Hey folks looking for a bit more insight into an issue I have.

I have a 00 3.4L V6 Ls with 126K or so on it, bought it with 81K 3 years ago, after the 1st year of owning it and getting the first oil change about a month after purchase (because I wanted to make sure there was fresh good oil in it) I started to notice that I could only average 1700 miles top per oil change before ahving to add oil, and every 4 quarts I'd add would get about the same distance, some oils would run out sooner then others. I checked for all the usual signs of oil loss, burning it and having lots of smoke, don't have, only ever see a little white smoke when its cold out, checked to see if it was leaking from under the engine, not leaking there, and every oil change I check to see if its getting the coolant mixed in, the oil comes out dark brown like any old oil with no white spots or "milking" of the oil.

Then today after taking a freind to work My coolant light came on, stopped at Advanced and got some coolant, popped the radiator cap to add some more coolant and the entire cap area for the radiator has a brown sludge around it and some white grease at teh very center of the cap.

So now my first thought was the water pump but then I remembered it's belt driven and not right off the engine, checked the dip stick since I just changed the oil last month and only have 800 miles, then I figured I'd check about it on google which lead me here and did some searching and found some info regarding my issues but not quiet as definitive of an result as I'm looking for. So I'm hoping someone on here can help me hone in on this issue.

Thanks for any help or insight, and glad to see theres a forum with a lot of monte enthusists, and sorry for the long first post.

 

My first thought would be intake gasket or dummy shaft o-ring but you say there is no oil leak under the hood. I'd still check those areas as they are very prone to leaks of oil and coolant. if the oil comes out brown it could just be the coolant has mixed with the oil from running it that way. Dex-cool coolant doesn't really leave white marks in the oil just the old green stuff did that really.
If the car is burning the oil the catalytic converters are our cars great down fall the get get plugged, clean the oil from the exhaust, and are very sensitive to coolant.
A P0420 code will set if the cat is toast so if it hasn't come on yet it may not be too late.
The brownish sludge under the rad cap is likely just sediment and residue that has been boiled out of the water mixed with the coolant from the factory some years had that problem but its not a big deal just looks bad. In most cases the oil will not end up in the cooling system but coolant is notorious for getting into the engine crankcase. Check the PCV and the oil cap for white froth that is a sign of a bad intake gasket starting to leak.
good luck hope you source your leaks out and fix them.

 

Thanks for the suggestions, the pvc valve looks good and is in good shape it went out last year or rather the tubing on it went out and I replaced it, the engine oil cap is clean, just a light a brown dingey tint on the white plastic. I assume the P0420 code is the O2 sensor or whatever at the cat converter, and I haven't had one of those yet, and I've been thinking about getting that looked at lately since If i rev the engine a little hard I some times get a small puff of white smoke in the cabin and you can smell exhaust.

 

As for the cat, I don't have the specifics, but I think '00-'02 has a recall from GM (you'll have to search on that).

Now you're loosing a large amount of oil. It HAS to go somewhere. The 3100/3400 is known for lower intake gaskets going bad, resulting in oil or coolant lose or both. From my experience with the 3100 (near identical to the 3400), areas to check are:
- Oil Pressure Sensor, look for oil above the starter. If there is, to confirm, disconnect the sensor, use a mirror to look at the connector on the sensor, make sure you and what you are wearing is clear of the belt and fan, have someone start the car (if that is leaking oil there, that's your problem).
- Check around the valley of the lower intake (it's the lowest spot where the intake meets the block. Oily crap is usually there and a good sign the gasket is blown.

Now, you're loosing coolant. See if you can do a loan-a-tool on a radiator pressure tester. Use it to pressurize the coolant system. Listen for hissing and look for signs of coolant seaping out.

Based on what you shared, I don't think the water pump has anything to do with it.

I hope I caught everything (I'm running on very little sleep right now, so if I missed something, I'm sorry).