Join Date: Jul 2007
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Why is oil blowing out my dipstick tube?
I have built a few dozen engines of various types over the years and have done all my maintenance all my life but I seem to have a problem I can't figure out!
1977 CJ5 4.2L engine. All seemed fine until I replaced my PCV valve during a regular oil, oil and air filter change. No reason, I just figured it couldn't hurt. Well a short time later, I noticed a lot of oil drips in my garage. I figured the PCV was wrong and went back to the store with it and sure enough it was. I got the "right" one this time but I still have a problem.
Now here is where it gets a little funny. Not ha, ha funny either. I cleaned the engine block with brake cleaner so it was clean and dry. I cranked the engine, manually set the auto choke high idle cam on the highest idle speed and left it running for 1 1/2 hours. I came back and not a drop of oil on the engine or the floor. By the way, all the oil wetness is around the dipstick tube. So, I drove it .8 miles to my buddy's gas station and back and the engine was soaked in oil from the dip stick tube back. I cleaned it off again and this time I removed the dipstick from the tube, fitted a rubber hose about 2 ft long over the dipstick tube and ran it up to a little empty plastic can and did the 1.6 mile round trip again. There was several ounces of oil in the can that came out the dipstick tube, through the hose into the can!
I revved the engine several times and could not get a drop to come out. It only blows out the dipstick tube when the Jeep is actually moving down the road. This is freaking me out! I can do nothing to cause oil to blow out the tube sitting still. By the way, I didn't exceed 25 mph to the store and back and drove at normal engine speeds.
My first thought was a broken compression ring creating pressure in the crankcase. But if this was true, the pressure would be created whether or not the Jeep was moving or not. Right?
Today I replaced the PCV valve again. I put a new oil fill cap on. I checked the PCV valve for a "rattle". It rattles. I cranked the engine to see if vacuum was present at the PCV valve and it is. I have good vacuum. I have good oil pressure, about 40+ at speed.
Any one got any ideas??
29,000 mile 'Barn Find" 1977 CJ5, P/S. P/B, 4.2L, T18, Dana 30 front, AMC 20 rear. I added: 2 1/2" Superlift lift, 31X11.50 SuperSwamper TSL's, Lock Right Front and Rear, Mile Marker E9000 and one piece rear axles