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Unread 06-21-2009, 06:02 AM   #1
aerospace
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Blue smoke, valves maybe?

Hey guys,

My Jeep is blowing loads of blue smoke out the back (especially when pulling away). I had the CAT removed when this started to happen, although I think this is just coinsidence.

I am also going through a lot of oil indeed. I have to keep check and fill up a lot! So I assume im burning oil. Is this the valves? The car has 167,000 miles on the clock.

Do you think this is a valve problem? And how much do you suspect this will cost to put right, is it a big job?

Thanks in advance

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Unread 06-21-2009, 06:19 AM   #2
Tweaks
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The cat repair and the blue smoke aren't related. The blue smoke is certainly the oil that's missing on your dipstick coming out the other end.

It could be a number of things, but you won't know until you do this: A leakdown test. You need to get the whole thing checked out. I would start by getting a compression test on each cylinder and then getting a proper leakdown test to see if it's the rings or the valves. You will be able to hear the compressed air leaking past a closed valve if it's a valve.

If it's using that much oil you may want to forget about the leakdown test and just get it rebuilt because that's what it's gonna need.
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Unread 06-21-2009, 06:30 AM   #3
comptiger5000
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Does it burn oil all the time, but worse on acceleration (indicates bad rings), or is it mostly at first startup and on deceleration (indicates worn valve guides)?
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Unread 06-21-2009, 06:57 AM   #4
sdowney717
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oil control rings or piston drain back holes plugged.
you could try running 2qts of dexron 3 ATF mixed into the engine oil .
This solved a sludged ring pack on a saturn sl2 of mine. Is your engine sludged up? if it is when you look inside the vlave cover, I would suspect rings are sludged and cant control the oil flow.

I just rebuilt a 1998 4.0L and the rings were pretty clean. there are 6 drainback holes in the oil ring groove and they are pretty small. The valve seals were hardened but they still sealed the oil out.
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Unread 06-21-2009, 06:59 AM   #5
sdowney717
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the cat burns up some of the oil so oil burners are less noticed when driving. Take off the cat and it shows itself clearly. Friends Honda was a massive oil burner, but never showed any smoke. We figured the convertor was burning it all up.
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Unread 06-21-2009, 07:28 AM   #6
cmonson
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do a wet and dry compression test.

Report back.
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Unread 06-21-2009, 07:30 AM   #7
cmonson
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Usually blue smoke on acceleration is rings.

But as I said above, do a wet and dry compression test and report back with the numbers. If you don't have a gauge, you can borrow them from autozone.
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Unread 06-21-2009, 08:00 AM   #8
aerospace
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Hi guys, and thanks for all the much needed info.

I will defo have this checked out in the morning. I dont know if I want it to be the valves or the rings? Picking the best of two evils isnt one of my strong points.

The blue smoke just happens when...

I touch the accelorator for the first time to pull away from standing. And when I turn the engine on, there is a puff of smoke.

As far as I am aware (although not 100% certain) the smoke does not happen when I am accelorating whilst driving and does not happen when driving round. It was just strange that this happend as soon as the cat came off.

Will the job (rings or valves) cost much to fix? The word "rebuild" has been used a lot and I dont like the sound of that?

Thanks again, your comments are much appreciated!

Last edited by aerospace; 06-21-2009 at 09:13 AM..
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Unread 06-21-2009, 02:30 PM   #9
vansskaterfreek
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how many miles do you have?
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Unread 06-21-2009, 02:48 PM   #10
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Quote:
Originally Posted by aerospace View Post
Hi guys, and thanks for all the much needed info.

I will defo have this checked out in the morning. I dont know if I want it to be the valves or the rings? Picking the best of two evils isnt one of my strong points.

The blue smoke just happens when...

I touch the accelorator for the first time to pull away from standing. And when I turn the engine on, there is a puff of smoke.

As far as I am aware (although not 100% certain) the smoke does not happen when I am accelorating whilst driving and does not happen when driving round. It was just strange that this happend as soon as the cat came off.

Will the job (rings or valves) cost much to fix? The word "rebuild" has been used a lot and I dont like the sound of that?

Thanks again, your comments are much appreciated!
valve guides you have to pull the heads, rings you pretty much have to pull the motor.

when a motor starts smoking you do one of two things. full rebuild or drive it till it won't drive no more.
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Unread 06-21-2009, 03:18 PM   #11
baxy
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pull the plugs and see which hole have oil fouled spark plugs
did this oil consumption (not necessarily the blue smoke) start suddenly or have you been adding oil for some time?
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Unread 06-21-2009, 07:13 PM   #12
comptiger5000
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It sounds like valve guides if it only does it right after startup. To further test this, get up to 40-50 mph (make sure you have space behind you). Drop the transmission into "2" while coasting. You'll slow down fairly quickly. Watch for smoke behind you. Valves will typically smoke from the high intake vacuum of running 2500-3000 rpm at closed throttle.
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Unread 06-21-2009, 07:28 PM   #13
1995zj
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Plenum gasket or plate?
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Unread 06-22-2009, 03:21 AM   #14
aerospace
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Hi

Thanks again, I will try all of the above and report back. The car has 165,000 miles on the clock. The blue smoke does just happen on start up and when ever I pull away from a junction. During normal driveing (E.G. 30-40mph) cirt driving there is no smoke.

I have noticed the oil to be low a couple of times but I think this has just started happening to the car.
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Unread 06-22-2009, 08:31 PM   #15
vansskaterfreek
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Quote:
Originally Posted by aerospace View Post
Hi

Thanks again, I will try all of the above and report back. The car has 165,000 miles on the clock. The blue smoke does just happen on start up and when ever I pull away from a junction. During normal driveing (E.G. 30-40mph) cirt driving there is no smoke.

I have noticed the oil to be low a couple of times but I think this has just started happening to the car.
my guess would be on the plenum gasket...... very common on 5.2 if thats what you have, you never specified the motor.....
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2004 WJ 4.7L 107k miles - her daily driver, 2" daystar BB with scorpion shocks.. not too bad! stuffed 265/65/17 General Grabber AT2'S
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