96 xj, 167,000 miles, recently home rebuilt motor, anyways; today I was on the interstate for an hour going about 80 mph the whole way (this isn't the unusual part). Near the exit where I was going to get off, I noticed I started a small loss of power (even though my foot was on the gas pedal). I drive another minute, then the smoke starts coming into my jeep's cabin from the gear shifter area. I immediately pulled off to the side of the road. I looked underneathed my jeep, and oil was all over my bellhousing, exhaust (which caused the smoke in the cabin), starter, and oil pan; pretty much anything on the lower distributor side of the motor. About 1/2 a qt leaked out overall. After about 10 minutes on the side of the interstate, I came to the conclusion that oil was blowing out my rear main seal. I pulled the line from the valve cover that goes to the intake manifold, trying to relieve some of the pressure of my crankcase. I drove the 10 miles home with no issues. So I gotta ask, wtf? This hasn't happened before and tomorrow I'm gonna reconnect the line to see what happens. Tell me what you think it is. Any help is appreciated, thank you!

 

Sopunds like your rear main seal is blown or ready to...the little line that goes from the valve cover to the intake is your CCV system and if its working right, should put a slight vacuum in the crankcase. Bad case senario, you broke a ring and something moved allowing compression gas into the crankcase blowing oil out, it may have moved back when the oil stopped shooting out. I'd do a compression test asap.

 

the ccv only functions at idle when running at speed like that the hose in the front of the valve cover that goes to the air box releaves the crankcase pressur thru the suction the throttle body creates it must go into the air box or aftermarket cold air intake tube

 

Interesting I though CCV stood for Constant Crankcase Ventilation? because theres no valve, just an orifice in a rubber grommet and the tube in front is for incoming fresh air. I can understand how it would ventilate better at idle though because you have more vacuum.

 

motors only create vacuum when at idle after that the intake system introduces air that why you have a vacuum ball in the bumper and a check valve on the brake booster to store vacuum

 

Hmm..They always make vacuum, motors are glorified air pumps. Just not enough at cruising speed to effiecently operate the booster or HVAC controls. I took my vacuum ball out and plugged my HVAC hose right to the intake and it still works even on the freeway, just really slowly. I don't know if you ever owned a vehicle with vacuum operated wipers, but they relied on vacuum even at cruising speed, granted they sucked, especially when going up hill(2K-3K rpm), but kick butt while going down hill(at idle). When a motor has no vacuum it stalls