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G1625S
09-01-2010, 06:36 AM
How much noise can one of these things make and not come apart?! I've got a 5 ton military truck. Engine is 855 Cummins naturally aspirated[yuk] Lost a couple pistons bringing it home. #1 and #2. Sleeved them and replaced them also a new head. Other two heads were good. 6 new injectors. Engine had a knock before it came apart. Figure knock was caused by said pistons that melted. Would have done a complete in frame, but didn't have the money. Anyhow, put it all back together and it still knocks. Runs good, does not smoke and has appropriate power. And, I've worked it hard with no signs of failure. So, what could be 'wrong' enough to cause a horrible knocking sound, but not actually have anything let go? Really don't want to pull the pan again....prolly just run it till it pops then look for an old big cam and a 10speed[guitar]

Hvytrkmech
09-02-2010, 07:38 AM
Does it have a compression release, and if it does, is the cable sticking?

1-5-3-6-2-4
09-02-2010, 04:28 PM
maybe there is a rod knocking and it just hasn't let go yet.

G1625S
09-03-2010, 11:28 AM
No compression release. Could be a rod. Gonna save up the money for the rest of the in-frame I started since I see this morning that it's made some oil since I last ran it, so I'm thinking I lost another sleeve. Gonna pull the pan over the next day or so and have a looksee. Thanks for the replies. I'll try and snap a video here in the next few minuts.

G1625S
09-03-2010, 11:56 AM
Ok, crappy video, sorry. You can hear it best when I'm farthest away in the beginning and end:

http://i128.photobucket.com/albums/p191/sloc1443/th_0903101232.jpg (http://s128.photobucket.com/albums/p191/sloc1443/?action=view&current=0903101232.mp4)

DiezelSmoke
09-04-2010, 09:06 AM
If it continues to run probably a loose inj.

Hvytrkmech
09-04-2010, 10:02 AM
If it continues to run probably a loose inj.


I agree, they are well known for breaking injector hold down bolts causing all kinds of noises.

G1625S
09-04-2010, 12:33 PM
Huh, I'll check the torque on those. Thing is, it made the same noise when I bought it. After sleeving the front two, same noise, but all heads got done and all 6 sticks are new and freshly torqued...thanks for the replies:)

DiezelSmoke
09-04-2010, 04:32 PM
They really are a noisy engine as long as you don't have a miss were it shacks the motor keep running it. You may also want to make sure there is no air in the fuel, that will make them knock also, but you don't describe any other problems like slow throttle response, etc.

G1625S
09-04-2010, 05:51 PM
Throttle response is a little sluggish, but then this is my first class 8 engine experience. Can I bleed at the pump return or??? I just bolted it it together and it bled itself in a few cranks. Fires very quickly. Could air still be a problem? thanks again!

DiezelSmoke
09-04-2010, 09:34 PM
Check for air from the return line at the back of the rear head, run the line in a gallon jug and watch for air. You may get air at startup but after you get the jug 1/4 full you should not see any air. I don't think this is your problem you would be complaining about more symptoms.

G1625S
09-05-2010, 04:42 PM
My send and return lines both enter the front head. There are double line connectors that go from head to head to head. I assumed that fuel goes all the way to the back and then returns forward for the return. I'm gonna try and get a better sound clip of the engine. This thing sounds like it's gonna fly apart at any second, but I've pulled the same grade near my house, about 20% in 3rd on the governor several times with no issues. Truck weighs about 35k. Still gonna pull the pan since it made some oil recently. Thanks again for the replies. I'm a little lost here and don't wanna much this big ol engine!

Hvytrkmech
09-06-2010, 07:59 AM
If its making oil, and since you stated you put 6 sticks in it i would be leaning on a faulty injector o-ring. Did you check the thrust washers and the rest of the mains/rods when you had the pan of last time? wrist pin bearings were another problem for those hangers and probably the cause of the noise you are hearing.

G1625S
09-06-2010, 08:06 AM
No, I did not check the rest of the bearings when the pan was down last. No time and not enough money to fix anyway[laugh] Wrist pin bushing makes sense...the knock is not a down deep kind of knock. As for making oil, I think it's coolant, so I'm leaning toward another sleeve gone south:( I kinda got taken on the truck. Was told it was a good runner. Got an hour into the trip home and lost #2 sleeve and piston. Been a nightmare ever since....

Hvytrkmech
09-06-2010, 10:51 AM
What color is the oil?

G1625S
09-06-2010, 03:02 PM
Almost greenish on the stick. Not quite milky, but on its way. I'll post up a pic shortly.

1-5-3-6-2-4
09-06-2010, 11:40 PM
liner oring. sounds like. when you drop the pan, pressure tester on the rad cap, find the coolant tract marks. inside the block.

G1625S
09-07-2010, 06:14 AM
liner oring. sounds like. when you drop the pan, pressure tester on the rad cap, find the coolant tract marks. inside the block.

Can I replace just the o-ring or do I have to replace the liner as well once I press it out?

Had another old school wrench listen to the truck last night and he said they'll run forever sounding that way, so I'm a little more optimistic:cool: Thanks again for all the replies. Gonna try and pull the pan in the nexy couple days.

Hvytrkmech
09-07-2010, 06:20 AM
Yes you can change just the o-rings. the only issue is that when you push the piston out of the liner the rings usually break, so be ready to do more work to it. I use vegetable oil on the o-rings when I set the liners back in.

truckwrench1
09-07-2010, 08:38 PM
just a thought do you have an injector or 2 maybe stuck when tou ran the overhead what sequnce and torque on injectors talking about compression release these are not touch and back off injectors and in my experience plain engine oil works just as good as veg oil also when pan of check end play on crank and deffinently pressure test with pan off. (i also remember cummins revising the overhead set process so make shure u used the correct one)

G1625S
09-27-2010, 03:39 PM
Well, I've had some time to think about this. No time to do anything, just think[laugh] I'm gonna try and shop around for a used big cam as they seem to be pretty reasonable and I could pick up a few much needed HP. It's gonna be faster and darn near cheaper to stab an engine than it would be to tear into this one again. The mil-spec stuff is pretty well limited to the oil pan and coolant purge tank, so any old class 8 engine should pop right in. Thanks for all the advise.