!966 Oil Consumption Issue

[Stevison]

Folks, I need the advice of you technical savvy Caddy drivers out there because I am at my wits end! I have is 66 Fleetwood El Dorado,429 motor, just turned 60,000 miles original, runs like a champ, but I'm losing a quart of oil every 100 to 150 miles. I have a minor seep/leak after it sits for several days, but that certainly wouldn't account for the volume of oil will going through the car. Knowing that the car had sat for a while, I had new valve seals installed and I also had a compression check run. The compression on seven of the cylinders was right at 165 pounds, the eighth was 150 pounds, but because it was within 10% of the others, my mechanic did not think that that was the source of the problem. When you mash it, you can see the black smoke out of the exhaust. I've heard a variety of theories, including but not limited to, a bad PCV valve. Obviously it's sucking oil from someplace. I really hate to get the engine remanufactured when it runs so well. If you all have any will will will ideas I will be most grateful! Thanks much,Stevison

["Cadillac Kid" Greg Surfas 15364]

1 quart every 100 miles is of course quite excessive.  It points to a lot of engine wear "someplace".  Perhaps the valve guides are worn and the "new" seals are, for some reason defective.  The compression pressure sounds okay, but at this point I would expect cylinder wear might also be a major contributor to your one person attempt at emptying the Saudi Arabian oil fields.
Greg Surfas

[scotth3886]

could it be really a badly leaking rear main?

[walt chomosh #23510]

Put a quart of Lucas heavy duty oil stabilizer in,....and please report the results....walt...tulsa,ok

[Jeff Rosansky CLC #28373]

If it sat for a while then rings are likely frozen. Take the pcv off and plug it at the carb. Then start it and see what comes out of the engine side of the pcv. Our 55 was that way. It sat for years. It just has a big environmentally friendly vent tube. When we first started it it blew so much oil smoke out of the tube I thought I had a broken exhaust. I ran it a few hundred miles with Marvel's in the oil and the rings unfrroze and the smoke stopped...... Now it just leaks 🙂.
So I would suggest running it reasonably hard with Marvel's and see if it fixes itself.
Good luck.

Jeff R

[V63]

A few suggestions.
I would verify the correct capacity is met, and the dip stick reads correct. Smell the oil for gasoline. A failing fuel pump can dilute the oil with gasoline. The 'smoke' you report is black and it should be 'whitish blue' if oil consumption. This could be a RICH fuel mixture washing the cylinders of oil. What viscosity oil are you using? You could up the viscosity and add Lucas as suggested above for a viscosity issue or marvel as also suggested depending on desired result. Check your plugs for oil consumption moreover do a proctology test and swipe the tail pipe for oil deposits.
Take a valve covers off and verify the heads are 'draining' Oil back into the block, if the engine has had  sludge and it's now breaking free, it can greatly restrict those drains.

[tmdeturck]

What do the plugs look like?

If it's burning that much oil, I would expect a blue cloud to be following you everywhere.  I think that's a greater oil to gas ratio than my old 2 cycle weed whacker uses!

[E Masters]

For the leak pour in a bottle of stop leak. It will freshen up seals and gaskets a little.

[fishnjim]

For a non-catalytic year, the accepted visual for oil consumption via combustion is blue smoke, not black.
Black is indicative of rich mixture, sooting or carbonizing the fuel from lack of oxygen.  So that's another issue, fuel mixture too rich.   It may "run good" but is far from operating well.
That oil leak equates to 1/4 oz per mile, so is not a "big" leak, per se, like a hole makes.   Has minor drip accumulation leaking, as noted, so it can be "spraying" oil during operation, so I'd be looking at the underside for oil film also.   A loose valve cover or other gasket leak, seal, etc. can easily do this.   A valve cover leak usually will usually end up on the exhaust and cause smoking in the engine compartment.   
Blow by from the rings will force the engine oil mist up through the PCV and into the carb but it's supposed to stop pressure and evacuate the gases.   So a PCV change is easy but may not solve your car's issue.   

[Ralph Messina CLC 4937]

Stevison,

Fishinjim provided you with  some good advice that I'd like to add to. My last '66 had been used very little over 10 years. It had major leaks at the gaskets and  was covered with dirty greasy deposits; but did not smoke. . The compression was in the 170's. Because of the filth in the engine compartment, I decided a complete cleaning and all new gasket were in order. Once out of the car I noticed the top of the engine and underside of the hood had a heavy film of oil......no indication of a leak, more like it was sprayed on. I found that the PCV tube from the valley cover to the carb base was almost completely clogged. The engine reciprocating action creates pressure in the crankcase  that had no release other than up the oil filler tube. Considering a crank speed of 1- 2000 rpm, there's a lot of mist generated that could easily amount to the ¼ oz per mile noted above.

Is This a California spec car with a 3/4" tube connecting the carb breather to the top of the driver side valve cover? There may other dynamics involving the AIR pump

Absent any blue smoke exhaust, I strongly suspect the oil is being expelled through the breathing system rather than burned during combustion.

HTH,

[Stevison]

Gentlemen, I so greatly appreciate your prompt and thorough responses. I'm going to check for the mechanical issues discussed, if no luck try a can of marvel, and if no luck, I'll ship it out to S&J Engines for a re- manufacture! Thanks again and I will keep everyone posted as to what works/doesn't work.

[scotth3886]

Given that I'm also a 66 owner with an engine that his never been opened up, I'm wondering if you ever figured out what the issue is.  I've done just about everything else at least once.  Last issue was rear main.  Due to all of this work, I was changing oil much more often than normal intervals.

This summer I was finally able to let it go for a normal change interval before I do my fall change for winter.

What would be considered normal consumption for a 66 429.  I've run 2,500 miles on this change and I noticed that I'm down almost a quart.  Is that anything to be concerned with?   I haven't done valve stem seals yet.  I figured that would be next. 

[wrefakis]

2500 miles on a quart on a 429 that is beyond great leave alone