91 4.0 oil pressure

You have classic symptoms of low oil pressure, usually due to worn bearings. I'm presuming that the '3' on the gage is 30 psi. A rebuilt engine should pull a minimum of 40 psi even at hot idle. A lifter may be noisy but it won't drop the main oil pressure even if it is sticking.

If you have faith that the engine is properly rebuilt, I would do a couple of quick oil changes (500 to 1000 miles), use high quality, high detergent oil in a 10-30 grade for that engine. I'm not quite so sure you have a good rebuild. :(

The thermostat is acting completely normal, except that I would expect it to be up around 205F if you have the proper 192 degree stat. You mentioned a 'noticeable drop' in temp when the thermostat opens. Nope, the 'stat opens very slowly with increasing temp, it will modulate the temp and hold it within a few degrees.

jeepr wrote:

On newer engines the temperature has to stay above 190 or even higher for pollution controls to work right, and to prevent water vapor from forming sludge and acid in the oil. The engine temperature sounds find to me. What weight oil are you running?

Do you know what units those pressure readings are in? Three to six sure sounds low. I am used to getting 20 to 40 psi from a newish engine.

I would worry about the lifter. It might cure itself, but it might not. Either way, it shouldn't be making that noise now.

Earle

Could I just say your engine is running fine and don't worry about it. Go out and enjoy it. :O) I didn't think I could just say that, so see below.

Hi Earle, I was wondering why you think the lifter is a problem and what do you think will happen if it continues?

And either way, it shouldn't be making that noise now, you say?

As far as I know, any engine can make that noise at most any time and all it means is it's making a noise. Do you know something I don't? Thanks,

The engine was not rebuilt but sat for almost 5 years and was installed during the restoration of the jeep. The gauge I refer to is the one on the dash graduated from 1-6. The lifter drowns out the thrush muffler and is kind embarassing, I'd rather draw attention to the jeep for its looks, painted in and out in bedliner paint, looks awesome. Im just worried the lifter is not getting enough oil and want to a avoid a catastrophic failure.

I would also be very worried the lifter was seized with that much noise. A dry lifter will eat up things and a noisy lifter can pop out or punch through rockers. Rockers have even been known to fall off when loose on some engines. I have seen all that happen.

I think I would run a pint of ATF in the oil or a pint of kerosene or some other sludge eater for a few hundred miles.

One other option is to remove the valve cover and visually inspect them while it is running. A really good rap with a dead blow or rubber mallet while it is running can sometime free up a seized lifter.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00 'New' frame and everything else in '09. Some Canadian Bush Trip and Build Photos:

What's bugging me is it sat for 5 years. Little late to say this but you should have at least popped the head and oil cover to clean and prelube the engine. Could even be blocked oil passages. I hope you spun up the oil pump before starting the engine.

Mine makes a little rattle at idle and that is all it has done for almost

100,000 miles. When things made of metal are making a clicking, knocking or tapping noise they are smashing into each other and that only goes on for a little while before something gives. Of course you never know as much as the guy who is standing next to it hearing it, but if it went on for long enough to bother posting on the Internet, well then where there's smoke there's fire, «Cuando el agua suena es porque piedras lleva."

What it actually means, a little deeper than just making a noise, is that internal engine clearances aren't right. Now if you hold to the stuck lifter theory this may eventually clear up, but until it does it is something hammering on itself, cause for worry. It could bend a push rod, tear up the cam, maybe even make the valve stick. It's not "good" that it is making that noise, and in this business things that are not "good" are "bad". Nothing else they could be. Push rod could come through the rocker...

Earle

Ok Earle, I was wondering what your reasons were and they seem ok to me. My experience is all of the noisy lifters I've heard, I've never heard of any causing any problems, but I suppose they could.

Of course if some noise is bothering someone, the best thing to do is get it fixed, just so they can relax. Thanks,

When I got my 88 MJ, the poor old 4.0L six sounded like a sewing machine after a cold start. That, and a few other indicators, made the maintainence history suspect so I tried some short-cycle oil changes (1500 miles) adding a quart of ATF about 100 miles before the change. A fresh oil change quieted the noise some but it came back after a few hundred miles. After about 4 oil changes this way, the noise at startup would go away after a few secinds so I said "good enough" and went to regular oil changes at 3000-4000 miles - the longer interval when most of the miles were at highway speed on trips - and after 10,000 miles or so the noise was gone. I can only conclude that there was crud built up in the lifters that the ATF dissolved slowly. I've seen this in many engines over the years so I'm not surprised at the quieting. The one the OP described sat a long time - odds are it just needs the varnish/crud washed out.

NAPA SeaFoam.

Doug, I've seen that product several times - is it really that much better than ATF or kerosene used properly?

For cleaning out oil gunk buildup in the engine just before an oil change, yep. Had a local shop try it out on an engine they were going to pull/rebuild. Came out so clean they decided to make it a routine first step for any running engine.

I use it every other year in my ZJ. First time it looked like I was draining Guinness. Now when I drain the oil in my ZJ it looks nearly new.

Now if your talking de-carbon by the water/ATF dribble method I'd say water works just fine. ATF makes too much of a smoke screen. ;)

For a full injector/intake/exhaust clean I go to a shop that uses the MotorVac system.

Thanks, Doug. I'll have to give Seafoam a try. I've been running clunkers for more years than I like to count and my routine one a "new" one is to change ALL the fluids immediately and flush the engine. Kerosene works well for the engine but you have to be really careful, ATF works but it's slow - 2-3 oil changes - so this sounds like a worthwhile experiment.

I agree about ATF for cleaning the cylinder heads. Way back when, you used the old oil to settle the dust in the driveway and a lot of cars looked like they had a smoke generator in the exhaust. Nowadays, using ATF to clean the top end will probably get you an immediate visit from the fire department followed by the Health Dept. and the EPA - each with a six inch pile of forms to fill out.