4.0L woes

[JackstandJohnny]

so coming home this weekend from Waiparous Trevor informed me i was blowing blue smoke from my tailpipe, and i could confirm that i smell oil burning as well........... so somethings up with the 4.0L in the YJ

so: pulled spark plugs. there is no oil residue on them at all. they are actually burnt white (according to the Haynes manual, they are firing too hot?) and the electrodes are worn down. fair enough; needs new plugs.

did a compression test. she's 120 across the board cept for cyl.2. its at 85. haven't done a leak down test, but poured some oil in the cylinder and cranked it; compression went back up to about 100.

so, i've been told that ya, she is burnin oil, and even the head could be gone, as there is no oil residue on the plugs. so i guess, any ideas?

for the record i am also debating a V8 swap; throwing thousands into a 4L isn't exactley something i want to do......
any ideas?

i'v already talked to Jamey about this, but figured opinions don't hurt.......... usually.

cheers
John

[BlackYJ]

If it is blue smoke I believe that is a coolant leak, so you might need a new head

[FiEND]

coolant should be white smoke, oil blue, fuel black....?

[01sahara]

coolant should be white smoke, oil blue, fuel black....?

Yes, thats what I remember.


Does it blow smoke under acceleration or deceleration? Its been a long time but if I remember -under load look to the cylinder / rings, under deceleration high vacuum may be valve issue.  Many on the site with better and more up to date knowledge then I do so please correct me if I am wrong.

[JackstandJohnny]

under acceleration........... i can smell it on deceleration too. have a feeling the valves aren't exactely 'clean' either.  i only started to really noctice it this weekend to be honest. 

gonna seafoam it this weekend, clean the valves and take them out of the equation.

as for the coolant. i'm not sure the rads full as is the overflow.......... if it were burning the fluid level would have to drop right?

[BlackYJ]

coolant should be white smoke, oil blue, fuel black....?

Right, I have learned something new for today so I can go home

[dac]

I'm sure you can shoehorn a viper V10 in that...........


edit..... I think if the 5.0L swap is ok, the 351W swap would be better.  Easy and relitively cheap for parts and support.


and then you'd have the nice rumble of a V8 

[LifesGrand]

If it were grey smoke & only from idle & disappears during acceleration, it would be valve stem seals leaking... Doesn't sound like this is the case tho..

[dac]

under acceleration........... i can smell it on deceleration too. have a feeling the valves aren't exactely 'clean' either.  i only started to really noctice it this weekend to be honest. 

gonna seafoam it this weekend, clean the valves and take them out of the equation.

as for the coolant. i'm not sure the rads full as is the overflow.......... if it were burning the fluid level would have to drop right?

Burning coolant should also have a "sweet" smell to it.  Don't stick your nose up to the tail pipe though 

[FiEND]

"as for the coolant. i'm not sure the rads full as is the overflow.......... if it were burning the fluid level would have to drop right?"

when i saw a fluid leak it was quite a lot of white smoke but not much burning so may take a while to notice and the smoke is quite a bit under accel.  also saw lots of gunky poo colored foam along the dipstick.

[JackstandJohnny]

"as for the coolant. i'm not sure the rads full as is the overflow.......... if it were burning the fluid level would have to drop right?"

when i saw a fluid leak it was quite a lot of white smoke but not much burning so may take a while to notice and the smoke is quite a bit under accel.  also saw lots of gunky poo colored foam along the dipstick.

gotcha. oil is clean though. i'll check it again tonight, but it was ok. i'll get my neighbour to step on the gas a few times too and i'll see if it puffs blue/white/red/green/periwinkle blue/etc you get the idea lol

[frenchy]

cyl.2. its at 85. , but poured some oil in the cylinder and cranked it; compression went back up to about 100.

Worn Cylinder walls or piston ring in #2.

[cLAY]

Did you roll it? I saw a TJ in Moab smoke for 2 days after rolling it. Oil in the intake. Just a thought.

If it runs fine and has good power I'd run it till it gets REALLY bad.

[esi]

blue is oil. you might just have a chunk of carbon under n0.2 valve, give it a treatment and see if it clears up. I have a 400 hp.  327 that would fit inbetween the rails. It would probably need to be taken down and checked over. It ran in a test stand for 45 minutes then was stored for teh last 7 years. PM me if you're interested. 4.0L to 400 HP could be fun

[Corey Kruchkowski]

Worn Cylinder walls or piston ring in #2.

This is my call.