Engine Rattle

OK, I have a rattle in my engine that's perplexing me. Originally I thought it was the alternator, but I replaced that and it's still there. I ran the engine with no serpentine belt and the noise was still there, so it's not in the accessories. I shot a video and am attempting to attach it to this thread so wish me luck. I really want to get this figured out because I'm going camping next week and need the jeep for the 300 mile round trip. I'd hate to take my KIA Forte to the campsite, it's just not the right vehicle. The rattle doesn't start till a little bit after the engine is started.

Thanks for any help,
Aaron

Can you tell us a few things: Is it an auto or manual transmission, how many miles are on this engine, and what is your oil pressure like?

Since you've ruled out accessories, a likely culprit of a rattling noise is loose flexplate bolts or a cracked flexplate if you have an auto. You should be able to remove an inspection cover (I've never done it, search for the procedure) and check the bolts for tightness and the plate for cracks.

Hopefully its not a rod knocking; if that were the case you'd expect to see very low oil pressure (with engine hot, oil pressure should be, i believe, minimum 13psi at idle). But the oil pressure senders are often flakey, so a mechanical gauge is the only 100% reliable method.

Hopefully others can help you more, but if you have an auto trans I'd definitely have a look at the flexplate; they are notorious for making all kinds of deathly sounds.

Good luck- Rob

A few simple things you can do is one, take off the oil filler cap and see if the noise is louder. Get your ear near the oil filler hole, be careful of rotating parts (real careful).
Get a handy length of pipe and listen to certain areas. Repeat, take a break, then do it again. Underneath also, along the pan seem and near the bell housing. It took me awhile, but the first time I was chasing down a rod knock, I managed to narrow it down pretty closely.
Injectors can get pretty loud.
That on and off knock could be loose flex plate bolts or a cracked flex plate.
Rod knock usually changes some from a cold to a hot motor but is often fairly constant and rhythmic. Changes with RPM.
Piston slap usually is worse at idle and mostly disappears at higher RPM's.
You can try pulling one plug wire at a time to see if anything changes. Usually best to do at the distributor cap. But can sure enough be a shocking experience. Rubber golves and not putting your crotch against the fender are advised.
You can get a good idea of how the top is oiling by looking down the filler hole with a flashlight. You can see some oil flowing and some drops flying around.
My first impression was a lifter or a rocker, but that should be easy to localize, listening in the oil filler cap hole.

It's an auto, 140000 miles, holds around 40lbs of oil pressure at all times. I changed the oil a few weeks ago and put in 15w-40 and a quart of Lucas to try and quiet it down. Didn't work.

I took it out today and put about 30 miles on it. It does not make the noise when under a load in gear. Even idling at a stoplight it really wasn't making the noise.

Is there oil inside the inspection plate or not? I just need to know before I drop it and have a gallon or so of fluid fall out.

Thanks For The Help,
Aaron

there is no oil inside the bell housing, it's just a shell surrounding the torque converter.

But the inspection cover is always oily from the rear main seal leak, that every 4.0 engine seems to have.

and your knock sounds like converter bolts, or a cracked flexplate. they sound quite similar, I've had both

I can say from experience that the noise is most likely not rod knock - it's way too erratic and doesn't seem to stay consistent with the changing RPMs.

Bigger_Is_Better said:

It's an auto, 140000 miles, holds around 40lbs of oil pressure at all times. I changed the oil a few weeks ago and put in 15w-40 and a quart of Lucas to try and quiet it down. Didn't work.

I took it out today and put about 30 miles on it. It does not make the noise when under a load in gear. Even idling at a stoplight it really wasn't making the noise.

Is there oil inside the inspection plate or not? I just need to know before I drop it and have a gallon or so of fluid fall out.

Thanks For The Help,
Aaron

Click to expand...

The inspection plate isn't sealed, so much oil at all would drip.

You really can't see anything (much) taking the inspection plate off. IMO it's better to get a piece of pipe or a stethoscope and listen. Narrow it down as much as possible before you start taking stuff apart. You can see the torque converter bolts but the center of the flex plate and the center bolts are mostly hidden.

I'll try the pipe trick as well, I've got a piece of 1/2" conduit I keep in the tool box.

Aaron

I have a xj with the same noise - i am still trying to run it down... i am going to look at flexplate first ... really annoying at idle... i do not think it is internal - i will post up when i find out more - also i will take a vid to make sure we have similar noise... oh 97 xj about same millage - 150k

that is the exact same noise i have.....can't figure it out either....

That sure sounds like "pinging"!

That is how mine sounds. My catalitic convertor is disintegrating. What year is it?

I don't think "pinging" is the sound we're talking about....you don't hear that loud rattling???