Noisy rod bearing?

eligunn · 02-23-2003, 10:34 AM

I've got a loud tapping sort of sound that just reared it's ugly head, it sounds mechanical like it has to be coming from the engine or the bellhousing. It only makes the noise under load and more so if I've got someone riding with me. I can't hear it too well if the car is just sitting still while I rev the engine.

So I'm hoping there's not too much damage. I thought it could possibly be a loose flywheel bolt, but either way I'm going to drop the engine. I've also got a slight vibration at about 27 to 31 rpms thats been there ever since I've owned the car. Sometimes the noise seems to coincide with this vibration but it doesn't really all the time.

Whatever it is it's extremely throttle position sensitive, like when I hear it and I just let off the throttle it disappears and if I give it a little more throttle it abates as well. It also seems to get slightly worse as the engine warms up but not very significantly so. It seems like when the throttle is right in the optimal position for holding a steady speed is when I hear it most.

At first I thought it might be an exhaust leak or rattle, but this does not seem to be the case. Any tips or hints would be much appreciated.

Thanks

stuart931 · 02-23-2003, 12:18 PM

you could possible isolate this noise within the engine by systematically shutting down one cylinder at a time. remove one plug lead at a time and place a spare spark plug into the laed and place this against the engine. run the engine and maybe load it up in gear with the hand brake on and the clutch slipping. if the noise is in the dead cylinder it should diappear during the test. move from cylinder tio cylinder to isolate the source. if the noise is still present thru all these tests it could be elsewhere , say in the camshaft drive or cam bearings. it could be a lifter going away . it is worth having a respected enfine reonditioner have a listen. you can also make a stethescope from a length of fuel hose with a bolt stuck in the end. lace the metal of the bolt against the engine block and the open end in your ear. carefully move the sensor end around the engine. don't be alarmed the noise is remarkeable but you may be able to locate the exact region the noise is coming from
stuart

highboost951 · 02-23-2003, 03:18 PM

If it gets louder as the car is getting warmer, it's because the oil is thinning and the cushion on the rod journal is disappearing. Sounds like a rod bearing to me, don't run it anymore to diagnose. Drain the oil and check the drain plug, any metal sludge or a nice little x-mas tree of shavings on it? Obviously if so, you guessed it right. As for your vibration, could be a few different things, I don't know what year or model you have but it could be as simple as incorrectly timed balance belt or a disentegrated rubber centered clutch disc. When they start breaking up, little junks of rubber start getting lodged into the pressure plate outer circumference and throw it out of balance.

profssr2017 · 02-24-2003, 06:43 AM

A rod bearing will typically make noise all the time - even at idle. I would recommend that you either make or get from an auto parts store (or Sears) an automotive stethascope. These things are pretty helpful in locating bad bearings, etc. Should only cost $25 or so.

I noticed that you said the noise gets worse as the engine warms up - what readings are you getting from your oil pressure gauge?

A disintegrating rubber centered clutch disk is very good possibility - when you are holding the throttle at a steady speed, the load on the clutch is minimal - with both slight accel/decell actions - this allows the splines of the clutch disk to rotate back and forth. Pulling the clutch inspection port on the bellhousing may help ID.

Good luck.

eligunn · 02-25-2003, 04:46 AM

It's got a new spring centered clutch, which I installed myself.

Yeah, at first I didn't suspect a rod bearing because my past experience with rod bearing noise was I could hear it rattling just by standing over the engine revving it with my hand. But that was on a different car, and the noise was really bad by then.

I've put about 200 miles on this car since the noise was first audible, and then it was just a mild clicking more so than a tapping rattling that it's turned into.

I'm not driving it until I figure it out. I'm just hoping the crank doesn't have to be reground or replaced.

I've pryed around on the exhaust trying to determine if it was a rattle or exhaust leak, but got no feedback from that.

And like I said the last time I drove it , when I first started it up and let it idle I couldn't hear anything, I revved it up and still could only hear maybe the soud of the lifters and the camshaft just a little, nothing too offensive.

