1995 Bobcat 743B Engine Knock

[Tazza]

Yeah, that noise is not the engine, that is something loose rattling around. That engine sounds sweet as

 

[ZekeSkyree]

I also agree that it does not sound internal. Something is loose and perhaps an exhaust leak, which can sound like a knock. You need to find someone in your area to look at it. I love the idea of going to a rental place to find someone .... Never thought of that before.

 

[foton]

united rentals here provide a customer owned equipment repair service, I think it is done on a reginal basis so one one rental shop in a area will do this,so just cause it is a united might not mean they will provide this service,but can give you a location of one that does. For my wacker nueson I used them before we got a dealer close by to use.

 

[haymaker]

I've been watching this thread, and as an old gas engine mechanic I can't help but wonder... What do you deisel guys think about this?
1st, Since it does start and run well, check & eliminate the possibility you have a valve that's out of adjustment. Valve lash gets looser as the engine warms up, it seems weird that it doesn't knock at startup, and I have - very rarely - seen an adjustment come loose.
2nd, if it is the bottom end, the biggest thing is to stop using it before rolling a bearing scoring the crank beyond hope. Pull the engine, drop the oil pan, and inspect the bearings ad journals. With 6k hours they will be worn. More importantly, how does the crankshaft look? If it looks okay, measure it with a micrometer to verify the size, that it hasn't been machined before.
If still good, roll in a new set of main & rod bearings and reassemble with new gaskets.
Is this the best route? Obviously not. But if the engine is in otherwise good shape, it's an economical way to squeeze a few more years out of it while you save for the inevitable rebuild / replacement. I've seen this done.

I have done this with gas tractors several times with good success. Especially mid season when I didn't want to take the machine down for any length of time.
Sometimes you get lucky.

 

[how900]

It difficult on a video clip as the noise we hear on the clip isn't always what is happening in real life...but if it was me.....I would get a cheap mechanics stethoscope from Harbor Freight or amazon and start by trying to work out if it is the top or bottom of engine, then if it is the top i would pull the rocker cover off and check the valve rocker clearance and springs are ok. didnt really sound like bottom end to me which i expect to be more of a dull knock, but as I said it not easy on a video.

 

[1702]

Where are you located in Ct ? I'm here also. It doesn't sound bad to me these engines do kinda have that sound and I can also here the lose clamp or something. But I don't hear a rod bearing that's for sure. Maybe a main bearing but I don't think so either.