Another day, another problem. Weird engine noise and oil leak (Page 1/1)
Cliff Pennock NOV 23, 09:53 AM
After recently replacing the exhaust, radiator, heater core, and addressing various other issues in the past few months, I had hoped to be done with car repairs for a while. I was wrong.

After these repairs, I had only driven the car short distances, max 25 miles per trip. During these trips, there was no overheating, the exhaust sounded fine, and the only leak I knew of was near the radiator, specifically leaking transmission fluid. I know the cause, and it's a straightforward fix that I plan to address once the weather clears up. So, at that point, I was content with the car's condition.

However, after embarking on a more substantial journey (100 miles to and 100 miles from), issues arose. The outward trip was problem-free, but when I started the car for the return journey a few hours later, I noticed an unusual engine noise which I had not heard on the way there. From inside the car, it sounds like a potential exhaust leak, almost like the distinct sound of one or more cylinders "popping." It is quite noticeable. Interestingly, the noise is barely audible from outside the car, making me doubt it is the exhaust. Listening in the engine bay, it sounds more like a ticking noise.

Upon checking the oil level, I discovered it was extremely low - so low that it didn't register on the dipstick at all. I promptly added about two quarts of oil, but this had no effect on the noise. The following day, I observed an oil puddle under the engine, precisely where the oil filter is located. I haven't replaced the oil filter in approximately 15 years, so it's much overdue. During my last inspection under the car (when replacing the exhaust), I noticed oil seeping from or around the oil filter, leading me to suspect that the oil filter itself is the source of the leak.

Despite these issues, I haven't noticed any changes in drivability. I drive my car conservatively—no hard acceleration, and I never exceed 75 mph. Now, the question is, how can I pinpoint the cause of the noise and/or the oil leak?

I have added recordings (made with my phone) of the engine. It's much more noticeable in real life, the recording hardly picks it up. I have two versions of each recording. The original and one with a high pass filter applied to get rid of the low engine rumble.


Original from within the car:




Engine rumble removed:




From the engine bay:




Engine rumble removed:
theogre NOV 23, 10:32 AM
Could be valves or exhaust....

Take a piece of hose/tube pointed to exhaust manifold, in oil fill hole, etc & listen on other ends.
That Might tell where the sound come from w/o you getting hands burn.

Oil filter that old can fail in several ways & can leak too.
Worse the media can fail causing dirty oil to run thru it or force bypass in the block to open doing same. (Many GM engines have the filter bypass in the block not in the filter.)

Engine has ~ 4.5-5 quarts of oil & while being 2 quarts low, often doesn't kill the engine but won't help either because oil pickup can suck air when turning the car etc.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Raydar NOV 23, 11:30 AM
In the engine bay recordings, I'm hearing something "random", in addition to a softer - but regular - ticking. The regular ticking sounds like a lifter tick to me. But then, so does an exhaust leak.
What does your oil pressure look like?

Please change your oil and filter.
82-T/A [At Work] NOV 23, 12:05 PM
My thoughts are similar to Ogre's and Raydar on exhaust and lifters.

- An exhaust leak (from a cracked manifold) on the V6 can sound like a ticking noise.
- Failing lifters or a lifter that's not getting enough oil (or with bad lash) can also cause a ticking noise.

Both of these will produce a sound that is consistent with RPMs.


Now... the sound where you have the heading, "From the engine bay:"

That sounds like a similar issue to what my V6 Fiero currently has (as it sits in storage). You can watch that video here...




Like the audio from that sound recording, you have an intermittent sound that is inconsistent with engine RPM. That's the same as mine. To be completely honest, I never did figure out what caused this sound. It didn't affect engine performance... that I'm aware of, but I don't know. I have some thoughts that I wiped a cam-lobe, but I think the rattle would be consistent with engine speed. My guess is that it possibly has something to do with the torque converter (mine is an automatic), and likely either loose torque converter bolts, or possibly something rattling in the catalytic converter. Either of those would largely be inconsistent with the general rhythm of the engine.
lateFormula NOV 23, 12:37 PM
A ticking sound like that can be one of four things:
1) Ignition wire that is loose at either the distributor cap, or on a plug. The ticking would be the slightly muffled sound of the arc. This would be the easiest to diagnose.
2) Exhaust leak. Should be the second easiest to diagnose.
3) Valvetrain noise, probably the most difficult/time consuming to accurately diagnose and pinpoint.
4) Rod knock. Of the three options here, this would fall between exhaust leak and valvetrain for difficulty to diagnose. But it would still be a bit of a job.

[This message has been edited by lateFormula (edited 11-23-2023).]

Spoon NOV 23, 08:21 PM
Could be a deep engine knock in my opinion. To confirm, you could pull a plug wire off briefly (at the boot) to see if the knocking sound is reduced. Try this with each cylinder. Could be lifter noise, timing chain/gear, exhaust leak, etc. Be sure to use a tool with insulated handle to avoid getting shocked.

Spoon

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"Kilgore Trout once wrote a short story which was a dialogue between two pieces of yeast. They were discussing the possible purposes of life as they ate sugar and suffocated in their own excrement. Because of their limited intelligence, they never came close to guessing that they were making champagne." - Kurt Vonnegut

[This message has been edited by Spoon (edited 11-23-2023).]

theogre NOV 23, 09:25 PM

quote
Originally posted by Spoon:
Could be a deep engine knock in my opinion. To confirm, you could pull a plug wire off briefly (at the boot) to see if the knocking sound is reduced. Try this with each cylinder. Could be lifter noise, timing chain/gear, exhaust leak, etc. Be sure to use a tool with insulated handle to avoid getting shocked.

Doing this could help finding a noise & cause Ignition problems because High Volts need a good path to ground or will find another path that can fry the coil, ICM, etc. in milliseconds.

You can use an ignition tester & then run the engine & repeat by shut off, move tester to another plug, run again.
Many types of tester available but I like one that is a mod'ed spark plug,,,
Cliff Pennock NOV 27, 05:30 AM
I've been really busy these past few days so haven't been able to do some more diagnosing. I have driven the car for a few short trips (again, around 20-30 miles) and don't notice any performance issues. But again, I drive my car very conservatively. But my real concern is if I should drive the car at all until I have found the problem...