pkess3

Hi, I just picked up a 2004 Grand Cherokee Overland with 136k miles. I had to downgrade from my 2008 Jeep Wrangler Unlimited Rubicon that was lifted on 35's. I plan on eventually lifting this stock WJ and getting to be similarly capable as the JK eventually. I have other concerns right now though because as I was taking her out on a good drive today up into the mountains around Vegas, she started to have some blue smoke blow out of the tail pipe. I'm not talking just a few puffs but enough to engulf the vehicle behind you. Just before this, the check engine light also came on. I checked the oil level and it was fine. The engine is also running fine. No apparent loss of power (at least for what I'm used to). The blue smoke has been intermittent. Sometimes blows really bad. I drove down the mountain for 10 miles after seeing the first puffs and checked the oil again. It was at the "low" marker so I added almost a quart of oil until it read in the safe zone again and then proceeded to the nearest auto parts store to find out what the check engine light code was reading. It turned up two codes of which both said the oxygen sensors were reading wrong air mixtures. This might be due to all the smoke from oil getting into the combustion chamber and burning (hence the blue smoke) but I'm not sure. All I know is that what looked and ran like the perfect WJ has now got some possible major issues. My brother is a young mechanic and he says it could be bad piston rings or valve cover seals. There's also a humming sound when reaching speeds of 65mph on the freeway. I think this might be due to driveline vibrations or issues. There appears to be a lot of fluid leakage around the differentials and transfer case.

I'm just throwing this out there to see if anyone with a similar vehicle has experienced these kinds of mechanical failures/issues and has an idea to what might be causing these. The only other jeeps I have owned are my JK unlimited and a Patriot of which both were purchased new and never had any of these type of mechanic issues. Any insight or comments are appreciated! Thanks and glad to be a part of the forum!

-Preston

Bustedback

It could be worn piston rings or valve guide seals. Replace the PCV valve and see if there is any change before laying out any huge sums of cash.

KF2M

Just to expand if you let off the gas, and it smokes then it's the rings. If you accelerate and it smoke then it's the valve seals. It's not concrete but it's enough to put you in the general area. I would do a compression test on all cylinders, and see if they are all within spec. If they are then I would suspect the valve seals. Have you checked your sparkplugs yet? I wonder if you might have a blown head gasket. You said it was at times intermittent, and the oil is low.

sycoglitch

Question, what engine does the overland have. I've heard that some of the WJs with 5l engines and up have an issue where the valve seals come loose. Do a google search. Happens I think with the 3.9, 5.9, and 6.1 with jeeps, dodge and some other vehicles. Not sure if it was an official recall but when hanging around my friend shop an engine rebuilding company came through with this issue and a video.

pkess3

I am going to check into this today. I've heard the PCV valve is fairly cheap and can be had at a local auto parts store? One thing interesting to note is that yesterday there was no check engine light and no blue smoke coming from the tail pipe. Might this inconsistency be a good indicator that it's just something like the PCV valve?

Good info, thanks! I really should do a compression test. I do not have this equipment but can probably find someone who does. Spark plugs are up there on my list of things to do for sure! I sure hope it's not a blow head gasket!

This 2004 Overland has the 4.7L High Output V8. I'm not sure if that recall applies to it but thanks for the info!

pkess3

Just as a follow-up to my original post, I did replace the PCV valve. There appeared to be a tiny bit of oil in the hose leading back to the engine. When I did this, I ended up breaking the brittle rubber end of the hose and had to buy a new one from an auto parts store that didn't exactly fit but with a couple of hose clamps, appears to be doing the job.

Ever since the original huge cloud of blue smoke that I experienced on my first full day of owning this Jeep, I have only seen it blow blue smoke one time since and that was on startup, right after driving it for about 20 miles across town. Does anyone think that this might be the valve guide seals since it happened on start up this time around? I have been checking the oil at regular intervals and it doesn't appear to be losing any oil. I recently changed the oil, using 6 quarts of 10W-30 synthetic and it appears to remain on the high end of normal oil level.

Just this morning I noticed the engine knocked for a few minutes after a cold start. I'm not sure if this means anything but the oil level is still in the normal range. Any thoughts??

tyler_zj

sounds like crank case pressure