sounds to me like it has a rod knocking. It has been a while since I have heard one (about 40 years now) so I'm not sure.

I had the truck towed home and started it up with a jump and backed her into the barn.

So any ideas on what to do or where to start? It is a 2002 rebuild and the engine looks like a new or rebuilt Cummins. Should I scrap it or change the engine or rebuild the one in there?

Thanks for any suggestions.

steve

 

[Warthog]

Sometimes a bad/sticky injector will make the knocking noise. If the truck has been sitting for awhile (don't all GL trucks?) I would put some DieselClean in the system and run it to see if it clears up.

Since the head gasket may be leaking keep an eye on the temps.

 

[swbradley1]

Never thought of an injector making that loud of a knock. I'd like to fix the truck but I don't want to remove one or all three heads and fix everything on top and then end up with a rod problem and have to pull it all apart again.

If I pull the heads I plan on pulling all the injectors and having them cleaned and tested.

It's been a long time since I have done engine work and then only on gas engines, nothing the size of this thing.


thanks
steve

 

[gimpyrobb]

Its a 250, they all sound like they knock!

 

[swbradley1]

Well next time you are in my 'hood I will start and you can listen to it. I will have beer. steve

 

[mistaken1]

My old votec instructor was fond of saying "rods don't knock very long".

 

[Stretch44875]

Just drop the pan and see if the rods have any play in them. It will be obvious which one is knocking. Took me about 2 hours to drop the pan on the mulitfuel and have it back up.

 

[swbradley1]

Have it back up as in just the pan or fixing a problem?

When I pull the heads I will do all of them because I want to do it right so I'm guessing dropping the pan won't hurt.

steve

 

[seanm]

I think you were there doing the recovery the same time as I was looking around. You had it towed home on a wrecker? I was sitting on the tailgate of a white crew-cab in front of the office when you left.

Looked like a nice one.

 

[nk14zp]

Are you sure it's a rod knock and not a fuel knock?

 

[supermechanic]

Pull the valve covers.
One by one, cut out cylinders by bearing down on the injector rocker, (hammer handle works well for this).
The noisy rod will be evident when you cut out that cylinder.

 

[swbradley1]

And that is why I posted to the site. While I trust what Stretch tells me I prefer to not drop the pan if I don't have to. It sounds like taking the injector out of the equation is similar to pulling a plug wire on a gas engine, at least conceptually.


thx
steve

 

[nk14zp]

Yes same idea after you find the knocking cyl try moving the injector to a different cyl to see if the knock moves.

 

[nk14zp]

And a fuel knock will smoke white.

 

[swbradley1]

Well it is smoking white. I figured it was all just anti-freeze. It looked like a smoke screen on Omaha Beach during D-Day. I like the truck even with its warts right now.

thx
steve