That all makes sense, I brought up the PCV valve during the servicing a couple days ago when the overfill condition was discovered and will ask them to check that again when I am there, hopefully today. I don’t have a problem adding oil, just puzzled as to why it happened in the same relativity short timeframe as the transfer case situation. And perhaps the bigger puzzle is what is in the transfer case and how did it get so overfull. Someone would have had to really work to get that much fluid in through the fill hole as it would have been running out the entire time they were filling and I know that wasn’t the case. I can see how it could have come from the transmission, but that fluid level looked fine. Do you think it’s possible for the engine oil to have gotten into the transmission and then some of that fluid in turn into the transfer case? What is the total capacity of the transmission? What’s involved in replacing the seal between transmission and transfer case?
asamaster, you seem very knowledgeable, let me ask you about another issue which I didn’t think was related (but may be?). the engine recently started “losing” coolant. There are no signs of leaks and it seemed to have started after I had the water pump replaced because the pressed housing was leaking. I’m having to add a quart of more every couple of weeks. A thread on the avalanche fan club site talks about castech heads developing a crack. I’m not seeing evidence of coolant in the oil.
“you seem very knowledgeable”…yeah if only my wife and kids felt that way…
Your truck has a “dry” intake manifold so it’s not prone to the intake gasket leak that plagued earlier GM trucks. Early Castech heads had a tendency to leak through porosity in the casting. I’d have a thorough cooling system pressure test done, especially since the coolant loss started after water pump replacement. Coolant loss trumps oil consumption in my opinion. I suppose it’s possible that a qt of coolant in 2 weeks into the oil could be burned off through the pcv system, but I’d still look for an external leak first.
There’s no way your xfer case was 2 qts over full. The capacity is only something like 2.3 qts (I’m not certain, I’m home today). I would drain and fill the case and check the level again in 2 weeks before recommending any further testing or checking. I would change the oil and add ultraviolet dye to the crankcase and check the level and test for leaks with a UV light in 2 weeks.
I stopped by the shop again this morning and talked with another mechanic. We checked the PVC valve and it didn’t look good so I picked one up and put it in. We re-checked the transmission fluid and the level was good and the fluid appeared fine. I plan to go back in a week and we will check the transfer case again and possibly drain/refill. I think we did a pressure test a couple changes back but will ask them to do that as well. What do you think about a UV dye test? Maybe start with the coolant, see if any is ending up in the oil, then test the oil?
A quart every 1500 miles is perfectly within the range of normal oil usage, especially for an engine that size. Do a compression check if you’d like, but the only oil problem I see in the post is the lack of checking it regularly. Youu should not let it get 2 quarts low. As per the fluid, look for some other cause.
Thanks everyone for the input. For those who want to keep telling me to check my oil, please go back and read my posts. I check my fluids regularly and that is why it never got below needing more than a half quart. The 2 quarts was total usage over 3,000m. For those who want to keep telling me that that isn’t bad for a vehicle with that mileage, please go back and read my posts. This is a vehicle that never used any oil before so I was trying to figure out what had changed. As a long time listener to car talk, I honestly thought that I would get some constructive suggestions, not just a bunch of condescending know-it-alls who don’t bother to read the details of the discussion and keep repeating the same advice. ASEmaster and Keith, thanks for your constructive input. Beyond that I am greatly disappointed by this community. If you have something more to say, save it for the next guy, maybe you can help them find the hood release and tell them how to spell oil so they can find the filler cap.
@kinetix … since you seem to have a complaint about the Car Talk Forum service you received here, may I suggest that perhaps you don’t pay your “Car Talk Forum” invoice billing!
Sorry, I just got a little fed up with people who think they are an expert (but obviously know little more than the average joe) and that everyone else is just an idiot that has no idea how or when to even check their oil. Anybody can give that advice and this site certainly doesn’t need everyone chiming in with the same tune. I personally give the general public a lot more credit than that.
kinetix, some of the people that you are critical of here actually do have a good reputation for giving good advice. I almost fell into the trap that some of them fell into, but I had the advantage of the reading your second post before saying anything, and in that post I gathered that you were conscientious about checking the fluids and maintaining your vehicle.
You have done a commendable job in keeping your vehicle for 250k miles without burning any oil. I know it can be done, I’m not really one that is that conscientious about maintenance. My saturn has a little over 250k and it burns about a quart every 1500 miles, but then I only change it about every 6k or so. But it didn’t suddenly start burning oil at that rate, it was a gradual thing. It started at around 100k when it would lose a quart between oil changes, then it was a little more between oil changes. By 200k, it was losing a quart about every 2500 miles.
So your loosing a quart every 1500 miles on a vehicle with 250k on it is not usually something to be concerned with. But the fact that it didn’t burn oil up till now and it suddenly started loosing oil at that rate, that makes it a bit of a concern. Mainly it is a concern because what ever caused the sudden increase in oil consumption could just as suddenly get a lot worse and catch you off guard. For example, if your oil loss was due to a small crack in the oil pressure sending unit, you could top off your oil tonight, the sending unit breaks completely tomorrow and with in a few miles, you dump all your oil.
I hope you find the cause and let us know. I’m am curious, but also feedback, especially if it is something no one thought of is helpful for someone else that comes here with the same problem. Best of luck.
Did you switch to a different brand or weight of oil just before you started losing oil? Some oils don’t seem to “agree” with different engines. Mobil-1 synthetic is an excellent oil, but in my newer car it would use a quart between oil changes. On Valvoline synthetic it would use a slight amount, and with Amsoil (which I have in it now), it uses no perceptible oil between changes.
It could just be your engine is getting worn and you’re getting more blowby and leaks around the valve stem seals. If your catalytic converter is working properly, it will consume the evidence of oil burning at the rate at which you’re losing oil. You might try switching to a full-synthetic oil to see if that helps your usage. (assuming it isn’t leaking somewhere) Also, this time of year with colder weather and longer warm-up times, an engine will tend to use more oil. An older engine needs to be warmed up for all the worn-in parts to fit each other the way they should, and will use a little oil while cold, especially if the vehicle is immediately driven and especially on short trips where the engine is never warmed up fully. Also make sure your PCV valve is working properly and lot allowing pressure to build up in the crankcase.
With Cold Weather And Condensation, Some Cases Of PCV Valves Freezing Temporarily Have Occurred Below 32*F, Even Resulting In Some Manufacturers Designing WaysTo Heat The PCV System.
I literally created a CarTalk account just to post this reply. The exact thing happened to me. And there is likely a commented reply with this answer on this page already. But the answer isssss… Simple? Actually yes this time. I’m nearly certain you will find your actual oil pan still fully loaded. The pan and drain plug for the transfer case on these 5.3 liter avalanches are located much too conveniently so that it is easy to mistake as the oil pan and plug. They also have identical shape and size plugs as well. And to an untrained eye, like the one I had at that time, the dark brown fluid that is gonna flow out that you think is obviously the oil your trying to swap out, is what most ppl call Transmission Fluid. I think you will find this information to be very helpful. and I’m not sure even when you posted this, but ideally you receive this in a timely enough manner to avoid the detrimental aftermath that inevitably haunted me for months following the same mistake I made on this.
If you look in the upper right corner of each post it says when the post occured. The least one on this subject was 12 years ago in Dec 2012…just an FYI