Probables:

1. Bad rings, real bad rings pressurizing the crankcase.
2. Pin hole in a piston pressurizing the crankcase.
3. Burned intake vavle and a bent stem pressurizing the crankcase.

That's all I can think of....

 

Thanks Leve, it sounds like a compression test should be added to the "to do list." The engine sounds fine and I haven't noticed any major power loss. Would I notice any other problems related to the 3 items you listed?
I did jack the vacuum lines around during the Weber carb install. Would that cause severe leaking? There was a discussion about how people are running the lines off the valve cover on their 258. I have a PCV valve on the front grommit, and hose coming from the front and rear holes tee'd into the air cleaner port. Any problems with that setup?


-=Rob=-

 

The vacuum line removal should not cause the pressurization of the crankcase unless the PVC has been deactivated or clogged. As for the setup using the front or rear gromett, that's a toss up in my mind... I prefer to run the pvc in the front. I also run a breather in the back and tee it into the aircleaner port. So far it works OK.

 

Going through the same problem right now! I fought it a while with no success. Finally took it to a shop. He called last night and said the dip stick tube is the likely source. Not certain the fix. Crankcase pressure is the cause he said. Should find out more today and I'll post it. Also, the 3 wire electric sensor at the oil pressure sending position may be cracked. Mechanic will do a "leak down" test and compression test today also. What a mess all over the right side of the frame, engine compartment and all that. Even the front of the little trailer I was towing is messy. Any other ideas? John

 

Adding to earlier post. This afternoon the mechanic called and still thinks the oil mess is from the dip stick tube. He said the oil in the crankcase is "fuming" - some thing to do with fumes? I didn't think to have him explain it. He is going to extend the dip stick tube somehow and then use a longer dip stick. I'll calibrate it next time I change oil. We'll see what happens. He also suggested I try a "racing motor oil" and the additives might help lessen the fuming. No other source of oil was found, the valve cover is good, oil sending units proved to be ok. Rear main seal doesn't leak. The new dip stick tube will be all the way up to about the level of the bottom of the valve cover. More later. John

 

Fuming?
Huh?
Does your mechanic speak english?
Does he know how to read?
Does he have any other customers?
Rescue your Jeep while you still can!

I don't usually get frustrated reading posts because I figure it's your money, time an Jeep. But this guy seems to be barkin' up the wrong tree at $45 or more an hour. You're your own best mechanic, fix the darn Jeep! There are two styles of dipstick tubes for the 258 engine. The first style is the one that I assume you have... it's short and comes up about 9" or so. You have to reach quite a ways to get to it. The second type comes all the way up to above the top of the engine. It secures to the side of the head at the same point as the distributor and points foward. It's got one heck of a long dipstick! This is the one I prefere. The tube is awful pricey at the dealer, and no one makes an aftermarket replacement. So go to your friendly Junk yard and pick up a tube off a Pacer, Gremlin, Hornet, Rambler, or any other AMC car that had a 258 in it. The last one I replaced was $10 for the dipstick and tube.

For goodness sake don't let the mechanic put in an aftermarket GM 350 Chrome Diptstick tube assembly avalialbe everwhere for $11.95. That's just plain silly, and then try to calibrate it later... It may fit, but use the right part.

Now as to the diagnosis... What the heck is "fuming?" Fumes don't carry raw oil with them and spew all over the engine compartment. An engine does not normally spew oil out even the short dipstick tube. Has he checked the oil pump, the filte for a clogged bypass, the fuel pump for a pin hole, a leakdown or compression test? Something tells me he's missing an important fact.

In the 20 plus years I've owned a Jeep the only time I've had the dipstick tube puke oil was two times...

Once when the tube was rusted through with multiple pinholes.
Once when the passenger side motor mount broke and the engine was leaning to the passenger side.

You've got a potentially serious problem that the mechanic is attempting to mask with a new dipstick tube or changing of oil. We're I you, I'd be "Fuming" at the mechanic for a rational explination. IMHO He'd better open his garage doors a little while he's working and get some fresh air to breath.

