1st Oil Analysis on Rebuild

[jerry598]

Had an oil analysis done this week. Changed the oil the first time at 300 miles, then again at 2100 miles. So, with 1800 miles on the oil, the oil analysis shows 2 abnormal readings, one for lead at 45, and one for silicon at 53.

The report for the lead level of 45 indicates some bearing wear and the silicon level indicates a possible leak in the air intake. I might also have contaminated the sample by bumping the open container on the underside of the frame, but, what about the bearing wear?

Is this lead level and the associated bearing wear normal on a rebuilt engine? Or, were my bearing clearances possibly too tight? If it's normal I assume the lead level should decline in subsequent samples. Anybody have any experience with this?

My neighbor, who is a heavy diesel mechanic, told me the results from the first oil analysis would scare me.

Should I be scared?

[DmaxMaverick]

Not scary. Often, it takes 3 or 4 (or more) normal interval changes to get it all cleaned up after an overhaul. Your numbers are quite low, compared to what they could be under the same situation.

Check it after 10K to 20K miles. Until then, it wouldn't be "abnormal" to double-dip the oil filters (2 filter changes per oil change, about midway).

[rustyk]

I agree. The silicon is a bit high, but only relatively - actually, it's quite low for a rebuild. Lead on a rebuild is normal - it's the main constituent of babbit bearings, and they will take some early polishing by running. If the copper and tin were abnormally high, maybe a cause for concern, but all appears to be normal.

Watch the next half-dozen analyses...things will moderate.

Actually, I'm a recovering Fuels and Lube Engineer. What I learned from years of taking and submitting samples is that unless one is running lube to the edge of breakdown analysis is a waste. Change the oil every 3-4K miles, and pocket the analysis costs.

[Robyn]

Here is a little tidbit that far too many do not factor into the numbers.

When starting a new engine, the whole system needs to be primed up to full oil pressure so that the complete engine, filter, cooler and lines are all full of oil.

With this done the initial startup wear factor is reduced significantly.

If the engine is started with just the prelube on the bearings it can take 10 to 15 seconds possibly longer to fully fill the entire oiling system and get it up to pressure.

Cranking the engine for a period to fully prime the fuel system also adds to the wear and tear.


The results of this are going to show up in the oil analysis.

My personal procedure is as follows.
While the engine is still on the stand, using an old vacuum pump oil pump drive (Modified) I run the oil pump (cooler lines jumpered at the block ports) to get full oil pressure and oil flow to all the rockers (15 minutes usually)

Once the engine is in the truck I run the pump again to fill the oil cooler and the lines.

Now I spin the engine with the glow plugs out to get fuel to the injectors.

At this point I install the glow plugs and then start the engine.

Initial wear on the cylinder walls from the rings will add to the mixture.
Even under the best possible conditions there will be some dirt. dust and other debris left behind too.

As was mentioned, run the thing and get another couple oil changes on it.

If after two more change intervals, you are still seeing abnormal numbers, then you may need to worry.

Bearing brand and construction can vary a lot between the different products available for these engines.

No matter how careful you are on a rebuild there is still going to be some initial wear on the startup.

The outer surface layer of the bearings is very delicate and any dry spots, even for a few seconds will "Burnish" the top layer of the bearing material and cause it to shed some materials.

Hope this puts your mind at ease.

Missy

[bobt]

Hi, Robyn or anyone else with an answer. Robyn's oiling procedure is comprehensive and likely prevents excessive wear. I'm now curious. What do the manufacturers do upon initial start-up of their new OEM engines? Anything like what Robyn does, or do they just let her rip?
Bob

[Robyn]

I dont know for absolute sure but, suspect that the oiling systems are prefilled using some connection point during the vehicle assembly.

As the vehicles reach the end of the assembly line they are started and driven off.

This is not a big undertaking so everything must be ready to go.

The engines are spun via outside power ???? after assembly is complete.

Jim (More Power) has been through the factory and may be able to add something here.

The things that we as mechanics have to work with are far less sophisticated so we just have to get creative. :)


Check out this video http://www.youtube.com/watch?v=WPxr2DvWUsM
It may shed a little light on how automated this stuff is at the factory level.

Missy

[MPrichard]

I'm just getting round to putting the new heads on a fresh rebuild that's taken the better part of 2 years to finally get to this stage converting my '93 Sub k2500 to diesel from the 7.4l with 452k miles. I don't have a modified vacuum pump drive as you describe, but before scrounging around junk yards to find one, I thought it might be easier to get a drill powered external pump and run it in the oil cooler loop. While this might not fully prime the pump itself, it should get everything else, I would think. It occurred to me that one might not be able to "suck" oil through the non-moving pump, but I could just as easily pull the oil from the dipstick tube, perhaps, albeit at a lower flow rate. I've looked and looked but haven't seen any references to this approach to priming which makes me suspect it's not a great idea, but thought I'd run it by the experts.

[JohnC]

You cannot suck oil through the pump. Pre-lube kits often connect up to the sump drain.

[Kennedy]

The drill/drive system is the simplest solution for the DIY user.

My engine shop uses a preluber to actually install the oil in my Dmax builds rather than try to move it from the sump. My guess is that this is how AMG and most OE's do it as well.

[Robyn]

Scrounge up an old vacuum pump and either grind the teeth off the gear or turn them off in a lathe.

Remove the top part and tack weld a Nut onto the shaft to drive the thing.

There is a tiny oil hole in the anulas groove on the stem of the unit.

This supplies oil to the pump drives bearings. Peen or otherwise seal this hole shut.

Clean it well and a little dab or JB weld.

If you dont, oil comes out the top of the unit and makes a mess.

For the short time that this "Tool is used" the bearings will live forever with the minimal use they get.


You can't suck the oil though the engines gear pump.

Also you can't just drive the oil pump without modified pump drive in place as the oil will not get to the engine, it just dumps back into the pan from the oil galley thats exposed when the pump drive unit is out.

Missy