Hello all,
Been a fan of XJ's for a long time and finally bought myself one. A 1998 with 150k miles.
As I'm getting familiar with the jeep and fixing things there's an issue with the exhaust emitting a lot of white smoke. I'll try to lay it out the best I can.
So when first starting the jeep in the morning it will smoke A LOT out of the tailpipe. After about 10 minutes it will mostly stop. However, if I turn the Jeep off and let it sit for a few minutes (still up to operating temp) and then start it back up, it will smoke some more.
I did a block test, sniffing the overflow reservoir. No color change.
I did a compression test on all cylinders, all were between 160-175.
Coolant is very dirty, definitely hasn't been changed in a long time but no sign of oil.
​​​​Is it possible for coolant to be getting into the exhaust and not show a sign on the tests I did?? Or does anyone else have an explanation or experience.
​​​​​​Is it possible it is smoking from excessive carbon buildup over the years?
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White smoke (make sure it's not grey-ish) is s sign of water in the exhaust.

It could be just condensation in the exhaust. This usually burns off after running a bit at full operating temp. This sounds a bit like what you are experiencing. You could have a bunch of water sitting in the muffler.

You can also stick your hand in the smoke stream until some of it condenses on your hand (be careful not to burn yourself) and smell it. Does it smell like coolant?

You could also try a pressure test on the radiator. You can "rent" the tool at pretty much any local auto parts store. Basically you pump up the radiator with a handpump and watch the pressure reading. If it drops, you have a coolant leak somewhere.

You should retry the block test but use the radiator and not the overflow.

Otherwise, just watch your coolant level and see if it drops after a while.

 

Not to insult your intelligence, but are you sure it's not just the usual steam from the exhaust that happens in cold weather?

 

I will definitely try re-testing via the radiator
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That's what I thought at first but even after the Jeep has gotten up to temp it will continue to lightly smoke, and if it sits for a few minutes off, once you start it back up it will smoke worse. As if something is leaking into the exhaust.

 

Hmmmm. That does seem a little strange.

 

My current thinking is that the issue could be oil related as I don't see any evidence of coolant getting into the exhaust. Maybe the valve stem seals are bad or valve guides, and are seeping oil after shut off. Does anyone have any experience with this?
I am debating buying a carbon cleaner, like BG dynamic engine restoration and giving that a shot, maybe a significant carbon buildup is preventing the seals from expanding or something.

 

White smoke [not steam] is likely burning oil. With the shutdown/restart I also thought of valve seals. I'm a huge fan of 'reading' spark plugs to see what's going on. There may be decent online guides, but I use an antique Motor manual, with pics and description of each problem. My nose is a decent analysis tool, too, for either exhaust or plugs.

With that mileage and evidence of poor maintenance, the range of potential problems is sizeable.

 

I pulled the plugs, I'll include a picture.


I looked into the valve cover through the oil fill hole and there is no carbon build up, it was actually clean. I am getting air bubbles in the coolant reservoir, not sure if air is trapped in the system or something more deviant. I have used a "block tester" to check for combustion gas in the reservoir multiple times now and never a reaction.
I've sniffed the exhaust a couple times but I don't think I would be able to tell the difference.
Current check engine codes are: p1494 (evap ldp) and p1282(fuel pump relay) I assume both are unrelated.

 

Summary of issue:
excessive smoke from tailpipe on cold starts, smokes heavy (white smoke) for about 10 minutes. Smoke will stop completely. If vehicle sits for about 30 minutes it will start the process over again even if still around operating temp.
Summary of conditions:
Check engine codes: p1494, p1282. Both seem unrelated.
Oil pressure gauge reads good pressure
Compression tests shows between 160-175 on all cylinders
Block tester (blue liquid tester in overflow reservoir) does not indicate combustion gas in coolant.
Bubbles are present in overflow bottle, air may be trapped in system as radiator cap was loose.
Oil is clean.
Not sure what to do next, valve stem seals come to mind but the smoke is definitely not blueish.