mistertwister68 said:
Hey Thanks alot I really appreciate all this help! Any idea why all of a sudden this would develop a lifter knock? Could it be a bunch of sludge from the coolant/oil that let loose? Like I said I noticed this slow coolant leak for a little while before the lifters started knocking. Before that everything was running fine, temp, oil pressure ect. In fact when I drove it to the mechanics I had great oil pressure ect. He took the valve cover off and said my lifters (4 of them) had a quarter inch of play in them. Does that mean something else is wrong too (Cam??)
One other thing I also noticed was that even after my jeep got up to opertating temp (210) my rad cap would be cold.. Was this due to low coolant or ???
Thanks again!
Sounds like the lifters have "collapsed", and are no longer able to retain oil pressure.
Hydraulic lifters serve two purposes:
1) They take up the slack in the valvetrain. Hydraulic tappets replaced mechanical tappets (which were basically machined metal slugs,) and mechanical tappets required periodic adjustment to keep noise and wear down. Hydraulic tappets eliminated this. Slack is taken up by the piston in the top of the thing, and the retention of oil pressure inside the lifter body (take apart an old one, and you'll get a better idea. They're held together with a small snapring, and it may be easily removed with a small flat screwdriver.)
2) They pump oil up to the top end of the engine (by way of the hollow pushrods,) to keep the rocker tips and pivots lubricated. When the valve first opens, a small amount of oil is forced out of the top of the lifter, which makes its way up the tube of the pushrod to the top end of the engine.
A "collapsed" lifter (usually indicated by a ticking sound that doesn't go away within about a minute of startup) means that the lifter can no longer retain oil pressure - probably due to internal wear (parts inside the lifter proper.)
A lifter can also "go solid" - usually because it's packed with crud. In this case, it doesn't self-adjust anymore, and symptoms usually include a mild to moderate loss of power (because the valves don't close properly anymore.)
A "collapsed" lifter can cause trouble - as I mentioned, the valves are now "slammed" or "slapped" shut instead of properly closed, and that means that the valve heads can crack. Worst case? If it's bad enough, long enough (we're talking noise like shaking a box of hammers here...) the valve head can actually snap off of the stem and get lodged in the piston head. This is in the very worst cases (there is sometimes a hole in the valve cover as well - since the valve head is the other end of retaining the valve spring. The valve stem and associated parts try to leave the engine.)
A "solid" lifter typically results in burned valves (because they don't close all the way,) poor vacuum, increased HC emissions, loss of power, ... Solid lifters don't tend to be noisy, because they're not slapping valves shut (in the worst cases, the valves actually
do not close.)
At rest, expect there to be some small play in the valvetrain with some effort. For instance, you can push the plunger down (with some force) or spin a pushrod in its seat - but it should take some work to do (the "old standard" for adjusting the valvetrain on a Small Block Chevvy V8 was to turn the crank until both valves are closed, and spin the pushrod with two fingers of one hand while tightening the pivot nut with the other until you couldn't do it anymore. Our 4.0L engines, however, have fixed pivot balls - torquing the rocker screws down sets the preload on the lifters.)
If you're worried about cam lift, it can be checked with only needing to remove the valve cover - but you'll need a dial indicator with a magnetic base and about a couple of hours (you'll be turning the engine by hand and checking lobes one at a time.) A decent dial indicator and mag base kit can usually be had for <$50 via mail-order (check with Enco, MSC Direct, or any other MRO outfit - they're useful to have anyhow, once you get started on doing your own work. A 1" travel indicator is enough for most applications, I've not typically needed more than a 2" for most work. Checking strokes will require a 4" or so, tho.) Usually, however, the symptoms of a "flat cam" are rather more obvious - no need to worry about that, unless you've been using API "Energy Saving" oil or something like that (that's another discussion, believe me!)
Hm - cold cap on an "open" system? Do you have a non-contact IR thermometer? They can be had fairly cheaply - it may be instructive to idle your engine up to op-temp and then take a "thermal profile" of your radiator to check for blockage. That's the first thing that comes to mind for me...
