Knock in new engine(with sound file)

[83Blzr62]

I have started getting used to the sound of my new engine and have noticed an obvious knock. It comes from the rear passenger side of the engine. After researching I have narrowed it down to an injector or lifter. If it idles for a while or I just started it the knock can't be heard, but after coming down from a high rpm it is obvious. I cannot pin point it with the stethescope and I have loosened the #8 and # 2 injector lines and it seems to get louder while loosening the #8 line. I reused the cam, pushrods, and injection pump, but have new lifters, rocker arms, and injectors. The heads were shaved and the block was decked but my pistons were shaved also. Any ideas or have you heard this sound before?
Thanks,
Kyle

[john8662]

I can't hear it in that clip, it's short and the quality isn't there.

If you need a place to send a larger mainly un-compressed file, try www.sendspace.com you can upload up to 100mb there. and post the link here.

Try a longer clip with just the engine idling, say for 30 seconds of good time, that way I can hear the knock. Or a longer clip with the engine running at idle, then rev it up to 2k, hold it for 10 seconds or so, then back to idle for a little while.

What things did you check during assembly?

Did you get the opportunity to check how far out of the deck the pistons were at TDC? When you're dealing with topped pistons, shaved blocks, it's a very good idea to know where you're at.

The spec is .006" out of the hole, some build it more, which puts the piston and valves closer to one another.

I sure hope this is something simple!

What brand lifters did you use? Out of curiousity.

[83Blzr62]

I checked bearing clearence on the rods and mains, crankshaft endplay, piston ring end gap, and where the piston was at tdc. It is lower compression so the pistons were .010 to .015 under the deck height. The lifters were from the diesel depot and they said that they were what they used in every engine that they built so I went ahead and used them. I used my digital camera so that is why the quality is so low. I will use a better video camera and take a longer clip following your guidlines. I should be up tonight.

[C.K. Piquup]

Sounds more like a "tap" than a "knock" to me.I`d take a stab and lean towards a lifter.See what others think.A bad lifter won`t sound any different on a diesel or a gas motor,injected or carbed.

[Slim shady]

If you have an injector that is open just losening the injector will not make the noise go away. You need to swap injectors or replace the injector you think is bad and see if the noise moves form one cylinder to the other or goes away.

Swap #8 if that is the one from the right side to the left front and then see if the noise moves. An open or partially open injector will sound exactly like a valve hitting a piston.

I should know I bought new injectors and they ran fine for an hour then #8 failed and the motor developed a knock like a valve was hitting the piston. Removed the head to make sure and found no damage,reassembled everything then eventually replaced the injector after talking with my brother in law who is a Mercedes Diesel mechanic.

Slim

[83Blzr62]

The lifters are fine and not springy at all. I ran it with the valave covers off and they all also pump oil. I will swap the #6 and #8 injectors with the #1 and #3 and see if that works. My pushrods are slightly shorter on some so I will find the longest pushrods I have and put them in.

[john8662]

My pushrods are slightly shorter on some so I will find the longest pushrods I have and put them in.

All the pushrods should be the same length.

I usually check them by sanding them all up on a flat surface and looking with the naked eye. If I can't see the difference, then it's likely not a problem.

But if you can visually see the difference, then perhaps that is your problem.

Not too hard to remove all the pushrods for a look-see, since you have the valve cover off...

J

[83Blzr62]

Yeah, I measured all the pushrods and they are only slightly different. I changed them around and it did nothing. I know all the lifters are solid so they are not the problems. I changed the number 8 injector with the number 1 injector and there was no difference. I could not get to the number 6 injector because the exhaust manifold was in the way. Next I will check comnpression and if it is higher on cylinder 8 maybe a valve is hitting it slightly. I hope it is the # 6 injector though. I finally got my parents video camera, so I will try to get a better sound file up. Didn't arveetech have a similar problem? I cannot find any of his posts, did he ever get it resolved?

Thanks,
Kyle

[arveetek]

Didn't arveetech have a similar problem? I cannot find any of his posts, did he ever get it resolved?

Thanks,
Kyle

I didn't really have as much of a "knock" as it is a "tap." :D But to answer your question, no, I haven't resolved the issue. I did finally figure out that the sound I'm hearing is coming from the gear drive. Basically, the gears are loading up and and unloading, due to uneven pulses at idle. I suspect a problem in the fuel delivery system. It runs great, though, so I haven't done anything yet in almost two years to find a cure.

I only notice a problem at idle. At higher rpm, she smoothes out and runs like a scalded ape!!

It looks your engine is nearly a carbon copy of mine. I do wish now that I had spent some more money and purchased the injectors from Kennedy. The ones I got from Accurate Diesel I feel are very cheaply done. He doesn't do the rebuilds himself, they're from somebody else that he bought them from. So you know the quality can't be the best. I'm not for certain how good his injection pump rebuild is, either, but it seems to be okay.

On another note, I'm having trouble searching posts older than 1 year. I've been in contact with Jim and Greg about it.

Casey

[83Blzr62]

Mine is a tap also, but can be heard above idle. I can't get the video off the video camera on to my computer so I can't get a better clip. I know it has to be fuel or compression related, so i will work from there.

Thanks for the reply

[john8662]

A couple more things to consider (for the both of you).

Exhaust leaks sound like ticking!

Since both engines in this scenario are turbocharged, you have a crossover pipe.

Using the springs and nuts off a typical exhaust pipe won't work well for a crossover pipe (for a reason).

There is a reason why GM used Bolts on the crossover pipe on the 6.5TD's, this is to properly seal the flange to the donut.

The typical exhaust fastener is a stud in the manifold and springs and locking nuts. They won't hold and will leak. I'd suggest fixing this one of two ways.

Make spacers out of pipe or washers and use the nuts to compress on the flange (no spring). Replace the studs with Bolts of the appropriate thread pitch and length (probably metric if I'm guessing).

Gear drives, yeah they can make noise in these engines. I have finally come to the conclusion that this can be due to:

1) excessive align bore
2) no camshaft endplay

My '86 6.2 engine falls under the first problem. I base this on the fact that when I stall the idler gears that they are very tight and don't have much rocking play, and any slight rotation of the engine will place the gears in mesh where you can't pull them out. Too tight!

On another engine recently assembled it was way looser than I had gotten used to on the 6.2 block of mine. It makes NO noise, except heard with the oil filler cap off. It needs to be loose.

I think DSG offers custom gears, I may try again soon when I pull my timing cover off yet again to install a reluctor wheel to convert the engine over to DS4.

J