 

I've got the short dipstick tube that you described. I agree that the mechanic is not quite accurate in his cure for the problem. I had a TERRIBLE time at Naylor Motors in Ann Arbor (hint hint dont go there if you live in SE Michigan) They royally F#*@&$% me over. I don't have time to get into details, but it was a really bad situation. At any rate, I know exactly what John is talking about with the really messy side of an engine bay. I have to wear a welding shield to look at it because of all the glare.
John, plz keep us updated on how your ordeal works out.

-=Rob=-

 

Are you sure the mechanic didn't say "foaming"?? He may have intended to imply that some kind of foamation was causing your troubles.

Rob...when you say "tee'd to the air cleaner port" I somehow think that this is wrong. It would be ok if you said "tee'd to the intake manifold"(not a conventional hookup but would at least provide neg pressure in the crankcase). If you have it tee'd to the aircleaner where in the heck are you appling the manifold vacuum to the PCV valve? That is, if the "front and back holes are tee'd to the air cleaner port"??

or did I read this incorrectly??

GeeAea

Now that I've quit smoking my doctor informs me that I'll die in much better health!!!

 

The original setup had a hose coming from the aircleaner to the rear valve cover grommit. The idea being that clean fresh air is drawn across the rockers. The K&N filter has a fitting on the base to keep this setup, so I ran a short piece from there to a "T" fitting. Then I ran hose to the front and rear grommits of the valve cover. It seems like this would work. Do I need to have manifold vacuum on the PCV valve? Does that clear things up?

-=Rob=-

 

"The original setup had a hose coming from the aircleaner to the rear valve cover grommit. The idea being that clean fresh air is drawn across the rockers."

Thats a new one!

PCV or positive crank case ventilation valve is a check valve that allows manifold vacuum to scavenge crank case pressure. Excessive crank case pressure can cause gaskets to blow or leak.

The tube comming from your air cleaner is there to provide a path for other engine emmisions to be circulated through the engine and be burned.
My 2 cents

I have a jeep

 

Yes, you need to hook the PCV back up to the intake manifold and this will definitely reduce the amount of "spew" that you're experiencing. What you've basically done is forced all crankcase pressure to vent via the air cleaner(and anywhere else it can find an outlet).

If you still have uncontrolled blow-by I'd try and "tee" the valve cover to the intake manifold to provide manifold vacuum to both grommets/ports. Perhaps you can find a PCV valve that fits in the back port. Plug the K&N vent port.

GeeAea

Now that I've quit smoking my doctor informs me that I'll die in much better health!!!

 

SWEET! That sounds like a very logical and easy fix. So why does the factory setup have the aircleaner connected to the valve cover? I hope this does the trick because I really hope its not bad rings or other piston related issues creating the crankcase pressure.
Thanks for all the help.

-=Rob=-

 

Yes your PCV needs to be hooked up to full manifold vacuum

 

Well Rob, as someone here sorta said it's emissions related. They found out that 20% of hydrocarbon emissions came from the carb and fuel tank...another xxx amount came from the road draft tube. So they put tighter pressure/vacuum rated caps on the fuel tanks...ran a few hoses to charcoal canasters ... vented the air cleaner to the crankcase and vented the crankcase into the combustion stream for Positive Crankcase Ventalation. With injection the "carb emissions" are a thing of the past but the vent tube provides a convenient source of filtered air for the crankcase. BMW (at least my old 320i), among others, does not vent the crankcase. They use full manifold vacuum ...if you pull the dip stick ..it dies.

Re-pipe the pig and enjoy the tidy underhood view!/wwwthreads_images/icons/smile.gif

GeeAea

Now that I've quit smoking my doctor informs me that I'll die in much better health!!!

 

I am also wrestling with oil spewing out of the dipstick and out of the rear valve cover grommet / hose assembly which feeds filtered air from the the air box into the valve cover . I need to understand the " teeing suggestion " fully . Is the recommendation to provide manifold vacuum at both front and rear valve cover grommets by using two PCV valves ? If so, does the lack of feeding fresh air to the valve cover detract from the health of the engine ? Did I misunderstand the recommendation ?