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Smoking

Black_Black

NAXJA Forum User
Location
Colorado
Hi jeepers,

I have an 89' cherokee with a lot of under the hood smoke. It had a bad valve cover gasket for a while, so oil all over everything and the down pipe. It never smoked until I did some work including injectors and plugs now a lot of that is burning off. My theory is I was running rich before and now exhaust temp is higher? It has a relatively new ngk o2 sensor.

Anyways I replaced the cat and muffler and noticed the manifold / downtube gasket was very loose so I tightened that. My engine has always had a turbo whine like sound every so often, but now it's very prominent. It runs great..

Does that sound like a cracked exhaust manifold?
 
You have an oil leak and there is a whine. Are they related ? Probably not at all.

The most common oil leaks are valve cover, oil filter adapter, and rear main seal.

A whine is just a whine, transmission, power steering steering pump, or some other belt driven accessory.
 
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Well I've been watching it, I still have smoke rolling out from under the hood on warm days. I think all the oil leaks are fixed. My exhaust is still burning off some oil but I think there is something else. I keep smelling burning rubber and gas. I think the fuel lines are ok. Where do I start without firing the parts cannon?
 
The car wash, and then pay attention!
 
You have received good advice! I have some additional general advice.

On a typical engine, the lifters, valve stems, etc. are flooded with oil which then returns to the crankcase via drain holes in the head. On the compression stroke, the pressure expands the ring to keep most of the pressure in the cylinder for ignition and then the ring relaxes for the exhaust & intake strokes. A proper functioning ring is always expanding to hold pressure in the cylinder (i.e preventing most of pressure from entering crankcase) and relaxing to reduce friction. When a ring/rings are broken or the rings become "stuck-closed"(i.e. from oil sludge/carbon build-up), the compression pressure in the cylinder "blows-by" the rings and pressurizes the crankcase. The crankcase pressure, in turn, pressurizes the valve cover via the drain holes in the head. Result?
Oil leaks at the valve cover gasket, excess oil vapor being sucked into the throttle body for burning, oil enriched exhaust getting into the exhaust system etc. I would suggest the following;

1. Do a compression test on all cylinders. One or more low compression pressures could mean a broken ring or rings "stuck-closed". Cast iron rings DO break. Ductile iron rings or steel rings DO NOT break.
2. If all compression pressures are low, you may have rings "stuck-closed" and there are chemical additives you can add to the oil to free the "stuck-closed" rings. "Stuck-closed" rings are a common problems on ALL engines. Many "engine rebuilds" are sold to people on the premise that the engine is "worn-out". I once pulled a Chrysler V6 overhead cam Mitsubishi engine where 5 out of 6 pistons had "stuck-closed" rings. The reality is that a simple freeing of "stuck-closed" piston rings can regain engine power and give better gas mileage, etc. Obviously, a broken piston ring would need to be replaced.

Best regards,

CJR
 
I washed it and after some inspections I found more oil leaks and a heater hose leak. Thanks for the advice.

Here's the results of my compression test, what do you think?

1 140
2. 152
3. 140
4. 144
5. 137
6. 139
 
I would suggest trying to unstick/free the piston rings. Typically, the gunk that sticks piston rings closed are carbons,oil sludge, and lacquers from the gasoline. Gumout Carb Cleaner has two solvents that loosen this gunk.

My technique is to buy two(2) cans of Gumout Carb Cleaner. Pull ALL the plugs and with a small diameter hose spray all two(2) cans into the six(6) cylinders. Replace the plugs and let it set overnight. The rings will loosen the piston rings and then evaporate. Fire it up and you'll get some white smoke initially. The rings now should be unstuck/free and working properly. For "kicks and giggles" check the compression pressures on the cylinders again and see which ones didn't increase in compression pressure. Spray those cylinders again and repeat to see if that helped any. If it didn't help, those cylinders may have broken rings. This is a inexpensive trick to try, so repeat it a couple times to confirm broken piston rings. If this works and frees the piston rings, do this trick on a regular basis to maintain the power gain and better gas mileage.

Best regards,

CJR
 
Is it pretty much guaranteed I have stuck rings at 300k miles? I'm not mad at those numbers for the age and I have no problems with mileage or power. I'll try the carb cleaner if it's not going to hurt anything and test again
 
Whether or not you have stuck-closed piston rings is dependent on;

1. Quality of oil/gas that has been used in the engine.
2, How regular the oil changes have been.
3. Design of the oil drainback holes/slots in the pistons.
4. Remember, the "oil squirter holes", in the connecting rods, continuously spray oil on the cylinder walls to lube or cool the walls. If oil drainback to the crankcase is inadequate, excessive oil pooling/puddling around the piston rings occurs and the piston rings WILL eventually stick closed.

Some piston designs have an inadequate number of piston drainback hole/slots and stuck piston rings occur at low mileages. In custom forged pistons, with inadequate piston drainback holes, the oil "puddles" around the rings and the rings stuck after a couple thousand miles. In typical production engines, i.e. Mitsubishi OHC V6, 5 rings were stuck closed @ 80,000 miles. In my 88XJ, with the Gumout trick, NO stuck rings @ 384,000 miles when I rebuilt it. If you don't want to use the Gumout trick, use the oil additives (i.e. delivers diluted solvent to free the rings). Because the additive is added to the oil, less solvent is available at the rings so it takes longer to free the stuck-closed rings. These oil additives are sold because stuck-closed piston rings are a problem in engines.

Best regards,

CJR
 
No, it has never smoked from the exhaust pipe.

Thanks for the info, I have never thought about my piston rings. I like your gumout idea more than adding something to the oil
 
If you do the 2 cans of gum out, change the oil before starting the engine. IMHO not enough of the solvent will have evaporated to allow for safe engine oiling.
 
Pressure wash the engine, top and bottom. Hit the back of the head. It is common for the valve cover to leak down the back of the engine and masquerade as a rear main seal leak. If it starts again, check the back of the head and look for a hot part (exhaust header, down pipe, and exhaust pipe) that shows fresh oil.

My trick is to mix up some water with a small amount of corn starch and put it in a spray bottle. After pressure washing and getting everything degreased, spray down everything and let it dry to a white powder covering everything. Then start it up and watch for a color change.
 
I'm going to leave the piston rings alone, the Jeep runs very well. I'm glad CJR contributed though that's great information to have for the future.

Yeah I don't like the idea of solvent in my oil.

I think I found my leaks but the corn starch trick sounds very useful.

Thanks everybody I appreciate your time!
 
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