Engine sludge

[Caddyholic]

I am resealing the engine of my 62 CDV with 56k miles. I removed the oil pan and there was 3/8 inch of grey sludge in the bottom of the pan it was like clay. There was some in the valley pan also. I had no idea what it is. I ask my dad about it and he said he use to see this in cars that ran shell oil back in the day. The engine otherwise was clean . Have any of you ran in to this or have an explanation to this?

[The Tassie Devil(le)]

This sludge is an indication that the car was a Grocery getter and a Sunday to church driver.

The sludge is caused by the engine hardly ever getting to normal operation temperature, and thereby not burning off the condensation that accumulates with internal areas.

An engine needs to be driven at least 50 miles before it starts to normalise itself in the expansion and contraction department, and it needs to get really hot inside to "de-contaminate" the oil.

As an example, my '37 Chev with a warmed up L88 BBC engine wouldn't eliminate piston slap until I had driven 50 miles, and I couldn't really push it hard until it was warm enough.   This engine had 12.5 to 1 Forged Pistons, (with a skirt clearance of .008") Aluminium Heads and Soild Lifter Camshaft.   Yes, this was an extreme road car, but it shows that temperature is required, no matter how tight, or loose tolerances are.   But, this was a 600 HP engine.

Bruce.

[Caddyholic]

But what is this substance? Most sludge I have seen is black or milky (that indicates moisture). It was like medium gray clay that was not runny. I could not cut it with engine degreaser or simple green. I used paint thinner to get the last residue off.

[bpowell]

I was always told that the grey hard sludge you are talking about was lead from the leaded gasolines that were in use.

I haven't seen it in engines exclusively using unleaded fuels.

Bpowell

[Caddyholic]

Bingo that makes sense. So now I have 8 fl oz of a controlled/banned substance.

[Walter Youshock]

Also remember that these cars had ventilated oil caps and dowdraft tubes exposing the internals to the atmosphere.  Unless it was converted to pvc, you're sucking humid air through the engine.

I seem to remember being told an d trick was to drain the oil and pour kerosene down the oil filler to clean out the pan.  I wouldn't do it but...

[cadillacmike68]

You can always distill it and make fishing line weights out of it!

[TJ Hopland]

Be careful, that sludge may be all that is holding your oil pan together.    Almost every pan I have encountered that had a lot of sludge in it had a bunch of pin hole leaks after I cleaned it out.   Guessing moisture gets trapped at the bottom and rusts the pan from the inside.  That sludge does a fine job of sealing things. 

[The Tassie Devil(le)]

Also does a fine job of covering things up.

I have an non-Cadillac, but a GM car, just below the Cadillac, and the previous owner pulled the engine down because of the slightest of a rattle, and found that one piston had lost half of its' skirt.   

The previous owner was a mechanic, and said that he couldn't find any of the missing skirt in the sump, but as we were chasing parts, didn't bother to clean up the parts till the replacement parts arrived.   Sadly, I ended up buying the car before he passed away, and proceeded to rebuild the engine.

Putting the sump in the parts washer revealed all the missing skirt pieces, totally embedded in the 1/2" deep layer of sludge.   Don't know how long ago the piston had broken, but the sludge did a good job of hiding the many pieces that the skirt became whilst being hit by the crankshaft.

Bruce.

[Caddyholic]

The pan has no rust at all. And I did not find any gold coins in this sludge.