855 question
09-01-2010, 06:36 AM
#1
Registered User
Thread Starter
855 question
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
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
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
09-03-2010, 11:28 AM
#4
Registered User
Thread Starter
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.
09-04-2010, 10:02 AM
#7
Administrator ........ DTR's puttin fires out and workin on big trucks admin
Trending Topics
09-04-2010, 12:33 PM
#8
Registered User
Thread Starter
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
09-04-2010, 04:32 PM
#9
Registered User
Join Date: Mar 2008
Location: Madison, Wisconsin
Posts: 201
Likes: 0
Received 0 Likes
on
0 Posts
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.
09-04-2010, 05:51 PM
#10
Registered User
Thread Starter
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!
09-04-2010, 09:34 PM
#11
Registered User
Join Date: Mar 2008
Location: Madison, Wisconsin
Posts: 201
Likes: 0
Received 0 Likes
on
0 Posts
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.
09-05-2010, 04:42 PM
#12
Registered User
Thread Starter
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!
09-06-2010, 07:59 AM
#13
Administrator ........ DTR's puttin fires out and workin on big trucks admin
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.
09-06-2010, 08:06 AM
#14
Registered User
Thread Starter
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
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....
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....