Weird engine

[matuva]

Good day all,

we're having a strange engine :

this engine was just rebuilt. We put brand new main & rod bearings and piston rings. Known good heads...

Once in the truck, the engine did start easely. Good oil pressure, beyond half the gauge and close the 3rd of gauge reading. Then, after few minutes running, we saw the oil pressure gauge needle wiggling, oil pressure suddenly drop down to the 1st 1/4 of the gauge. Immediately we heard the noise of the engine changing and a strange "wook wook wook ..." appeared, like if a valve stuck opened (just a bet) and the engine started running rough with emission of a lot of white smoke smelling unburnt fuel.

Just in case, we swap to another IP. No luck.

This is especially critical when cold, where the truck smokes a lot. It goes a little better once hot, but still smokes. Oil pressure is now study at 1/4 of the gauge, doesn't move a lot from iddle to rev.

If we disconnect the IAT sensor, things immediately go better, and if you too disconnect coolant temp sensor (the one on the T-stat housing), of course iddle revs up to 1 000 rpms, but smoke almost disappear, just a haze stays.
With those 2 sensors disconnected, truck respond almost well on test road, other than the white smoke coming back when under load.

No codes, and the IP is set at -0.70

I'm a bit at lost

 

[WarWagon]

Dropped a pushrod with a broken nylon retainer? Timing needs to be advanced? TDCO learn done?

 

[matuva]

Timing is within OEM specs

Yes, TDCO and time set were performed, timing set at -0.70

Is oil pressure high enough?

 

[ak diesel driver]

Put a mechanical test guage on it and see what the oil pressure is with that. If oil pressure is low then something has changed, spun a bearing, dropped push rod etc. did you pre lube the engine when you first started it?

 

[matuva]

Yes, we use Permatex red stuff (assembly lubricant), and we primed the oil pump before starting.

At start up, the engine rattles, during 1~2 second, just time for the oil pressure to build... It seems something is wrong in mains maybe?

I'm a bit afraid we get a damage somewhere, especially because all happened after this sudden drop in oil pressure...

 

[6.2 turbo]

Oil pressure regulator probably stuck. Happened to me several times.

 

[ak diesel driver]

Too much assy lube can be bad as it will plug passages before it gets warm enough to be pushed thru.

 

[matuva]

Oil pressure regulator probably stuck. Happened to me several times.

Where is it? inside oil pump?

 

[Twisted Steel Performance]

There are 2 pressure valves where the oil filter screws on, 1 is under a 1" metal plug, the other is beside it, they should have been replaced during the rebuild with new ones. You might have one or both plugged up..

Check with a manual gauge and see, if the pressure is really that low, something is wrong..

 

[Missy Good Wench]

The valves spoken of are the filter bypass and the cooler bypass.

The pressure regulator valve is in the cover of the oil pump.

The wook wook noise is likely from (as mentioned) a push rod issue, rocker came off due to a broken rocker button.

The low oil pressure is not likely related to those items though.

The next course of action is to figure out what caused the sudden drop in oil pressure.

Does the oil pressure stay low, or will it come up again when the engine is cold ???????

Is this a late block with oil squirt nozzles ???????

A missing Squirt nozzle will cause a huge loss of oil pressure.

There are 8 of these in the engine.

The are inserted up from the main line through the extra passage in the block.

Some times these can fall out during block cleaning.


IMHO THE ENGINE NEEDS TO COME OUT AND APART
Something is causing the loss of pressure and must be located


Good luck and keep us posted

Missy

 

[Burning oil]

Got a video of it? maybe someone will reconize the sound.

 

[3500GMC]

Somebody needs to re-visit their work.