I agree with stanf about the leak down test, that will narrow down where the pressure is escaping. Hope you have an air compressor. Just make sure you get that bad cylinder to top dead center before starting the test. If you get bubbles coming through the radiator, bad head gasket. Sound through the exhaust or intake, it's probably a bent or stuck valve. Through the crank case, could be a hole in the piston or bad rings. You should be able to listen where the air is escaping either bubbling or hissing. This is a reason why they sell mechanic's stethoscopes and I recommend you get one for the test too.
1989 Base YJ, 4.2l, Motorcraft 2150 carb, CRT HEI ignition, ax15, np231 JB conversions SYE, D30 ARB & Ford 8.8 ARB 4.56, 35x12.5r15 Goodyear MTR's, bds 3.5" springs, 1" body lift, and 1/2" Boom Shackles.
Build Thread: http://www.wranglerforum.com/f330/fi...ld-385106.html
Yes on the cylinder leak down test, but did you try oil in #4 and another compression test? By the looks of the blow-by and the sound in the video I really don't think you have a head gasket issue. By the way, congrats on the new baby..... That's my youngest next to me in my picture, she is 16 and wont stop asking to drive my JKU?
I put a little oil in it and got no results once again. I'm staring at it debating to just start tearing it down or not. I've checked places around here for a leak down tester and got stupid looks from people. I do got nothing but time to fix this. Money is a different issue. But do want to get her back and running normal as fast as possible.
Well, I guess my next thread has to be a rethread since it doesn't seem like the problem is what I was hoping it was. Going to try to get the head off tomorrow or the next day. Thanks for helping me get this far.
Are you sure it's a knock? I've haven't met a 4.0 that doesn't have a little lifter tick.. I can tell you that a head gasket job is pretty easy and just like you had done the basics before. I got here torn down in about two hours (and that includes taking pictures, labeling baggies and wires, put stuff in the baggies, etc) and put back together in a little less than four. Read up on how to do it and have a manual with you and you will be fine. A word of advice though is to pull the head, intake, and manifold off as one piece. It's a little awkward (and heavy for some) but man does it make it easy. Don't forget to get the head resurfaced and replace the manifold while your at it. Cause pretty much every stock one out there is cracked
I wish I would have followed your advice. Just got the manifold off and the bottom bolts were a PITA. That and apparently I had the 89 manifold on it. No room to play. My wife had the baby and it put me a little behind only getting about 30 minutes in a day. Head off tomorrow though.