raycergurl87

Hey all,

I recently bought a 2001 XJ this last December with 130k miles. Everything was great until recently. Once it gets warm the oil pressure drops when I come to a stop and there is a ticking/knocking that I can't place.

The pressure used to sit about 40psi at idol and when warm, about 50psi around town, and about 60psi highway. Now when its warm and when I stop it sits 20-25psi, about 40-50 around town, and about 50-60 highway. I had the pressure sender go out in March and I replaced it. I was wondering if this sounds like an oil pump/oil flow issue?

With the ticking I can't tell if its a rocker, lifter, exhaust leak, rod knock etc, but with the oil issue I figure they might be related. It does seem to smooth out/ get quieter after about 2000 rpm and then comes back when the rpms drop. I can't pinpoint where the sound emanates, either on top or underneath. I also think my ears are playing tricks on me because some days it sounds louder and others quieter.

I had just recently changed my oil and would really love not to have serious engine trouble like a rod knock.

Thanks

Radi

20-25 PSI at idle is pretty respectable. Half that would be fine. Might check with a mechanical pressure gauge to make sure your sender isn't lying to you. Aftermarket sending units aren't always accurate. (nor are the OEM for that matter, but they're usually closer)

What do things look like under the valve cover? Any sign of sludge or other sticky nastiness? Peeking into the oil fill hole with a flashlight should be sufficient.

Rod knock is normally more of a deep thump than a tick. Noisy lifters can quiet down with rpm because of the increase in oil pressure..and the 4.0 could probably trademark the noisy lifter issue.
A stethoscope made out of a short piece of tubing might help you localize the noise.
Can you record and post the sound?

raycergurl87

I peeked through the oil fill and everything looks super clean. There wasn't any gunk or build-up. Nothing even looked sticky and the oil was still clean from my oil change. I did try the trick with the screwdriver to the ear. The loudest point seemed to come from under the valve cover. Approximately about half way back.

I also did a bit of snooping to see if there was anything underneath that could be the culprit because the noise has started to sound breathy. I wanted to check out the exhaust just in case. There is flaking rust that seems to have enveloped the bolts at the cat/tailpipe flange, but the rest looks ok. I probably need to do a better inspection during the daylight.

I did notice that my diff breather hose had a gaping hole worn in it and I am not sure how long its been this way. Didn't know if prolonged exposure could cause issues?

I currently don't have the capabilities to put up a sound bite. i will see if a friend can come by and help me with that. Thanks!

racebum

do an oil change with 20-50w oil and see what happens. it's summer which is the best time to run thick oil if you have to. using 20-50 will increase your oil pressure between 10 and 15lbs. if it quiets your knocking noise....well...if it's rod knock the clearances are getting worn. if it's tappet nicking you start wondering about the oil pump

letsgomuddin

X2, Im currently running 20W50 in mine diagnosing a similar problem, tho with no change and no pressure drop, mine proved that it's probably a cracked flexplate!

raycergurl87

So an update on my ticking... It looks like it's the flexplate. It started getting rougher and louder and it was loudest from the underside. It sounded a slight breathy sound so I figured it could possibly be the exhaust manifold. When I took it to the shop to have the leak located they said that the sound was coming from the tranny. It's currently in getting the flexplate replaced. I'm really sad that I don't have the resources to do it myself. I would prefer to work on it, not big on shops and such since I've been doing all my own work before I started driving.

Do you all know if a broken flexplate can cause damage to anything else inside the tranny?

I'll let you know how the repair works out. Thanks for all the help! It really makes a difference to have a network for assistance like this!

cruiser54

The broken/cracked flexplate should not damage anything else when it fails.