94 6.5 rod knocking but not?

[Landon730]

My dad has a 94 6.5 in a 2500 and its been run for about 2000 miles now and ever since we swapped the motor, its sounded like it rod knocked. Has good oil pressure, lots of power, no signs of anythings wrong, and the noise doesn't get worse. We took the passenger side head off and found out a nut had fallen into the motor while being installed. Pryed it out of the top of the piston and put it back together. Noise is still there. Truck is currently parked after blowing oil cooler lines. I'm going to change them tonight and try to start it. (Been parked since May). I know theres no issues with the bearings. Could it be the cam?

 

[ak diesel driver]

try loosening the injectors one at a time while idling. Injectors will sound like a rod knock when sticking

 

[Landon730]

try loosening the injectors one at a time while idling. Injectors will sound like a rod knock when sticking

I know what sound your talking about had a different motor that did it. I’ll try the injectors but it should have got primed by now as many miles that have been put on it. I’ll let you know if that changes anything. Do you think it could be a actual injector? Motor was out of a humvee and had water get into it. ATF works magic for that by the way

 

[MrMarty51]

When cracking injector lines, that removes compression from each individual cylinder. If the knock quits, then that could be a bad injector on that cylinder or it could be the cylinder that has the knocking rod. Verify that it is not the injector before condemning the rod bearings.
If the knock gets louder and the injectors are known to be good, then it could be a piston, cracked or slapping.

 

[Will L.]

When cracking injector lines, that removes compression from each individual cylinder. If the knock quits, then that could be a bad injector on that cylinder or it could be the cylinder that has the knocking rod. Verify that it is not the injector before condemning the rod bearings.
If the knock gets louder and the injectors are known to be good, then it could be a piston, cracked or slapping.

Right idea except it does not remove compression from that cylinder. It removed the fuel from that cylinder.

So if you lossen injector nuts one cylinder at a time, you can id which cylinder is knocking.
Then by swaping that injector with one from another cylinder, if it follows the injector, you know it is just an injector. If it stays at that location, you can then test for the cause

 

[Landon730]

Right idea except it does not remove compression from that cylinder. It removed the fuel from that cylinder.

So if you lossen injector nuts one cylinder at a time, you can id which cylinder is knocking.
Then by swaping that injector with one from another cylinder, if it follows the injector, you know it is just an injector. If it stays at that location, you can then test for the cause

Ok sounds great I don’t think it’s nothing internal besides maybe cam, lifters or injectors greatly appreciate y’alls help

 

[Will L.]

Just understand it’s important to follow diagnostic processes or it gets crazy expensive fast. Ive seen lots of folks want to just tear in cuz they get an idea. Next thing ya know it’s a load of parts being thrown at it usually followed up with a for sale sign.

 

[Landon730]

Just understand it’s important to follow diagnostic processes or it gets crazy expensive fast. Ive seen lots of folks want to just tear in cuz they get an idea. Next thing ya know it’s a load of parts being thrown at it usually followed up with a for sale sign.

Ok I nearly did that with my black 94 lol. Ill try injector lines first like y'all had said and then the moving injector if lines make no difference. Still gotta change oil cooler lines first though

 

[WarWagon]

My dad has a 94 6.5 in a 2500 and its been run for about 2000 miles now and ever since we swapped the motor, its sounded like it rod knocked. Has good oil pressure, lots of power, no signs of anythings wrong, and the noise doesn't get worse. We took the passenger side head off and found out a nut had fallen into the motor while being installed. Pryed it out of the top of the piston and put it back together. Noise is still there. Truck is currently parked after blowing oil cooler lines. I'm going to change them tonight and try to start it. (Been parked since May). I know theres no issues with the bearings. Could it be the cam?

Where have I heard of this before? I just can't place it. I do fuzzily recall having to put NOS slugs in an engine over one eating a worm clamp and different heads as several valves hit pistons and were bent as the clamp parts bounced around in the intake. Did you have both heads off? Did you check ALL pushrods for being bent? Did any pistons show valve impacts like this? (linky)

So yeah be careful with loose injector nuts as high pressure diesel can puncture your hand and resulting damage can take the entire hand, arm, and a minor side effect can be death. Shut off engine then loosen injector nut...

With blowing an oil line if the injector test doesn't show anything frankly, run it till it dies. IMO You simply don't have long from the damage done when the oil line blew. If you have a lot of other knocks now the hand writing is on the wall of short life before complete failure. A False hope is change the oil after warm up to get the rest of the no-oil derbis out of the engine and filter. Was the oil line under warranty or did you learn the hard way why we change them as part of the $1000 in other stuff required when swapping an engine?

Warranty = the oil line supplier just bought you an engine and/or rebuild.

 

[Twisted Steel Performance]

We took the passenger side head off and found out a nut had fallen into the motor while being installed. Pryed it out of the top of the piston and put it back together.

This leads to a squished bearing at the least by the sounds of it....

 

[Will L.]

Yeah, I didn’t mention but I think you’ll find major lower end damage by the description. But still eliminating a single injector is worth it. Deciding money to invest vs run till it pukes is a serious conversation to have.
Did you check the harmonic balancer btw?

 

[Landon730]

Yeah, I didn’t mention but I think you’ll find major lower end damage by the description. But still eliminating a single injector is worth it. Deciding money to invest vs run till it pukes is a serious conversation to have.
Did you check the harmonic balancer btw?

Not since engine was put in Marchish 2018. This is this trucks 3rd motor. Truck has 201,000 miles. Harmonic balancer is same one as the last motor. First motor blew oil cooler lines and spun main bearings. 2nd motor was WORN.. OUT.. had to be plugged in over night and glow plugs heated 3 times to start on a 90 degree day. It basically has no rings at this point. It would be a good rebuilder though. Now this one which is a VERY late model 6.2 (set up exactly like a 6.5 block but its a 6.2). I changed the oil cooler line which was a used line. It blew right past the metal. (I thought it rubbed a hole cause they were touching) and got it started it the noise is so. hard. to explain. The motor runs peeeerfect. Has great power. Strongly thinking the cam because my dad told me he had changed a chewed up lifter a month or so before the oil cooler line blew. At this point he just wants to run it till it dies. The drivers side head has never been off. This motor has about 4000 miles on it. Came out of a humvee.

Dont know how to tag people but this is to WarWagons post.
I believe my dad over slick 50 now lol. Motor was run about a mile after oil pressure dropped to the red. Motor sounds BETTER then I remember honestly which just confused me. Cares 40 psi warm. The head that was taken off actually had a messed up valve so we changed the head. The side that hasn't been taken off seems like has the noise. My dad (I kind of agree at this point) wants to just run it till it dies. It sounds exactly like a good running new 6.5 just with a little tik. Ill try to get yall a video of it as soon as I can to help yall out