Desertsandxj96

So while driving my jeep tonight, it started puking oil, i cant for the life of me figure out where! The only thing ive done to the jeep that isnt stock is an oil breather, i also recently replaced the pcv valve. Oil pressure was normal while driving but when stopped goes down below halfway on the gauge...
Any ideas or a common issue the 4.0 has with oil leaking would be appreciated as im new to the jeep world.

blazer 2008

oil filter adapter maybe

jburg318

You need to give more information than this. Area/region of the leak, pictures, etc.

Jeepwalker

Hard to say. Clean it off with cleaner, let it dry, and try tracking it down again.

Mine developed a mystery rust hole on the back of the oil pan 2" from the bottom. A little trusty JB Weld did the trick.

gat

You can add an ultraviolet dye and use specially tinted glasses to view the oil. Oil from the engine could come out of the filter, adaptor for the filter, closed crankcase ventilation tubing, the rocker arm cover, the output shaft seal, the timing chain cover, and the seal from the pan and block. If there is much oil and you can't tell flow or new versus old, then using the dye would help. You can alternatively clean these or the suspected areas, then start it.

Any additional details may be beneficial.

Desertsandxj96

I was able to tell it wasnt on the top of the motor or the front, nothing dripping from the oil filter adaptor, im going to crawl under it tomorrow and get a better look, oil psi dropped as it started leaking tho, looks now to be about 3 qts low

gat

3 q is half of capacity. You wouldn't see much oil on the end of the dip stick. Check the tightness of the oil pressure sending unit and that the oil filter is secure. 3 quarts doesn't seem like a gap in a gasket around low pressure sites...

Desertsandxj96

I apprecieate it, i will tear into it monday when i can get it into my garage, if its not either of those im just going to replace every gasket that could possibly leak oil except the rear main or any others i would have to pull the trans or the head for and see if it fixes it, 160k miles its probably time for gaskets anyway

gat

The rear main seal is replaced with the oil pan out. If you are replacing the oil pans seal, then you have created almost all of the access to replace the rear main seal. It is two pieces.

The rear main seal would leak into the bell housing of the transmission. It and a leak at the rear of the rocker arm cover gasket would produce a similar location for oil leakage. The rear of a head gasket is the thickest part by width. I don't think that that is a likely place for a leak in the head gasket at the rear.

Have you ever started it to idle with the hood open?

Idunno

Check the back side of the engine valve cover. That's the lowest (gravity) point on the cover and any leak will evade visual detection without a decent inspection mirror and light, which should be the first tools acquired to perform such an inspection anyway.

Note: Keeping the engine clean as a routine practice will negate the need to degrease years of accumulation to perform a failed item inspection/detection. Just saying.

arto_wa

I installed on of these and it appears to be a permanent fix. No more leaks from the valve cover seal - great reusable product and no need to mess with silicone etc.!

gat

It is very easy to remove the two screws on the distributor cap and look for oil under it. There should be none. Asking as you are there make sure that the rotor and cap don't have much wear on their contacts. There is no need to pull any of the spark plugs' wires for this. At most just pull the middle wire to the coil.

cruiser54

CRUISER'S MOSTLY RENIX TIPS

REAR MAIN SEAL DIAGNOSIS

OCTOBER 31, 2015 SALAD 2 COMMENTS

I’d be looking up ABOVE first, and VERIFYING the source of the oil leak YOURSELF.

Everybody, who doesn’t own or have to pay for or perform your vehicle repairs, loves to poke their noggin UNDER the Jeep and come out bearing the false bad news that your RMS is leaking. Many mechanics, friends, and good old Uncle Bob seem to enjoy telling you it’s the rear main seal. Has a catastrophic ring to it, doesn’t it?

A simple leak at the back of the valve cover or other source could produce the same symptoms. You don’t need to be a mechanic to figure this out. If you have good eyesight and a dim flashlight, you’re good to go on your own. Don’t jump on the RMS/oil pan gasket bandwagon right off the bat.

Almost any oil leak on your 4.0 is gonna drip from the RMS area for two simple reasons:

First off, the engine sits nose-up and any oil will run back to the RMS area.

Secondly, the RMS area is also the lowest point on the engine. Simple physics and the old plumber’s adage apply here: “Crap flows downhill”.

Valve cover gasket, oil pressure sending unit, oil filter adapter seals and distributor gasket, in that order, have to be eliminated as possibilities first. A little tip here. Rather than use a dizzy gasket, use an o ring instead. NAPA #727-2024. Tips 12 and 13 will help you get your distributor back in place correctly.

gw204

The 4.0 doesn't have a PCV. The CCV elbows on top the valve cover and just that...elbows. The forward one that routes to the airbox isn't metered, but I believe the rear one that goes to the intake is. Clean the oil off, inspect the stock CCV parts (check that the elbows and lines aren't blocked), put them back on if good and see if it still leaks.

If you put a non-stock pcv valve on there that's probably caused the problem.

arto_wa

Excellent point!
I guess we all had somehow missed the OP did actually say " i also recently replaced the pcv valve ".

Doh