Superhero

1992 I6, 173k on the engine. I have no idea what kind of maintenance was done before I got it at 171k. I did a full tune up as soon as I got it home.

It smokes when you start it up, once it warms up no smoke, though there is an "exhaust" smell at all times. It smokes especially bad at start up when it is cold outside (or it might just be my perception), but even when below freezing the smoking stops once everything is warm. Engine has no trouble starting in cold weather and gets ok mileage and has good power. Oil looks clean. I threw in some Valvoline 10w-40 high mileage when I first got the Jeep to flush the system. Put about 2k miles on it since and am about to dump the oil and put Mobil 1 in. My manifold is cracked and the muffler is shot - dunno about the cat but I'm guessing it is fried as well.

No apparent oil leaks anywhere. Possible RMS or valve cover leak but if there is one it is less than a drop a day. The ground under my Jeep is spotless.

Burning this much oil is a concern - is there anything I can do to figure out if it is just the valve guides or if it is the piston rings? I am going to drop in a new engine ASAP (rebuilt or reman) but money won't allow that until August at the earliest, so keeping this engine running well until then is important.

Thanks!

Xjay98

My Big block chevy was doing that. Sounds like leaky valve guides/seals. You have oil sneaking through the valve stems. When you shut the truck off and let it sit, the oil collects in the chamber, walls and piston. When you fire it up in the morning your burning up that collection of oil. You're still burning oil when running but not alot since everything is moving.

Check your air filter too. If it has oil on it then you have blow by. I had crazy blow by on my 88 and never had smoking issues at start up.

Just keep her lubed up till Aug..

Superhero

Yeah that's pretty much what I was thinking.

Would it be possible to simply replace the valve stem seals and maybe the valve guides without pulling the head? I would need an air compressor to hold the valves up wouldn't I?

I'm going to top the oil off tomorrow and check it again in a week or two to see just how much oil I'm burning. What would be considered "a lot"?

Is there a risk of worn seals and valve guides causing a dropped valve or some other catastrophic engine failure?

Thanks for the reply!

Xjay98

I would pull the head. More work but its easier to work on it the bench. Not sure what type of valve seals the XJs have but if it is the positive style then you would have to go to a machine shop. I may be wrong... Honestly if you have 300 to spare you can get a fresh cyl. head from EvilBay. Then in Aug buy that short block.

To me half a quart a day is a lot. No worries on dropping a valve. You have the retainers holding them. Catastrophic? All you're doing is dropping and baking oil..

Superhero

Not half a quart a day. I think around a quart every 750-1000 miles. Catastrophic as in dropped valves. If that isn't an issue then I can't think of anything else that might be from what is happening but it never hurts to ask for other opinions.

I haven't decided if this issue is worth the effort of pulling off the head. I am gonna try to get a better idea of how much of an issue this really is before I mKe that decision. I do agree though, in the end pulling the head would probably be the easiest way to do it.

Thanks for the info!

96tudor

It's sounds like a textbook case of worn valve stem seals which can be replaced without removing the cylinder head. Pressure from the combustion chamber while the engine is running keeps the oil from traveling down between the valve stems and the guides. IMHO, I'd change to a normal API/ASE certified 10w-30 oil for high-mileage engines. Then I'd determine exactly how much oil that you're actually using. At that point, you can plan a course of action.

Oil consumption is not detrimental until the spark plugs start fouling, and spark plugs are cheap and can be purchased to work in a hotter range.

Forget about replacing the rear main seal and even the valve cover gasket if you do decide that you really want to replace the engine this year. Remanufactured engines come with new seals and gaskets. Those leaks aren't "pressure" leaks, so they don't pour oil in most cases.

From you description, I feel confident that your engine will last much longer than August as is. If oil consumption turns out to be a quart every 750-1000 miles, do a total engine evaluation. Check cylinder compression, listen for noises that would indicate worn bearings, lifters, etc. Check oil pressure with a gauge. If the bottom end is OK, you may only need, at most, a valve job which is also a good time to replace the exhaust manifold (which, by the way, may be where the exhaust smell is coming from).

Just don't throw the baby out with the bath water.

2Evil4U

I'm with everyone else and betting on the stem seals. (And for reference, and brand new BMW R1200GS motorcycle is rated to potentially consume a liter of oil /1000 miles. (Mine never did, but if they do they say don't worry about it.)) Just keep it topped up and run it.

Xjay98

As long as she's lined.

Superhero

You know, when I got it it was knocking like hell. When I was replacing the plugs I found that #6 was black, corroded to the point of barely having much of a plug left and covered with oil. The other plugs showed normal wear, though it looked like they hadn't been replaced in a long time. At first I thought the plug might have gone bad, causing the knocking, but in retrospect maybe it was the oil causing the plug to foul. I need to pull the plugs anyway and check them out to make sure all is well so I'll get that done this afternoon.

I was going to do just what you recommend and change the oil to Mobil 1 10w-30 this weekend and monitor the oil usage.

Yeah, I'm definitely not bothering with those seals and gaskets if I'm gonna replace the engine. However, if you're right and I can keep the engine longer I may do as suggested and pull the head and completely rebuild it. The only problem is I was just quoted $925+tax for a 3 angle valve job, clean, plane, port and polish. I'd be better off just replacing the whole engine at those prices, which is why I initially wasn't even considering just a top end rebuild. I might be able to find a reman head with zero miles for cheap somewhere - I need to do some research. I wish I could afford to replace it with a Hesco aluminum head...

I'll check the compression this weekend, and I'll pick up a mechanic's stethoscope too so I can really listen to it. Trying to pinpoint specific sounds on this noisy engine without one is impossible. I'm listening for whining, clunking and ticking noises from the bottom right? I have an idea what to listen for, but don't know exactly, if that makes sense. I've never had a car long enough for a bottom to go bad.

Thanks!

Superhero

What do you mean? Are you referring to a lined cylinder?

Superhero

I pulled a couple of plugs today. #6 is heavily fouled, oil and ash all over it as well as what looks to be some corrosion and blistering. The engine is starting to get harder to start as well, and I have no doubt cylinder #6 is the culprit. This plug has <2k miles.

Superhero

Here is the plug from #3. A little ashy, but I think that's from tossing a bottle of seafoam into the vacuum line. Otherwise to my eye this plug looks fine, if maybe a tiny bit hot.

HCCAFan

When I had to replace valve stem seals, mine would smoke after idling for a long time.

2Evil4U

Adding those pictures and the knocking to the information pile, I'm very interested in knowing what the #6 compression is compared to the others.

Superhero

Me too. I'm gonna test it as soon as I can get a compression tester and I'll post the results. I'm trying not to drive it until I have a better idea of what's going on. It has been running great (great to me, but I have no experience with the 4.0) but with that plug getting fouled so quick it's just a matter of time before it fails and it starts knocking. I'd prefer to avoid that.