rod knocking

[ron55]

I am not sure!
After oil change I let it set for a few days without starting and when I started it up ,working on vaccum line to the HAV, I happen to crawl under the front and I could hear a rod knocking sightly, could not hear it inside.
Had my wife run the throttle up and down and the knock went up and down with the rpm. I have heard rods knock before and buy the time you hear them going down the road it is bad.
Shut it off and restarted after a bit and no knock.
anybody experience a knock after a oil change?
I would think if it is a rod, it shouldn't have stoped knocking on the restart

[Photog]

What you are hearing might be "piston slap". It goes away as the engine warms up.

[iRV4FUN]

Agree, "piston slap".

Did you pre-fill your filter?

[oemtech]

Remember, GM and Workhorse say it's NORMAL.

[justimagination]

After oil change I let it set for a few days without starting

............Possibly lost your prime in the oil pump, as mentioned in op, always pre-fill oil filter which primes oil pump much faster. Good luck and travel safe.
David G.

[bdpreece]

Could be a lifter. At this point it is a scary proposition. Buy some engine flush and follow the directions. then install new oil and check for noise.

[ron55]

I always prefill the filter and I know the different sound between a lifter and a rod. I am about sure it was a rod bearing it was low in the oil pan I would think the piston slap would be high and you should be able to hear it in the cab, anyway I am going to have my wife start it again while I am underneath, if no knock I going to Colorago and if it knocks I am going to try to pull the oil pan. I should be able to change the rod bearings from below?
Really, my big question, are these engines that built that loose, that a rod bearing would knock without enough oil and then be ok once it got enough oil?
All rod bearing that I have had knocking, I could find excess movement by hand after lowering the oil pan.

[DriVer]

There is a big difference between piston slap and a rod knock. The piston slap will definitely go away a rod knock typically will not once it starts.

Piston slap will sound very repetitious perhaps like marbles in a can but a rod knock will be a singularity and can be almost timed.

I do experience piston slap when the engine has sat idle for a few days perhaps but the sound always goes away. GM says it is normal however there is a lot written about it if you Google it. My attention always peaks when I hear any knocking however my concern lessens in time and as the engine's temperature increases. I have found that it hardly matters what kind of oil you use and I would not recommend that anyone go with oil greater than 30W.

From the Workhorse Shop Manual:

Installation Procedure
1. Install the oil filter to the engine block. Tighten
the oil filter per the oil filter manufacturer’s
instruction printed on the oil filter box.

That's it!

[oemtech]

Piston slap is not normal on PROPERLY built and assembled engine. Mine does not have the problem so why should any of the others.

Same goes for oil consumption. A quart to a tank of gas is BS and when you GM/Workhorse say this will be normal for 36,000 miles. It kind of makes you wonder when the Engine Warranty length is the same as their claim.

If you Google GM Piston Slap and GM Oil Consumption you will have enough reading material to last at least a week.

[DriVer]

Quote:

Originally Posted by oemtech Same goes for oil consumption. A quart to a tank of gas is BS and when you GM/Workhorse say this will be normal for 36,000 miles. It kind of makes you wonder when the Engine Warranty length is the same as their claim..

Dale, I'm sorry but that is not in evidence anywhere here on this board. What they told us is that a 1Qt oil consumption per 100 gallons can be considered normal however what we all see here in fact is that we can normally extend that interval out by 85% to 100% but these engine will consume oil.

Your own personal experience may differ. I may consume a quart of oil in ~1,250 miles. Doing the math on that shows that for me it works out to about 2.5 tankfulls or about 187 gallons per quart of oil. This does not upset me. We have seen where folks don't use any oil between changes so if that's the case that brings in a question if perhaps that engine is too tight or is mine or others too loose. Regardless it has little to do with Workhorse.

[Mekanic]

Is it really that difficult to remove the oil pan on yours? If caught early (and it sounds like you may very well have done that) you could pull the pan and inspect the bearing and replace any bad ones.
Quite easy once the pan is off.

[dieselclacker]

ron 55,

You mentioned that the noise went away after running and then re starting after sitting for awhile. A rod bearing would knock probably more so after warming the engine, while a mild piston slap will go away due to the expansion of the piston within the cylinder as the engine warms. I would think you are hearing one or more poor fitting pistons in your engine rather than a rod bearing. You can hear a lot more noises while laying under a running engine that you can standing over one. Aluminum pistons expand really fast while standing idle in an warm engine that isn't running and has no oil or coolant circulating.

Dieselclacker

[ron55]

I have no more knocking after two or three days of staring so I am going to do nothing unless I hear more. thanks everbody

[DriVer]

Quote:

Originally Posted by ron55 I have no more knocking after two or three days of staring so I am going to do nothing unless I hear more. thanks everybody

Ron, Excellent! Keep your ear to the rail ....