But then as soon as I drove it as the rpm rose up past 2k I started to hear it again. And it's noticeably worse when my fat friend was riding with me.

So basically what I'm trying to decide is whether or not to go ahead and drop the engine out to try and find and fix whatever is wrong.

eligunn · 02-25-2003, 04:52 AM

Oh yeah, my oil pressure gauge always functions in a seemingly accurate and reliable fashion.

However my oil level light does not and has not for sometime now. It seems to start blinking sometimes for no reason. I check the dipstick and the level is about right in the middle between the upper and lower marks. So I add a little bit and it goes away.

Is it possible that my oil level light could have been trying to tell me I had problems even though my pressure is good and there's no visible problem by looking at the dipstick?

highboost951 · 02-25-2003, 06:05 AM

You can still have good oil pressure w/ a bearing on the way out. When you replaced your clutch, did you replace the pressure plate? If not, there could still be chunks of rubber on the inside of it slung to the outsides. Oil is cheap, have you pulled your drain plug yet? It's magnetic and will show you what's going on in your motor. Not many may tell you this or even suggest it, but I and some others have seen rods spin w/o actually damaging either the rod journal or rod/cap. If the metallic isn't too bad on the magnetic, drop the pan and pull your rod caps and inspect everything. By the sounds of it, you're at the early stages of the failure and it actually may be reversible w/o a serious overhaul, (those 200 miles didn't help though). If there's a lot of metallic, you've got to remember that it has possibly been circulated throughout the motor, but by the sounds of it, most likely not. Good luck.

eligunn · 02-25-2003, 10:53 AM

I did everything when I did the clutch, so there's no problem there except for the possiblilty of a loose flywheel.

I haven't checked the drain plug yet, but as soon as the snow melts I will.

I'll let you know how this develops, and I'll be looking for some advise on how extensively I need to tear apart and clean up the engine.

Thanks for the snappy responses, highboost.

So what is it that makes the flashing light come on, even though theres plenty of oil in the engine?

highboost951 · 02-25-2003, 12:47 PM

sorry I didn't really notice the post about your oil light, what year/model do you have?

eligunn · 02-25-2003, 02:04 PM

88 924S

chiefbrody · 02-26-2003, 09:49 AM

I had the same kind of symptoms as eligunn described above. The last time I drove the car it suddenly got louder and then died down the street from my house. I was first assuming it was a bad lifter or possibly a broken timing belt (haven't removed the cover yet to check), but after reading the above, I'm not sure.

Thanks for the help.

eligunn · 02-26-2003, 03:59 PM

Well here's the lowdown on my drainplug inspection,

There was a little bit of silver sludge on the magnet, as well as a couple of tiny metal filings.

The only really tangible one was trapezoidal exactly a 1/16 of an inch long about half as wide, and virtually 2 dimensional( no visible edge). This was by far the biggest piece and the only one I was actually able to isolate from the sludge.

I stuck my finger in the drain hole and scraped it around.
And was unable to feel anything or pull any chunks back out.

So, what I'm hoping is that I can get by without tearing the whole engine apart or removing the engine; yes, maybe?

Anyway I think I'm going to try removing the oil pan.

It really pisses me off that I've got a screwed up bearing. I thought I wouldn't be dealing with something like this for a long time.

highboost951 · 02-26-2003, 05:38 PM

Curious, how many miles are on your car? Be sure and get new rod nuts and the oil pick up seal too.

Britwrench · 02-26-2003, 05:42 PM

If you have a rod bearing out the engine has to be removed and stritpped, probably you will need another crank.

highboost951 · 02-27-2003, 06:27 AM

I don't want to start a debate, mislead anyone or give someone false hope, but usually yes and usually you should pull the motor; but if the journal is still polished and round, the rod's w/in spec, it can be done especially since if things are alright and caught early the amount of metal circulated would be min. and trapped. If the tapping was faint, you may be alright, if it was loud and scared the hell out of you, pull it.